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From: Brady Chang <bchang@greenplum.com>
To: "xfs@oss.sgi.com" <xfs@oss.sgi.com>
Subject: fragmentation question
Date: Tue, 7 Sep 2010 17:45:41 -0700	[thread overview]
Message-ID: <C8AC2AC5.6CA9%bchang@greenplum.com> (raw)


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Hello All,
I have an issue with fragmentation on a particular device
thanks for any advice.

-Brady

I have a Dell r510 with 12 disks
2xraid 5 (6 disks each)
raid group1:
48 GB   carved out for os mounted as /
remaining space  2.7 TB for xfs mounted as /data1
raid group2:
48 GB  for swap
remaining space 2.7 TB for xfs mounted as /data2

The strange thing is that /data1 never gets fragmented where as /data2 is badly fragmented.
I believe increase allocsize would help, but not sure how to explain why /data2(/dev/sdd) always gets fragmented and not /data1(/dev/sdb)

It's a data warehouse application.  the I/O is balanced between /data1 and /data2:
output of xfs_db
[root@sdw4 data1]# xfs_db -c frag -r /dev/sdb
actual 14353, ideal 13702, fragmentation factor 4.54%
[root@sdw4 data1]# xfs_db -c frag -r /dev/sdd
actual 408674, ideal 13719, fragmentation factor 96.64%
df output
/dev/sdb              2.7T  967G  1.8T  36% /data1
/dev/sdd              2.7T  1.1T  1.7T  39% /data2

LABEL=/data1        /data1     xfs     allocsize=1048576,logbufs=8,noatime,nodiratime 0 0
LABEL=/data2        /data2     xfs     allocsize=1048576,logbufs=8,noatime,nodiratime 0 0


raid config output:
[root@sdw4 data1]# omreport storage vdisk
List of Virtual Disks in the System

Controller PERC H700 Integrated (Slot 4)
ID                        : 0
Status                    : Ok
Name                      : boot
State                     : Ready
Hot Spare Policy violated : Not Assigned
Virtual Disk Bad Blocks   : No
Secured                   : Not Applicable
Progress                  : Not Applicable
Layout                    : RAID-5
Size                      : 48.99 GB (52602470400 bytes)
Device Name               : /dev/sda
Bus Protocol              : SAS
Media                     : HDD
Read Policy               : No Read Ahead
Write Policy              : Force Write Back
Cache Policy              : Not Applicable
Stripe Element Size       : 128 KB
Disk Cache Policy         : Disabled

ID                        : 1
Status                    : Ok
Name                      : data1
State                     : Ready
Hot Spare Policy violated : Not Assigned
Virtual Disk Bad Blocks   : No
Secured                   : Not Applicable
Progress                  : Not Applicable
Layout                    : RAID-5
Size                      : 2,742.89 GB (2945150484480 bytes)
Device Name               : /dev/sdb
Bus Protocol              : SAS
Media                     : HDD
Read Policy               : No Read Ahead
Write Policy              : Force Write Back
Cache Policy              : Not Applicable
Stripe Element Size       : 128 KB
Disk Cache Policy         : Disabled

ID                        : 2
Status                    : Ok
Name                      : swap
State                     : Ready
Hot Spare Policy violated : Not Assigned
Virtual Disk Bad Blocks   : No
Secured                   : Not Applicable
Progress                  : Not Applicable
Layout                    : RAID-5
Size                      : 48.99 GB (52602470400 bytes)
Device Name               : /dev/sdc
Bus Protocol              : SAS
Media                     : HDD
Read Policy               : No Read Ahead
Write Policy              : Force Write Back
Cache Policy              : Not Applicable
Stripe Element Size       : 128 KB
Disk Cache Policy         : Disabled

ID                        : 3
Status                    : Ok
Name                      : data2
State                     : Ready
Hot Spare Policy violated : Not Assigned
Virtual Disk Bad Blocks   : No
Secured                   : Not Applicable
Progress                  : Not Applicable
Layout                    : RAID-5
Size                      : 2,742.89 GB (2945150484480 bytes)
Device Name               : /dev/sdd
Bus Protocol              : SAS
Media                     : HDD
Read Policy               : No Read Ahead
Write Policy              : Force Write Back
Cache Policy              : Not Applicable
Stripe Element Size       : 128 KB
Disk Cache Policy         : Disabled

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             reply	other threads:[~2010-09-08  0:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-08  0:45 Brady Chang [this message]
2010-09-08  1:16 ` fragmentation question Brady Chang
2010-09-08  7:10 ` Emmanuel Florac
2010-09-09 14:12 ` Eric Sandeen
2010-09-09 21:59   ` Brady Chang
2010-09-09 22:06     ` Eric Sandeen
2010-09-09 23:41       ` Brady Chang
2010-09-10  3:23     ` Stan Hoeppner
2010-09-10  4:57       ` Stan Hoeppner
2010-09-09 23:44   ` Brady Chang

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