EVA 4000 - Disk Drive failure protection

[John Maxner]

Hi, I"ve got my new EVA 4000 all set up, everything looks good - but I'm having trouble understanding the "Disk Drive failure protection" setting on my disk group. Right now it's none. I've read conficting statements on whether this actually affects my protection, or just the amount of time required to rebuild after a disk failure, so....
1.) does anyone know the correct answer to this?
2.) Can I change this setting safely on the fly, and if so, is there any estimate of performance hit for how long?
3.) Has anyone seen a doc that goes a little more in depth than the EVA and CV userguides. Thanks John

[Tom O'Toole · Accepted solution]

1) It does not direct affect 'protection level' in the sense that you could survive more simultaneous drive failures. All it does is remove some space seen by the general storage pool so that you can't use up space that the eva would need to reconstruct full redundnacy after a failure - that is, rebuild mirror/parity data.

2) yes you can change it, and there is no performance hit,but there is loss of max. usable capacity (see 1)).

3) read the best practices paper. Unfortunately, the basic doc. is pretty 'shallow' and other docs are scattered and hard to find.

[Sheriff Andy]

In our environment we have it set to 1 disk failure.

I have been told by our Hardware Engineer that in all reality we can have 3 disks fail in a disk group. This is with the 1 disk failure protection.

There will be a leveling process if you change the the protection level, but I am sure that no one in your environment will no otherwise. That is unless you do a lot of cloning.

Andy

[John Maxner]

Thanks, I'm going to change the protection level to 1. John

[John Maxner]

Thanks, John