HPE EVA Storage

EVA 4400 - Adding drives and enclosures best practice.

 
SOLVED
Go to solution
Dja_1
Frequent Advisor

EVA 4400 - Adding drives and enclosures best practice.

We have 2 x 4400s running at production and DR sites. Both are 2C4D with 24 FC and 24 FATA drives distributed vertically through the 4 enclosures. Both at 09522000. 2 DGs only.

We are at maximum capacity now and need to add drives and enclosures starting with FC drives. I have read several forums and articles regarding the ideal of “verticality” when distributing drives through enclosures and also the ideal of adding a minimum of 8 drives to the array. And others regarding adding at enclosures in pairs if possible.

It seems to me that the 3 ideals are not possible to achieve. i.e. add a minimum of 8 disks with 2 enclosures and maintain verticality with the existing distribution of FC and FATA. i.e. currently 24FC on left 24 FATA on right.

Can someone pls steer me in the right direction here?? Many thanks.

4 REPLIES 4
IBaltay
Honored Contributor
Solution

Re: EVA 4400 - Adding drives and enclosures best practice.

Hi,

Why additions of the disks in 8

EVA Disk group (DG) is internaly organized in so called Redundant storage sets (RSS), that by default consist of 8 physical disks. Therefore one of the idea of verticality is to keep each RSS member in the separate disk enclosure.
Then in case of the enclosure failure, the DG continues to work and the production IO is running without the disruption.
the pain is one part of the reality
Dja_1
Frequent Advisor

Re: EVA 4400 - Adding drives and enclosures best practice.

Thanks. I understand the basics of the RSS concepts. It seems odd then the the current M6412 enlosures are 12 Bays not 8 or 16??! I am about to add a single enclosure to each array with 8 FC drives in each. Perhaps I should reconfigure the existing drives (with some additional enclosures) so that I have only 8 in each enclosure. That way if I always add disks in quantity of 8 I will always have enclosure failure protection? Does that make sense?
Víctor Cespón
Honored Contributor

Re: EVA 4400 - Adding drives and enclosures best practice.

The enclosures have 12 slots because that's how many 3.5" disks you can fit in a 2U space.

The idea of 8 enclosures, disks spread on all them in columns, etc intends to provide grater failure protection, but you cannot be sure that the RSSs will be created as you expect. Adding drives to a disk group changes the RSS distribution, and not always in the way you think would be logical.
That can also change next time a disk fails, a RSS can merge with another and then split the resulting RSS.
Dja_1
Frequent Advisor

Re: EVA 4400 - Adding drives and enclosures best practice.

Thanks for the responses.