[linux-lvm] Parallel mirroring

[linux-lvm] Parallel mirroring

[Diego Jacobi]

Hello.

I have succesfully configured Mirroring between 2 disks in linux for 2
logical volumes, and on other without mirroring.
But i can not find any evidence showing that it is reading in parallel
scheduler mode.
I have read HP docs about HP-UX, but it talks about command line
options which arent in the linux side.

The "-d p" in HP-UX would be what i need now for linux. Also lvdisplay
doesnt show anything about it, more than the number of mirrors.


This are my tests:

sda1 = /boot in disk 1, no lvm
sdb1 = /boot in disk 2, no lvm
data/data = lvm without mirroring
data/root = lvm with mirroring


linux-8mmd:~ # hdparm -t /dev/sda1
/dev/sda1:
 Timing buffered disk reads:  262 MB in  3.02 seconds =  86.83 MB/sec

linux-8mmd:~ # hdparm -t /dev/sdb1
/dev/sdb1:
 Timing buffered disk reads:  174 MB in  3.03 seconds =  57.36 MB/sec

linux-8mmd:~ # hdparm -t /dev/data/data
/dev/data/data:
 Timing buffered disk reads:  272 MB in  3.02 seconds =  90.02 MB/sec

linux-8mmd:~ # hdparm -t /dev/data/root
/dev/data/root:
 Timing buffered disk reads:  278 MB in  3.02 seconds =  92.16 MB/sec



As you can see, the read speed are mostly the same. This could mean a
secuenced scheduler.

And this is my system setup:

lvm> version
  LVM version:     2.02.39 (2008-06-27)
  Library version: 1.02.27 (2008-06-25)
  Driver version:  4.14.0

linux-8mmd:~ # pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/sda3  data lvm2 a-   537.11G 395.12G
  /dev/sda5  data lvm2 a-   996.00M 988.00M         <--- Note 1 Gb, for log
  /dev/sdb3  data lvm2 a-   138.99G 118.99G

linux-8mmd:~ # lvs -a -o +devices
  LV              VG   Attr   LSize   Origin Snap%  Move Log
Copy%  Convert Devices
  data            data -wi-ao 121.50G
           /dev/sda3(125)
  home            data mwi-ao  10.00G                    home_mlog
100.00         home_mimage_0(0),home_mimage_1(0)
  [home_mimage_0] data iwi-ao  10.00G
           /dev/sda3(33788)
  [home_mimage_1] data iwi-ao  10.00G
           /dev/sdb3(2560)
  [home_mlog]     data lwi-ao   4.00M
           /dev/sda5(1)
  root            data mwi-ao  10.00G                    root_mlog
100.00         root_mimage_0(0),root_mimage_1(0)
  [root_mimage_0] data iwi-ao  10.00G
           /dev/sda3(31228)
  [root_mimage_1] data iwi-ao  10.00G
           /dev/sdb3(0)
  [root_mlog]     data lwi-ao   4.00M
           /dev/sda5(0)
  test            data -wi-a- 500.00M
           /dev/sda3(0)

[linux-lvm] Re: Parallel mirroring

[Diego Jacobi]

Hi.

Sry for retry but the lvm list is my last resource.

Does Linux-LVM have Parallel scheduler mode for mirroring at all?
If yes, how do you set it up, or check if it is enabled?

Thanks.
Diego



2009/7/12 Diego Jacobi <jacobidiego@gmail.com>:
> Hello.
>
> I have succesfully configured Mirroring between 2 disks in linux for 2
> logical volumes, and on other without mirroring.
> But i can not find any evidence showing that it is reading in parallel
> scheduler mode.
> I have read HP docs about HP-UX, but it talks about command line
> options which arent in the linux side.
>
> The "-d p" in HP-UX would be what i need now for linux. Also lvdisplay
> doesnt show anything about it, more than the number of mirrors.
>
>
> This are my tests:
>
> sda1 = /boot in disk 1, no lvm
> sdb1 = /boot in disk 2, no lvm
> data/data = lvm without mirroring
> data/root = lvm with mirroring
>
>
> linux-8mmd:~ # hdparm -t /dev/sda1
> /dev/sda1:
> �Timing buffered disk reads: �262 MB in �3.02 seconds = �86.83 MB/sec
>
> linux-8mmd:~ # hdparm -t /dev/sdb1
> /dev/sdb1:
> �Timing buffered disk reads: �174 MB in �3.03 seconds = �57.36 MB/sec
>
> linux-8mmd:~ # hdparm -t /dev/data/data
> /dev/data/data:
> �Timing buffered disk reads: �272 MB in �3.02 seconds = �90.02 MB/sec
>
> linux-8mmd:~ # hdparm -t /dev/data/root
> /dev/data/root:
> �Timing buffered disk reads: �278 MB in �3.02 seconds = �92.16 MB/sec
>
>
>
> As you can see, the read speed are mostly the same. This could mean a
> secuenced scheduler.
>
> And this is my system setup:
>
> lvm> version
> �LVM version: � � 2.02.39 (2008-06-27)
> �Library version: 1.02.27 (2008-06-25)
> �Driver version: �4.14.0
>
> linux-8mmd:~ # pvs
> �PV � � � � VG � Fmt �Attr PSize � PFree
> �/dev/sda3 �data lvm2 a- � 537.11G 395.12G
> �/dev/sda5 �data lvm2 a- � 996.00M 988.00M � � � � <--- Note 1 Gb, for log
> �/dev/sdb3 �data lvm2 a- � 138.99G 118.99G
>
> linux-8mmd:~ # lvs -a -o +devices
> �LV � � � � � � �VG � Attr � LSize � Origin Snap% �Move Log
> Copy% �Convert Devices
> �data � � � � � �data -wi-ao 121.50G
> � � � � � /dev/sda3(125)
> �home � � � � � �data mwi-ao �10.00G � � � � � � � � � �home_mlog
> 100.00 � � � � home_mimage_0(0),home_mimage_1(0)
> �[home_mimage_0] data iwi-ao �10.00G
> � � � � � /dev/sda3(33788)
> �[home_mimage_1] data iwi-ao �10.00G
> � � � � � /dev/sdb3(2560)
> �[home_mlog] � � data lwi-ao � 4.00M
> � � � � � /dev/sda5(1)
> �root � � � � � �data mwi-ao �10.00G � � � � � � � � � �root_mlog
> 100.00 � � � � root_mimage_0(0),root_mimage_1(0)
> �[root_mimage_0] data iwi-ao �10.00G
> � � � � � /dev/sda3(31228)
> �[root_mimage_1] data iwi-ao �10.00G
> � � � � � /dev/sdb3(0)
> �[root_mlog] � � data lwi-ao � 4.00M
> � � � � � /dev/sda5(0)
> �test � � � � � �data -wi-a- 500.00M
> � � � � � /dev/sda3(0)
>

Re: [linux-lvm] Re: Parallel mirroring

[malahal]

Diego Jacobi [jacobidiego@gmail.com] wrote:
> Hi.
> 
> Sry for retry but the lvm list is my last resource.

Try dm-devel mailing list. Linux LVM is based on device mapper
framework.

> Does Linux-LVM have Parallel scheduler mode for mirroring at all?
> If yes, how do you set it up, or check if it is enabled?

Writes happen in parallel, of course! At the moment it only reads from
the default mirror leg (unless the default leg is broken). There was
some patch for round-robin reading among mirrored legs, but it is not in
the upstream yet.

--Malahal.