topic Re: Adding EVA3000 Disk Groups in MSA Storage

Adding EVA3000 Disk Groups

BR824100 — Wed, 27 Oct 2004 04:47:54 GMT

I have to expand an EVA3000 with two additional disk shelves and was wondering if there is some kind of best practice with regards to the disk group allocation?

The current two disk shelves have 3 large oracle databases and our exchange system sitting on them.

I just wanted to know if it is better to add all the new disks to the single existing disk group to spread the databases over more spindles or create a separate disk group for the new shelves and move two of the oracle databases on to it instead?

Re: Adding EVA3000 Disk Groups

Steven Clementi — Wed, 27 Oct 2004 18:01:27 GMT

HP recommends "one" disk group. There is a document with recommended practices when it comes to the EVA. I need to find the link again.

I would have to say that if you need to give more storage to your existing servers and you want to "expand" their current rives, then you NEED to have the space in the same Disk group.

If you just want to allocate more Virtual disks, then a new disk group might be feasible if your experiencing trouble with the current configuration, but not necessary.

Steven

Re: Adding EVA3000 Disk Groups

Ole Thomsen — Thu, 28 Oct 2004 00:17:11 GMT

Does "one diskgroup" also apply when the new disks are larger/faster than the old ones?

We have two shelves with 76GB/10Krpm in one diskgroup, the next shelf will probably be filled with 146GB or 300GB disks.

Re: Adding EVA3000 Disk Groups

BR824100 — Thu, 28 Oct 2004 03:42:27 GMT

Thanks for your replies.

With regards to the third posting I assume you would need two disk groups otherwise how would the system level the data across different sized disks?

Re: Adding EVA3000 Disk Groups

Steven Clementi — Thu, 28 Oct 2004 06:36:13 GMT

Personally, I like to keep my different size disks together in one group.. That is, a group for 72's a group for 146's, etc.

You can however, mix and match within 1 disk group, but keep in mind a few things...

1. The larger disks will hold more data then the smaller disks (duh, I know). What I mean is, if you write out a 1GB file to a Vdisk that had 4 disks (3 72's and 1 146 (I know, i know, impossible....but this is just an example) ) Each of the 72's would have 200MB each and the 146 would have 400MB.

2. Your protection level is calculated using the LARGEST size drive in the group. If you have 6 72GB and 2 146 in a disk group of 8 disks with double protection, you end up with 146*4 used space for your group protection (144GB raw)

3. I am sure there are other reasons too, but the previous 2 are very important to consider.

Steven

Re: Adding EVA3000 Disk Groups

Uwe Zessin — Thu, 28 Oct 2004 13:07:30 GMT

2): 4*146 = 584, not 144. It leaves you with 140GB of raw capacity for creating vdisks - a good business for your hardware supplier ;-)

Here is the link to:
"HP StorageWorks Enterprise Virtual Array Configuration Best Practices (5982-9140EN, October 2004)"
http://h20000.www2.hp.com/bizsupport/CoreRedirect.jsp?targetPage=http%3A%2F%2Fh200007.www2.hp.com%2Fbc%2Fdocs%2Fsupport%2FSupportManual%2Flpg29448%2Flpg29448.pdf

Very, very interesting reading!

Re: Adding EVA3000 Disk Groups

Steven Clementi — Thu, 28 Oct 2004 13:30:28 GMT

Should have been a bit clearer. the (144GB RAW) was meant to meant what you have @ usable not how much protection space in the example.

SC