topic Re: eva + lvm striping in Disk Enclosures

eva + lvm striping

ChewSP — Thu, 08 Sep 2005 04:57:05 GMT

i would just like to know if there is any benefit in implementing this:

eva with a few virtual disk and then lvm stripe them into a single vg.

will there be performance improvement? is it a best practice?

Re: eva + lvm striping

Leif Halvarsson_2 — Thu, 08 Sep 2005 04:59:55 GMT

Hi,
No, it will not give any performance benefit nor be any "best practice".

You can activate the full performance of the EVA, using one single LUN.

Re: eva + lvm striping

Markus_10 — Thu, 08 Sep 2005 06:00:12 GMT

Be aware of this:

When presenting only one vdsik to a HP-UX System you have to change the kernel paramater:
scsi_max_depth - standard is 8

Some of our customers had very poor performance, aftre raising this paramter everything works fine.

This parameter must be set in VMware ESX environments too, when using only one LUN.

Markus

Re: eva + lvm striping

Peter Mattei — Thu, 08 Sep 2005 08:48:37 GMT

Look at this:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg35039

And Leif: In order to achieve full performance of an EVA you need to allocate at least 2 LUNs, 1 on each controller!

Cheers
Peter

Re: eva + lvm striping

Sameer_Nirmal — Thu, 08 Sep 2005 17:18:17 GMT

I don't think its a good idea. There would be little or no performance gain with LVM striping.

As you might be aware , EVA does the striping of its own. So there would be double striping .If you enable LVM striping , there are overheads involved as well. From OS perception , there would be slight LVM striping overhead . From EVA perception, it is little more overhead to it as you are making him work more. Although EVA is powerful enough to handle the overhead, it is always good to allow him to work of its own.

To get maximum throuput from EVA you can have 1 disk group and Vdisks/LUNs equally distributed/balanced on the two controllers.

Although it is not mentioned in HP's best practices about LVM striping, I would say it is not required.

Re: eva + lvm striping

Mike Reznak — Fri, 09 Sep 2005 07:04:07 GMT

If you have free resources, then test the different configurations, to the real impact.
Mike

Re: eva + lvm striping

Mike Reznak — Fri, 09 Sep 2005 07:05:17 GMT

Sorry. Once more the whole sentence...
If you have free resources, then test the different configurations, to see the real impact.
Mike