Re: Negligible improvement when using su/sw for hardware RAID5, expected?

[utz lehmann <u.lehmann@de.tecosim.com>]

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Hi

You are using a partition. Is it correctly aligned? Usually the first
partition starts at sector 63. Which is in the middle of your stripe.
Use the whole disk (/dev/sda) or align the start of the partition to a
multiple of the stripe size.
But i doubt you will see a performance improvement with such a simple
test (single threaded sequential read/ write).


utz 

On Fri, 2006-08-11 at 23:10 -0400, Brian Davis wrote:
> Is this expected? I thought I would see more improvement when tweaking 
> my su/sw values for hardware RAID 5.
> 
> Details, 3x300GB drives, 3Ware 7506-4LP Hardware RAID 5 using a 64K 
> stripe size (non-configurable on this card).
> 
> FS creation and Bonnie++ results:
> 
> Untweaked:---------------------------------------------------------------------- 
> 
> 
> localhost / # mkfs.xfs -f /dev/sda1
> meta-data=/dev/sda1              isize=256    agcount=32, agsize=4578999 
> blks
>         =                       sectsz=512   attr=0
> data     =                       bsize=4096   blocks=146527968, imaxpct=25
>         =                       sunit=0      swidth=0 blks, unwritten=1
> naming   =version 2              bsize=4096
> log      =internal log           bsize=4096   blocks=32768, version=1
>         =                       sectsz=512   sunit=0 blks
> realtime =none                   extsz=65536  blocks=0, rtextents=0
> localhost / # mount -t xfs /dev/sda1 /raid
> localhost / # cd /raid
> localhost raid # bonnie++ -n0 -u0 -r 768 -s 30720 -b -f
> Using uid:0, gid:0.
> Writing intelligently...done
> Rewriting...done
> Reading intelligently...done
> start 'em...done...done...done...done...done...
> Version 1.93c       ------Sequential Output------ --Sequential Input- 
> --Random-
> Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- 
> --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  
> /sec %CP
> localhost       30G           27722  40 23847  37           98367  99  
> 88.6  11
> Latency                         891ms     693ms             16968us     
> 334ms
> 
> Tweaked:------------------------------------------------------------------------- 
> 
> 
> localhost / # mkfs.xfs -f -d sw=2,su=64k /dev/sda1
> meta-data=/dev/sda1              isize=256    agcount=32, agsize=4578992 
> blks
>         =                       sectsz=512   attr=0
> data     =                       bsize=4096   blocks=146527744, imaxpct=25
>         =                       sunit=16     swidth=32 blks, unwritten=1
> naming   =version 2              bsize=4096
> log      =internal log           bsize=4096   blocks=32768, version=1
>         =                       sectsz=512   sunit=0 blks
> realtime =none                   extsz=65536  blocks=0, rtextents=0
> localhost / # mount -t xfs /dev/sda1 /raid
> localhost / # cd /raid
> localhost raid # bonnie++ -n0 -u0 -r 768 -s 30720 -b -f
> Using uid:0, gid:0.
> Writing intelligently...done
> Rewriting...done
> Reading intelligently...done
> start 'em...done...done...done...done...done...
> Version 1.93c       ------Sequential Output------ --Sequential Input- 
> --Random-
> Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- 
> --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  
> /sec %CP
> localhost       30G           27938  43 23880  40           98066  99  
> 91.8   9
> Latency                         772ms     584ms             19889us     
> 340ms
> 
-- 
    <>        utz lehmann
  <>  <>      u.lehmann@de.tecosim.com
<>  <>  <>    TECOSIM GmbH / IT
  <>  <>      +49(0)-6142-82720
    <>        http://www.tecosim.com/


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