Sluggish disk volumes

[Per Kr. Meyer]

Yess, the stripe size is 16k.
I can't alter this without rebuilding the RAID from scratch.
To what extent will this fact impact performance ?
Stripesize 16k vs 64k

[Per Kr. Meyer]

And by the way :
The RAID controller says it's a SMART RAID 5i. No "plus". Yet it states that cache memory is equally devided between read and write (24576KB on each). It says battery pack count 1 and battery status ok. Should be safe to enable write cache, or..... ?

[Ryan Goff]

Ok, so it seems I was right about your stripe size. Your 5i controller defaulted to 16k size for your Raid 5 when you installed the server. HP has changed this default value on the newer controllers as they have found that it performs better at a 64k value.

You can easily migrate to 64k stripe size and I definately recommend this to speed up your performance.

You will want to take some steps before doing this though.

1) Run firmware updates from the Firmware CD that is Link'd above.
2) Install Proliant Support Pack 7.4 for Windows 2000:
http://h18007.www1.hp.com/support/files/server/us/download/22870.html
3) ***GET A KNOWN GOOD BACKUP***
4) The only last thing that I can recommend is to run the Array Diagnostics off Smartstart and post the results file here after running firmware updates so that we can check to make sure there are no errors on any of your drives first. If you start a migration when there are errors on the drives the migration may fail. Your system does not always warn you of potential errors on the drives and would be a good safety measure.

This is not a fast procedure by any means, but it can be done online and should not cause that much of a performance hit on the server while it is running.

If you would like documentation on why you should switch to 64k stripe size, read this PDF on page 2, was all I could find for now:

http://h200005.www2.hp.com/bc/docs/support/SupportManual/c00366606/c00366606.pdf

Now, as for your BBWC, if you allready have 50/50 for read/write you dont have to enable write caching as it is allrady doing it at the hardware level, but it would not hurt to enable it in software side to see if it helps at all for testing purposes.

[Igor Karasik]

If you have battery pack you can enable write cache, it is safe.
Regarding stripe size:
there is no common rule.
It depends what number of disks you have in RAID-5, if your application write or read
intensive,....
Generally speaking if you have application with many small files stripe size 16K maybe better for your vs stripe size 64K.

[Ryan Goff]

Sorry I forgot to add in steps on how to migrate.

With the array configuration utility open, click the logical drive you want to change, then select the option on the right to migrate raid/stripe. From there you can modify the stripe size to 64k and apply that and save changes to start the process.

You can also get a progress bar by going to the properties of that logical drive to see how far along the process has gone once you save changes.