Re: Fastest Chunk Size w/XFS For MD Software RAID = 1024k

[Peter Rabbitson <rabbit@rabbit.us>]

Justin Piszcz wrote:
> 
> On Thu, 28 Jun 2007, Peter Rabbitson wrote:
> 
>> Interesting, I came up with the same results (1M chunk being superior) 
>> with a completely different raid set with XFS on top:
>>
>> ...
>>
>> Could it be attributed to XFS itself?
>>
>> Peter
>>
> 
> Good question, by the way how much cache do the drives have that you are 
> testing with?
> 

I believe 8MB, but I am not sure I am looking at the right number:

root@Arzamas:~# hdparm -i /dev/sda

/dev/sda:

  Model=aMtxro7 2Y050M                          , FwRev=AY5RH10W, 
SerialNo=6YB6Z7E4
  Config={ Fixed }
  RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
  BuffType=DualPortCache, BuffSize=7936kB, MaxMultSect=16, MultSect=?0?
  CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=268435455
  IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
  PIO modes:  pio0 pio1 pio2 pio3 pio4
  DMA modes:  mdma0 mdma1 mdma2
  UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5
  AdvancedPM=yes: disabled (255) WriteCache=enabled
  Drive conforms to: ATA/ATAPI-7 T13 1532D revision 0:  ATA/ATAPI-1 
ATA/ATAPI-2 ATA/ATAPI-3 ATA/ATAPI-4 ATA/ATAPI-5 ATA/ATAPI-6 ATA/ATAPI-7

  * signifies the current active mode

root@Arzamas:~#

1M chunk consistently delivered best performance with:

o A plain dumb dd run
o bonnie
o two bonnie threads
o iozone with 4 threads

My RA is set at 256 for the drives and 16384 for the array (128k and 8M 
respectively)