strange mirror write perf

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* strange mirror write perf
       [not found] ` <6ec5f2dbefa2b7489d9f39d4833d5113@grim-is-a-geek.fr>
@ 2017-03-19 15:14   ` Youenn Gestin
  2017-03-19 23:42     ` Adam Goryachev
  2017-03-20  0:53     ` Peter Grandi
  0 siblings, 2 replies; 5+ messages in thread
From: Youenn Gestin @ 2017-03-19 15:14 UTC (permalink / raw)
  To: linux-raid

Hello,

I'm encountering a drop of write performance after creating a mirror 
with two whole disk ( sdc and sdd ) and i'm not able to find where it 
come from:

Perf before :
abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdd conv=fdatasync
2024+0 records in
2024+0 records out
2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,1238 s, 150 MB/s
abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdc conv=fdatasync
2024+0 records in
2024+0 records out
2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,7046 s, 144 MB/s

Creating the mirror :
abyss ~ # mdadm --create --verbose /dev/md/md6to --level=1
--raid-devices=2 /dev/sdc /dev/sdd
mdadm: Note: this array has metadata at the start and
     may not be suitable as a boot device.  If you plan to
     store '/boot' on this device please ensure that
     your boot-loader understands md/v1.x metadata, or use
     --metadata=0.90
mdadm: size set to 5860391488K
mdadm: automatically enabling write-intent bitmap on large array
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md/md6to started.

Perf after :
abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to 
conv=fdatasync
2024+0 records in
2024+0 records out
2122317824 bytes (2,1 GB, 2,0 GiB) copied, 21,1528 s, 100 MB/s

I've also tried with a mirror created on two partition and the result
was the same.
I tried with a LVM mirror, the drop of performance was not so important 
:

abyss ~ # vgcreate data_vg /dev/sdc
   Physical volume "/dev/sdc" successfully created.
   Volume group "data_vg" successfully created
abyss ~ # vgextend data_vg /dev/sdd
   Physical volume "/dev/sdd" successfully created.
   Volume group "data_vg" successfully extended
abyss ~ # vgs
   VG      #PV #LV #SN Attr   VSize  VFree
   data_vg   2   0   0 wz--n- 10,92t 10,92t
abyss ~ # lvcreate -L 50G -m1 -n lv_mirror data_vg
   Logical volume "lv_mirror" created.
abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/data_vg/lv_mirror
conv=fdatasync
2024+0 records in
2024+0 records out
2122317824 bytes (2,1 GB, 2,0 GiB) copied, 16,3757 s, 130 MB/s

I didn't notice anything wrong while launching the dd test and watching 
top.

Here are the information from asked
https://raid.wiki.kernel.org/index.php/Asking_for_help

abyss lsdrv # smartctl --xall /dev/sdc
smartctl 6.5 2016-05-07 r4318 [x86_64-linux-4.10.2-gentoo] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, 
www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Red
Device Model:     WDC WD60EFRX-68L0BN1
Serial Number:    WD-WX11D76EPFJV
LU WWN Device Id: 5 0014ee 2b88cbb3d
Firmware Version: 82.00A82
User Capacity:    6 001 175 126 016 bytes [6,00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5700 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2, ACS-3 T13/2161-D revision 3b
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is:    Fri Mar 17 14:41:32 2017 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
AAM feature is:   Unavailable
APM feature is:   Unavailable
Rd look-ahead is: Enabled
Write cache is:   Enabled
ATA Security is:  Disabled, frozen [SEC2]
Wt Cache Reorder: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x00) Offline data collection activity
                                         was never started.
                                         Auto Offline Data Collection: 
Disabled.
Self-test execution status:      (   0) The previous self-test routine 
completed
                                         without error or no self-test 
has ever
                                         been run.
Total time to complete Offline
data collection:                ( 8144) seconds.
Offline data collection
capabilities:                    (0x7b) SMART execute Offline immediate.
                                         Auto Offline data collection
on/off support.
                                         Suspend Offline collection upon 
new
                                         command.
                                         Offline surface scan supported.
                                         Self-test supported.
                                         Conveyance Self-test supported.
                                         Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                                         power-saving mode.
                                         Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                                         General Purpose Logging 
supported.
Short self-test routine
recommended polling time:        (   2) minutes.
Extended self-test routine
recommended polling time:        ( 735) minutes.
Conveyance self-test routine
recommended polling time:        (   5) minutes.
SCT capabilities:              (0x303d) SCT Status supported.
                                         SCT Error Recovery Control 
supported.
                                         SCT Feature Control supported.
                                         SCT Data Table supported.

SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAGS    VALUE WORST THRESH FAIL RAW_VALUE
   1 Raw_Read_Error_Rate     POSR-K   200   200   051    -    0
   3 Spin_Up_Time            POS--K   208   208   021    -    8558
   4 Start_Stop_Count        -O--CK   100   100   000    -    12
   5 Reallocated_Sector_Ct   PO--CK   200   200   140    -    0
   7 Seek_Error_Rate         -OSR-K   200   200   000    -    0
   9 Power_On_Hours          -O--CK   100   100   000    -    274
  10 Spin_Retry_Count        -O--CK   100   253   000    -    0
  11 Calibration_Retry_Count -O--CK   100   253   000    -    0
  12 Power_Cycle_Count       -O--CK   100   100   000    -    12
192 Power-Off_Retract_Count -O--CK   200   200   000    -    6
193 Load_Cycle_Count        -O--CK   200   200   000    -    25
194 Temperature_Celsius     -O---K   119   111   000    -    33
196 Reallocated_Event_Count -O--CK   200   200   000    -    0
197 Current_Pending_Sector  -O--CK   200   200   000    -    0
198 Offline_Uncorrectable   ----CK   100   253   000    -    0
199 UDMA_CRC_Error_Count    -O--CK   200   200   000    -    0
200 Multi_Zone_Error_Rate   ---R--   100   253   000    -    0
                             ||||||_ K auto-keep
                             |||||__ C event count
                             ||||___ R error rate
                             |||____ S speed/performance
                             ||_____ O updated online
                             |______ P prefailure warning

General Purpose Log Directory Version 1
SMART           Log Directory Version 1 [multi-sector log support]
Address    Access  R/W   Size  Description
0x00       GPL,SL  R/O      1  Log Directory
0x01           SL  R/O      1  Summary SMART error log
0x02           SL  R/O      5  Comprehensive SMART error log
0x03       GPL     R/O      6  Ext. Comprehensive SMART error log
0x06           SL  R/O      1  SMART self-test log
0x07       GPL     R/O      1  Extended self-test log
0x09           SL  R/W      1  Selective self-test log
0x10       GPL     R/O      1  SATA NCQ Queued Error log
0x11       GPL     R/O      1  SATA Phy Event Counters log
0x21       GPL     R/O      1  Write stream error log
0x22       GPL     R/O      1  Read stream error log
0x30       GPL,SL  R/O      9  IDENTIFY DEVICE data log
0x80-0x9f  GPL,SL  R/W     16  Host vendor specific log
0xa0-0xa7  GPL,SL  VS      16  Device vendor specific log
0xa8-0xb6  GPL,SL  VS       1  Device vendor specific log
0xb7       GPL,SL  VS      54  Device vendor specific log
0xbd       GPL,SL  VS       1  Device vendor specific log
0xc0       GPL,SL  VS       1  Device vendor specific log
0xc1       GPL     VS      93  Device vendor specific log
0xe0       GPL,SL  R/W      1  SCT Command/Status
0xe1       GPL,SL  R/W      1  SCT Data Transfer

SMART Extended Comprehensive Error Log Version: 1 (6 sectors)
No Errors Logged

SMART Extended Self-test Log Version: 1 (1 sectors)
No self-tests have been logged.  [To run self-tests, use: smartctl -t]

SMART Selective self-test log data structure revision number 1
  SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
     1        0        0  Not_testing
     2        0        0  Not_testing
     3        0        0  Not_testing
     4        0        0  Not_testing
     5        0        0  Not_testing
Selective self-test flags (0x0):
   After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute 
delay.

SCT Status Version:                  3
SCT Version (vendor specific):       258 (0x0102)
SCT Support Level:                   1
Device State:                        Active (0)
Current Temperature:                    33 Celsius
Power Cycle Min/Max Temperature:     32/41 Celsius
Lifetime    Min/Max Temperature:     17/41 Celsius
Under/Over Temperature Limit Count:   0/0
Vendor specific:
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

SCT Temperature History Version:     2
Temperature Sampling Period:         1 minute
Temperature Logging Interval:        1 minute
Min/Max recommended Temperature:      0/60 Celsius
Min/Max Temperature Limit:           -41/85 Celsius
Temperature History Size (Index):    478 (193)

Index    Estimated Time   Temperature Celsius
  194    2017-03-17 06:44    32  *************
  ...    ..(464 skipped).    ..  *************
  181    2017-03-17 14:29    32  *************
  182    2017-03-17 14:30    33  **************
  ...    ..( 10 skipped).    ..  **************
  193    2017-03-17 14:41    33  **************

SCT Error Recovery Control:
            Read:     70 (7,0 seconds)
           Write:     70 (7,0 seconds)

Device Statistics (GP/SMART Log 0x04) not supported

SATA Phy Event Counters (GP Log 0x11)
ID      Size     Value  Description
0x0001  2            0  Command failed due to ICRC error
0x0002  2           13  R_ERR response for data FIS
0x0003  2            0  R_ERR response for device-to-host data FIS
0x0004  2           13  R_ERR response for host-to-device data FIS
0x0005  2            0  R_ERR response for non-data FIS
0x0006  2            0  R_ERR response for device-to-host non-data FIS
0x0007  2            0  R_ERR response for host-to-device non-data FIS
0x0008  2            0  Device-to-host non-data FIS retries
0x0009  2           15  Transition from drive PhyRdy to drive PhyNRdy
0x000a  2           30  Device-to-host register FISes sent due to a 
COMRESET
0x000b  2            8  CRC errors within host-to-device FIS
0x000d  2            5  Non-CRC errors within host-to-device FIS
0x000f  2            8  R_ERR response for host-to-device data FIS, CRC
0x0012  2            0  R_ERR response for host-to-device non-data FIS, 
CRC
0x8000  4       318448  Vendor specific

-------------------------------------------------------------------------------

abyss lsdrv # smartctl --xall /dev/sdd
smartctl 6.5 2016-05-07 r4318 [x86_64-linux-4.10.2-gentoo] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, 
www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Red
Device Model:     WDC WD60EFRX-68L0BN1
Serial Number:    WD-WX41D964EZK9
LU WWN Device Id: 5 0014ee 263752a6e
Firmware Version: 82.00A82
User Capacity:    6 001 175 126 016 bytes [6,00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5700 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2, ACS-3 T13/2161-D revision 3b
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Fri Mar 17 14:41:57 2017 CET
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
AAM feature is:   Unavailable
APM feature is:   Unavailable
Rd look-ahead is: Enabled
Write cache is:   Enabled
ATA Security is:  Disabled, frozen [SEC2]
Wt Cache Reorder: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x00) Offline data collection activity
                                         was never started.
                                         Auto Offline Data Collection: 
Disabled.
Self-test execution status:      (   0) The previous self-test routine 
completed
                                         without error or no self-test 
has ever
                                         been run.
Total time to complete Offline
data collection:                ( 9344) seconds.
Offline data collection
capabilities:                    (0x7b) SMART execute Offline immediate.
                                         Auto Offline data collection
on/off support.
                                         Suspend Offline collection upon 
new
                                         command.
                                         Offline surface scan supported.
                                         Self-test supported.
                                         Conveyance Self-test supported.
                                         Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                                         power-saving mode.
                                         Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                                         General Purpose Logging 
supported.
Short self-test routine
recommended polling time:        (   2) minutes.
Extended self-test routine
recommended polling time:        ( 746) minutes.
Conveyance self-test routine
recommended polling time:        (   5) minutes.
SCT capabilities:              (0x303d) SCT Status supported.
                                         SCT Error Recovery Control 
supported.
                                         SCT Feature Control supported.
                                         SCT Data Table supported.

SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAGS    VALUE WORST THRESH FAIL RAW_VALUE
   1 Raw_Read_Error_Rate     POSR-K   200   200   051    -    0
   3 Spin_Up_Time            POS--K   100   253   021    -    0
   4 Start_Stop_Count        -O--CK   100   100   000    -    5
   5 Reallocated_Sector_Ct   PO--CK   200   200   140    -    0
   7 Seek_Error_Rate         -OSR-K   100   253   000    -    0
   9 Power_On_Hours          -O--CK   100   100   000    -    246
  10 Spin_Retry_Count        -O--CK   100   253   000    -    0
  11 Calibration_Retry_Count -O--CK   100   253   000    -    0
  12 Power_Cycle_Count       -O--CK   100   100   000    -    5
192 Power-Off_Retract_Count -O--CK   200   200   000    -    1
193 Load_Cycle_Count        -O--CK   200   200   000    -    19
194 Temperature_Celsius     -O---K   121   116   000    -    31
196 Reallocated_Event_Count -O--CK   200   200   000    -    0
197 Current_Pending_Sector  -O--CK   200   200   000    -    0
198 Offline_Uncorrectable   ----CK   100   253   000    -    0
199 UDMA_CRC_Error_Count    -O--CK   200   200   000    -    0
200 Multi_Zone_Error_Rate   ---R--   100   253   000    -    0
                             ||||||_ K auto-keep
                             |||||__ C event count
                             ||||___ R error rate
                             |||____ S speed/performance
                             ||_____ O updated online
                             |______ P prefailure warning

General Purpose Log Directory Version 1
SMART           Log Directory Version 1 [multi-sector log support]
Address    Access  R/W   Size  Description
0x00       GPL,SL  R/O      1  Log Directory
0x01           SL  R/O      1  Summary SMART error log
0x02           SL  R/O      5  Comprehensive SMART error log
0x03       GPL     R/O      6  Ext. Comprehensive SMART error log
0x04       GPL,SL  R/O      8  Device Statistics log
0x06           SL  R/O      1  SMART self-test log
0x07       GPL     R/O      1  Extended self-test log
0x09           SL  R/W      1  Selective self-test log
0x0c       GPL     R/O   2048  Pending Defects log
0x10       GPL     R/O      1  SATA NCQ Queued Error log
0x11       GPL     R/O      1  SATA Phy Event Counters log
0x21       GPL     R/O      1  Write stream error log
0x22       GPL     R/O      1  Read stream error log
0x30       GPL,SL  R/O      9  IDENTIFY DEVICE data log
0x80-0x9f  GPL,SL  R/W     16  Host vendor specific log
0xa0-0xa7  GPL,SL  VS      16  Device vendor specific log
0xa8-0xb6  GPL,SL  VS       1  Device vendor specific log
0xb7       GPL,SL  VS      54  Device vendor specific log
0xbd       GPL,SL  VS       1  Device vendor specific log
0xc0       GPL,SL  VS       1  Device vendor specific log
0xc1       GPL     VS      93  Device vendor specific log
0xe0       GPL,SL  R/W      1  SCT Command/Status
0xe1       GPL,SL  R/W      1  SCT Data Transfer

SMART Extended Comprehensive Error Log Version: 1 (6 sectors)
No Errors Logged

SMART Extended Self-test Log Version: 1 (1 sectors)
No self-tests have been logged.  [To run self-tests, use: smartctl -t]

SMART Selective self-test log data structure revision number 1
  SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
     1        0        0  Not_testing
     2        0        0  Not_testing
     3        0        0  Not_testing
     4        0        0  Not_testing
     5        0        0  Not_testing
Selective self-test flags (0x0):
   After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute 
delay.

SCT Status Version:                  3
SCT Version (vendor specific):       258 (0x0102)
SCT Support Level:                   1
Device State:                        Active (0)
Current Temperature:                    31 Celsius
Power Cycle Min/Max Temperature:     30/36 Celsius
Lifetime    Min/Max Temperature:     16/36 Celsius
Under/Over Temperature Limit Count:   0/0
Vendor specific:
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

SCT Temperature History Version:     2
Temperature Sampling Period:         1 minute
Temperature Logging Interval:        1 minute
Min/Max recommended Temperature:      0/60 Celsius
Min/Max Temperature Limit:           -41/85 Celsius
Temperature History Size (Index):    478 (434)

Index    Estimated Time   Temperature Celsius
  435    2017-03-17 06:44    30  ***********
  ...    ..(463 skipped).    ..  ***********
  421    2017-03-17 14:28    30  ***********
  422    2017-03-17 14:29    31  ************
  ...    ..( 11 skipped).    ..  ************
  434    2017-03-17 14:41    31  ************

SCT Error Recovery Control:
            Read:     70 (7,0 seconds)
           Write:     70 (7,0 seconds)

Device Statistics (GP Log 0x04)
Page  Offset Size        Value Flags Description
0x01  =====  =               =  ===  == General Statistics (rev 2) ==
0x01  0x008  4               5  ---  Lifetime Power-On Resets
0x01  0x010  4             246  ---  Power-on Hours
0x01  0x018  6     23708519208  ---  Logical Sectors Written
0x01  0x020  6        24687968  ---  Number of Write Commands
0x01  0x028  6     11729201720  ---  Logical Sectors Read
0x01  0x030  6        22155003  ---  Number of Read Commands
0x03  =====  =               =  ===  == Rotating Media Statistics (rev 
1) ==
0x03  0x008  4             246  ---  Spindle Motor Power-on Hours
0x03  0x010  4              43  ---  Head Flying Hours
0x03  0x018  4              21  ---  Head Load Events
0x03  0x020  4               0  ---  Number of Reallocated Logical 
Sectors
0x03  0x028  4               0  ---  Read Recovery Attempts
0x03  0x030  4               0  ---  Number of Mechanical Start Failures
0x04  =====  =               =  ===  == General Errors Statistics (rev 
1) ==
0x04  0x008  4               0  ---  Number of Reported Uncorrectable 
Errors
0x04  0x010  4               0  ---  Resets Between Cmd Acceptance and
Completion
0x05  =====  =               =  ===  == Temperature Statistics (rev 1) 
==
0x05  0x008  1              31  ---  Current Temperature
0x05  0x010  1              30  ---  Average Short Term Temperature
0x05  0x018  1               -  ---  Average Long Term Temperature
0x05  0x020  1              36  ---  Highest Temperature
0x05  0x028  1              19  ---  Lowest Temperature
0x05  0x030  1              33  ---  Highest Average Short Term 
Temperature
0x05  0x038  1              30  ---  Lowest Average Short Term 
Temperature
0x05  0x040  1               -  ---  Highest Average Long Term 
Temperature
0x05  0x048  1               -  ---  Lowest Average Long Term 
Temperature
0x05  0x050  4               0  ---  Time in Over-Temperature
0x05  0x058  1              60  ---  Specified Maximum Operating 
Temperature
0x05  0x060  4               0  ---  Time in Under-Temperature
0x05  0x068  1               0  ---  Specified Minimum Operating 
Temperature
0x06  =====  =               =  ===  == Transport Statistics (rev 1) ==
0x06  0x008  4              22  ---  Number of Hardware Resets
0x06  0x010  4               3  ---  Number of ASR Events
0x06  0x018  4               0  ---  Number of Interface CRC Errors
                                 |||_ C monitored condition met
                                 ||__ D supports DSN
                                 |___ N normalized value

SATA Phy Event Counters (GP Log 0x11)
ID      Size     Value  Description
0x0001  2            0  Command failed due to ICRC error
0x0002  2            0  R_ERR response for data FIS
0x0003  2            0  R_ERR response for device-to-host data FIS
0x0004  2            0  R_ERR response for host-to-device data FIS
0x0005  2            0  R_ERR response for non-data FIS
0x0006  2            0  R_ERR response for device-to-host non-data FIS
0x0007  2            0  R_ERR response for host-to-device non-data FIS
0x0008  2            0  Device-to-host non-data FIS retries
0x0009  2            2  Transition from drive PhyRdy to drive PhyNRdy
0x000a  2            4  Device-to-host register FISes sent due to a 
COMRESET
0x000b  2            0  CRC errors within host-to-device FIS
0x000d  2            0  Non-CRC errors within host-to-device FIS
0x000f  2            0  R_ERR response for host-to-device data FIS, CRC
0x0012  2            0  R_ERR response for host-to-device non-data FIS, 
CRC
0x8000  4       318477  Vendor specific


abyss lsdrv # mdadm --examine /dev/sdc
/dev/sdc:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 183ad93e:c604b817:7099c950:12d36bab
            Name : abyss:md6to  (local to host abyss)
   Creation Time : Mon Mar 13 22:11:47 2017
      Raid Level : raid1
    Raid Devices : 2

  Avail Dev Size : 11720783024 (5588.90 GiB 6001.04 GB)
      Array Size : 5860391488 (5588.90 GiB 6001.04 GB)
   Used Dev Size : 11720782976 (5588.90 GiB 6001.04 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=48 sectors
           State : clean
     Device UUID : b55a87f4:15d145d1:19979cc5:e1eafc32

Internal Bitmap : 8 sectors from superblock
     Update Time : Fri Mar 17 14:24:32 2017
   Bad Block Log : 512 entries available at offset 32 sectors
        Checksum : b949b844 - correct
          Events : 9925


    Device Role : Active device 1
    Array State : AA ('A' == active, '.' == missing, 'R' == replacing)

-----------------------------------------------------------------------------

abyss lsdrv # mdadm --examine /dev/sdd
/dev/sdd:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : 183ad93e:c604b817:7099c950:12d36bab
            Name : abyss:md6to  (local to host abyss)
   Creation Time : Mon Mar 13 22:11:47 2017
      Raid Level : raid1
    Raid Devices : 2

  Avail Dev Size : 11720783024 (5588.90 GiB 6001.04 GB)
      Array Size : 5860391488 (5588.90 GiB 6001.04 GB)
   Used Dev Size : 11720782976 (5588.90 GiB 6001.04 GB)
     Data Offset : 262144 sectors
    Super Offset : 8 sectors
    Unused Space : before=262064 sectors, after=48 sectors
           State : clean
     Device UUID : ddbae969:eae9cb91:fb7fa642:1932781a

Internal Bitmap : 8 sectors from superblock
     Update Time : Fri Mar 17 14:24:32 2017
   Bad Block Log : 512 entries available at offset 32 sectors
        Checksum : 53b76159 - correct
          Events : 9925


    Device Role : Active device 0
    Array State : AA ('A' == active, '.' == missing, 'R' == replacing)

-----------------------------------------------------------------------------

abyss lsdrv # mdadm --detail /dev/md127
/dev/md127:
         Version : 1.2
   Creation Time : Mon Mar 13 22:11:47 2017
      Raid Level : raid1
      Array Size : 5860391488 (5588.90 GiB 6001.04 GB)
   Used Dev Size : 5860391488 (5588.90 GiB 6001.04 GB)
    Raid Devices : 2
   Total Devices : 2
     Persistence : Superblock is persistent

   Intent Bitmap : Internal

     Update Time : Fri Mar 17 14:24:32 2017
           State : clean
  Active Devices : 2
Working Devices : 2
  Failed Devices : 0
   Spare Devices : 0

            Name : abyss:md6to  (local to host abyss)
            UUID : 183ad93e:c604b817:7099c950:12d36bab
          Events : 9925

     Number   Major   Minor   RaidDevice State
        0       8       48        0      active sync   /dev/sdd
        1       8       32        1      active sync   /dev/sdc

-----------------------------------------------------------------------------

abyss lsdrv # python2.7 lsdrv
PCI [hptiop] 01:00.0 RAID bus controller: HighPoint Technologies, Inc.
Device 3520 (rev 09)
└scsi 0:0:0:0 HPT      VD0-0            {}
  └sda 8.19t [8:0] Partitioned (gpt)
   └sda1 8.19t [8:1] ext4 {7262b140-e026-4b53-bc6b-2ac1c1cc4538}
    └Mounted as /dev/sda1 @ /mnt
PCI [ahci] 00:11.0 SATA controller: Advanced Micro Devices, Inc. [AMD]
FCH SATA Controller [AHCI mode] (rev 40)
├scsi 1:0:0:0 ATA      OCZ-VERTEX4      {OCZ-9NYS802X56U11736}
│└sdb 238.47g [8:16] Partitioned (dos)
│ └sdb1 238.47g [8:17] ext4 {6de79b5d-dc44-4362-86af-b483fbbe1c65}
│  └Mounted as /dev/sdb1 @ /
├scsi 2:0:0:0 ATA      WDC WD60EFRX-68L {WD-WX11D76EPFJV}
│└sdc 5.46t [8:32] MD raid1 (1/2) (w/ sdd) in_sync 'abyss:md6to'
{183ad93e-c604-b817-7099-c95012d36bab}
│ └md127 5.46t [9:127] MD v1.2 raid1 (2) clean
{183ad93e:c604b817:7099c950:12d36bab}
│                      Empty/Unknown
├scsi 3:0:0:0 ATA      WDC WD60EFRX-68L {WD-WX41D964EZK9}
│└sdd 5.46t [8:48] MD raid1 (0/2) (w/ sdc) in_sync 'abyss:md6to'
{183ad93e-c604-b817-7099-c95012d36bab}
│ └md127 5.46t [9:127] MD v1.2 raid1 (2) clean
{183ad93e:c604b817:7099c950:12d36bab}
│                      Empty/Unknown
├scsi 4:x:x:x [Empty]

-----------------------------------------------------------------------------

abyss lsdrv # cat /proc/mdstat
Personalities : [raid1] [raid10] [raid6] [raid5] [raid4]
md127 : active raid1 sdd[0] sdc[1]
       5860391488 blocks super 1.2 [2/2] [UU]
       bitmap: 0/44 pages [0KB], 65536KB chunk

unused devices: <none>

-----------------------------------------------------------------------------

abyss lsdrv # mdadm --version
mdadm - v4.0 - 2017-01-09

-----------------------------------------------------------------------------

abyss lsdrv # uname -a
Linux abyss 4.10.2-gentoo #2 SMP Mon Mar 13 21:46:37 CET 2017 x86_64
AMD A8-5600K APU with Radeon(tm) HD Graphics AuthenticAMD GNU/Linux


Thanks for your help.

Youenn.

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: strange mirror write perf
  2017-03-19 15:14   ` strange mirror write perf Youenn Gestin
@ 2017-03-19 23:42     ` Adam Goryachev
  2017-03-20  0:44       ` Youenn Gestin
  2017-03-20  0:53     ` Peter Grandi
  1 sibling, 1 reply; 5+ messages in thread
From: Adam Goryachev @ 2017-03-19 23:42 UTC (permalink / raw)
  To: Youenn Gestin, linux-raid

On 20/03/17 02:14, Youenn Gestin wrote:
> Hello,
>
> I'm encountering a drop of write performance after creating a mirror 
> with two whole disk ( sdc and sdd ) and i'm not able to find where it 
> come from:
>
> Perf before :
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdd conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,1238 s, 150 MB/s
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdc conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,7046 s, 144 MB/s
>
> Creating the mirror :
> abyss ~ # mdadm --create --verbose /dev/md/md6to --level=1
> --raid-devices=2 /dev/sdc /dev/sdd
> mdadm: Note: this array has metadata at the start and
>     may not be suitable as a boot device.  If you plan to
>     store '/boot' on this device please ensure that
>     your boot-loader understands md/v1.x metadata, or use
>     --metadata=0.90
> mdadm: size set to 5860391488K
> mdadm: automatically enabling write-intent bitmap on large array
> Continue creating array? y
> mdadm: Defaulting to version 1.2 metadata
> mdadm: array /dev/md/md6to started.
>
> Perf after :
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to 
> conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 21,1528 s, 100 MB/s 

Two possible thoughts:
1) Did you wait until the two drives had completed the initial sync 
before testing? "cat /proc/mdstat" will show this.
2) As noted, "mdadm: automatically enabling write-intent bitmap on large 
array" try to disable this to see if you get the results you were expecting.

Other than that, I'm not sure, but please reply, and if it isn't so 
simple, then someone else might jump in.

Regards,
Adam

-- 
Adam Goryachev Website Managers www.websitemanagers.com.au

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: strange mirror write perf
  2017-03-19 23:42     ` Adam Goryachev
@ 2017-03-20  0:44       ` Youenn Gestin
  2017-03-20  5:07         ` Roman Mamedov
  0 siblings, 1 reply; 5+ messages in thread
From: Youenn Gestin @ 2017-03-20  0:44 UTC (permalink / raw)
  To: Adam Goryachev; +Cc: linux-raid

Le 2017-03-20 00:42, Adam Goryachev a écrit :
> On 20/03/17 02:14, Youenn Gestin wrote:
>> Hello,
>> 
>> I'm encountering a drop of write performance after creating a mirror 
>> with two whole disk ( sdc and sdd ) and i'm not able to find where it 
>> come from:
>> 
>> Perf before :
>> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdd conv=fdatasync
>> 2024+0 records in
>> 2024+0 records out
>> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,1238 s, 150 MB/s
>> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdc conv=fdatasync
>> 2024+0 records in
>> 2024+0 records out
>> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,7046 s, 144 MB/s
>> 
>> Creating the mirror :
>> abyss ~ # mdadm --create --verbose /dev/md/md6to --level=1
>> --raid-devices=2 /dev/sdc /dev/sdd
>> mdadm: Note: this array has metadata at the start and
>>     may not be suitable as a boot device.  If you plan to
>>     store '/boot' on this device please ensure that
>>     your boot-loader understands md/v1.x metadata, or use
>>     --metadata=0.90
>> mdadm: size set to 5860391488K
>> mdadm: automatically enabling write-intent bitmap on large array
>> Continue creating array? y
>> mdadm: Defaulting to version 1.2 metadata
>> mdadm: array /dev/md/md6to started.
>> 
>> Perf after :
>> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to 
>> conv=fdatasync
>> 2024+0 records in
>> 2024+0 records out
>> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 21,1528 s, 100 MB/s
> 
> Two possible thoughts:
> 1) Did you wait until the two drives had completed the initial sync
> before testing? "cat /proc/mdstat" will show this.
> 2) As noted, "mdadm: automatically enabling write-intent bitmap on
> large array" try to disable this to see if you get the results you
> were expecting.
> 
> Other than that, I'm not sure, but please reply, and if it isn't so
> simple, then someone else might jump in.
> 
> Regards,
> Adam

Hello,

You got it right on your 2nd tought !
Took a look at 
https://raid.wiki.kernel.org/index.php/Write-intent_bitmap , disabled it 
( mdadm --grow --bitmap=none /dev/md/md6to ) ang here we go :

abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to 
conv=fdatasync
2024+0 records in
2024+0 records out
2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,5074 s, 146 MB/s

I'll check about this function to see if i'll need it or not tomorow,

Thank you !

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: strange mirror write perf
  2017-03-20  0:44       ` Youenn Gestin
@ 2017-03-20  5:07         ` Roman Mamedov
  0 siblings, 0 replies; 5+ messages in thread
From: Roman Mamedov @ 2017-03-20  5:07 UTC (permalink / raw)
  To: Youenn Gestin; +Cc: Adam Goryachev, linux-raid

On Mon, 20 Mar 2017 01:44:09 +0100
Youenn Gestin <youenn.gestin@grim-is-a-geek.fr> wrote:

> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to 
> conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,5074 s, 146 MB/s
> 
> I'll check about this function to see if i'll need it or not tomorow,

Instead of disabling it you can alter the bitmap chunk size, and at larger
chunk sizes it does not affect the performance as much.
http://tgharold.blogspot.fr/2013/01/mdadm-using-bitmaps-to-speed-up-rebuilds.html
For 6TB drives try 256 or even 512MB for the size.

-- 
With respect,
Roman

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: strange mirror write perf
  2017-03-19 15:14   ` strange mirror write perf Youenn Gestin
  2017-03-19 23:42     ` Adam Goryachev
@ 2017-03-20  0:53     ` Peter Grandi
  1 sibling, 0 replies; 5+ messages in thread
From: Peter Grandi @ 2017-03-20  0:53 UTC (permalink / raw)
  To: Linux RAID

[ ... ]
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdd conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,1238 s, 150 MB/s
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/sdc conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 14,7046 s, 144 MB/s
[ ... ]
> mdadm: automatically enabling write-intent bitmap on large array
[ ... ]
> abyss ~ # dd bs=1M count=2024 if=/dev/zero of=/dev/md/md6to conv=fdatasync
> 2024+0 records in
> 2024+0 records out
> 2122317824 bytes (2,1 GB, 2,0 GiB) copied, 21,1528 s, 100 MB/s
[ ... ]

This is not about "performance" but raw speed in a very
particular situation. The difference is not large and could be
meaningless for a variety of reasons:

* Had the initial 6TB sync finished (would take 15-17 hours)?
* Internal bitmaps can steal a fair bit of speed.
* For whatever weirdness is related to the appalling
  implementation of the Linux page cache, IO reading (but less
  so writing) an MD block device is often slower than to a file
  on a filetree on that block device, plus writing via the page
  cache costs a lot of CPU time.

Replication of the experiment on similar smaller disks:

soft#  mdadm --create --verbose /dev/md/md6to --level=1 --raid-devices=2 /dev/sde3 /dev/sdf3
mdadm: size set to 243269440K
mdadm: array /dev/md/md6to started.

soft#  grep -A2 'sd[ef]3' /proc/mdstat 
md127 : active raid1 sdf3[1] sde3[0]
      243269440 blocks super 1.0 [2/2] [UU]
      [====>................]  resync = 20.5% (49954880/243269440) finish=19.5min speed=164445K/sec

soft#  grep -A2 'sd[ef]3' /proc/mdstat; dd bs=1M count=2024 if=/dev/zero of=/dev
/md/md6to conv=fdatasync                                                        
md127 : active raid1 sdf3[1] sde3[0]
      243269440 blocks super 1.0 [2/2] [UU]

2024+0 records in
2024+0 records out
2122317824 bytes (2.1 GB) copied, 13.8561 s, 153 MB/s

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2017-03-20  5:07 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
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2017-03-19 15:14   ` strange mirror write perf Youenn Gestin
2017-03-19 23:42     ` Adam Goryachev
2017-03-20  0:44       ` Youenn Gestin
2017-03-20  5:07         ` Roman Mamedov
2017-03-20  0:53     ` Peter Grandi

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