topic Re: EVA 4400 parity groups in Disk Enclosures

EVA 4400 parity groups

inex — Thu, 06 Jan 2011 16:22:32 GMT

Hi

We have an EVA4400 with 60 disk drives. Does anyone know how data is protected with parity groups among the drives?

-inex

Re: EVA 4400 parity groups

Ali — Thu, 10 Nov 2011 21:51:19 GMT

Hi Inex,

that depends on the raid level that you have configured on this BOX

Check this if u find some info here.
http://h30499.www3.hp.com/t5/Storage-Area-Networks-SAN/EVA4400-performance-documentation/m-p/4712341#M46805

else provide your raid configuration so that we can advice you.

thanks,
Aftab

Re: EVA 4400 parity groups

Johan Guldmyr — Thu, 10 Nov 2011 21:51:42 GMT

Hey,

The subgrouping of disk drives in an EVA is called "RSS" - this is a feature that happens in the background and you have no direct control of it.

Read up on "RSS" - redundant storage set. That is how the EVA is grouping the disks internally.
HP recommends having the amount of disks divisible by 8 for best practices.

This link will give you some more information as well:

http://h30499.www3.hp.com/t5/Disk-Array/EVA-RSS-calculation/m-p/4665686#M35544

Basically if you have one disk group of the 60 disks and you have a vraid5 disk in there. Then you can lose one disk in each RSS before the vraid5 is gone.

If you have a vraid1 in there you can if you are lucky/unlucky lose half of the disks.

Re: EVA 4400 parity groups

inex — Thu, 06 Jan 2011 19:21:08 GMT

How can I see how many rss groups I have among those 60 drives?

-inex

Re: EVA 4400 parity groups

Johan Guldmyr — Thu, 06 Jan 2011 19:55:03 GMT

If you capture a "controller configuration dump" you can see it in there.

Capture it by going to server options -> capture system information -> select "controller configuration dump".

It's in .xml format so it's a little hard to read but it is in there somewhere :)

It might be possible to get it via SSSU but I don't know how. HP took it away from CV because people asked too much about it :)

Optimal for you would be something like this: 8+8+8+8+8+8+6+6

But it depends in what order you put them in etc.

Re: EVA 4400 parity groups

hvhari — Fri, 07 Jan 2011 05:40:58 GMT

These RSS sets are dynamic and can change based on events in the eva (eg. a disk failure or addition of disks etc.). This is totally managed EVA internally and user has no control over it.