Windows 2008 disk I/O size?

[ArystorAaron]

good morning folks:

i was running some tests with IOMeter and diskercise when connected to
a RAID shelf. the shelf has an intelligent SPC-3 compliant hardware/
firmware RAID controller.

with IOMeter, when doing I/O of 1M, 100% Sequential, 100% Write, i
noticed that SRBs were created using DataTransferLength of 1020K
followed by a transfer of 4K. so, no transfers occur with 1024K!

now, this is misleading since IOMeter is effectively not doing what it
should do, sending SRBs of 1024K to disk. instead, we get 2 transfers
of 1020K followed by a 4K transfer.

btw, the same happens with diskercise.

pls also note that i am using Windows MPIO on Windows Server 2008. i
am using another DSM but i know that its Windows sending SRBs with odd
sizes to the DSM because i trapped the request to the DSM using WinDBG
at the DSM's entry point.

Test Setup
- Windows Server 2008 with latest updates
- Qlogic Fibre Channel (FC) HBA QLA2342 2G
- Windows MPIO
- 2 fibres connected between 2 HBA ports to 2 RAID controller ports

if you need any more information, pls let me know.

the same results are also obtained on another machines with QLA2462 4G
HBA.

this is an important observation since IOMeter is used everywhere for
important testing.

cheers!

Aaron
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[eyal...@gmail.com]

Hi Aaron,
It's been a while since this post...

Did you ever get an answer for this issue?

thanks,
Eyal