RE: To use SAME or NOT for High End Storage Setup ? .... Stripe Unit Size 32 MB Vs. 64 KB ?

  • From: Chris Dunscombe <chris@xxxxxxxxxxxxxxxxxxxxx>
  • To: VIVEK_SHARMA@xxxxxxxxxxx
  • Date: Mon, 15 May 2006 09:21:42 +0100

Hi,

My experience, for what it's worth, has been to use 4 MB stripe size using the
volume manager. I've done this on HP-UX with both an IBM Shark arrary and an
EMC Symmetrix array. In both cases performance was fine and there were no "hot"
disks. The logic for choosing 4 MB was to ensure that any full table scans (in
our case 128 KB) would avoid having the multi-block reads split into two reads
due to the required blocks existing in more than 1 "stripe".

We didn't get the chance to test using different stripe sizes.

IMHO I'm not sure why IBM are recommending why you should go as large as 32 MB.

Cheers,

Chris


Quoting VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx>:

Folks



1) IBM is recommending SAME (Stripe across all the 46 LUNs) + 2 separate
LUNs for online redo logfiles



2) IBM is recommending 32 MB Stripe Unit size across the 46 LUNs using
Volume Manager.

NOTE - Each underlying LUN has 8 Disks (Hardware Raid 1+0 with Stripe
Unit Size 64 KB - This is NOT changeable)

Qs. Any feedback on impact of 32 MB Stripe Unit Size(across LUNs) on
Performance of OLTP / Batch Transactions?



For now we are also considering doing a Comparative benchmark of
Performance of 32 MB versus 64 KB Stripe Unit sizes across the 46 LUNs.

NOTE - We may NOT be able to do an exhaustive comparison. Hence any
similar experiences would help very much.



NOTE - In a previous VERY Small benchmark on a few CPUs machine & a Very
Small Storage Box having just a Few Disks with single Software
Striping(NO Hardware Striping) , Performance of our Application's Batch
Runs was VERY POOR for Stripe Unit Sizes of  512 KB, 1 MB, 2 MB.
Performance was Good for Stripe unit Sizes of 64 KB & 128 KB.



Chris Dunscombe

www.christallize.com

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