RSS sets

[Brian Kerr_1]

We have just upgraded from a 2C4D EVA500 with 24 disks to a 2C8D with 48 disks physically arranged as 6 per tray.

The main reason for this move was to, we believed, obtain best protection from a disk tray failure by having 6 RSS sets striped across the 8 trays, 1 member per tray.

In practice we now have a Mirrored RSS state with 7 RSS Sets - 3x8 disks & 4x6 disks. (Map attached as JPG.)

Is there a straightforward way of persuading the EVA to change this configuration?

Thanks,

Brian Kerr

[Urban Petry]

What vRaid levels are you using? If you _only_ have vRaid1 VDisks then you can afford a loss of a disk shelf now (assuming you have a mirrored RSS state as you said). If you have vRaid5 VDisks as well then you need to get to a Parity RSS state. I don't know of any way to explicitely tell the EVA what to do with its RSS (after all it's a virtual array), but you could try the following:
- although your current RSS configuration is ok I would probably first try to get RSS sets with 8 disks each (the "preferred" size); I hope you have enough free space to temporarily ungroup 8 disks which hopefully forces the EVA to create 5 RSS sets with 8 disks each (haven't tried this, I hope it's not keeping the 4x6 disks and dumps 1x8 ...)
- then you have to manually reorder the disks so that no two disks of the same RSS set reside on the same disk shelf. This unfortunately means a downtime if you want to be on the safe side (at least according to some statements I heard from HP you can swap disks online when you stay within the "Disk Replacement Delay", but I wouldn't rely on that as I have not confirmed this myself :)

Not a quick solution I must admit ...

[Brian Kerr_1]

We do have VRaid5 discs and it is the parity RSS state that I'm seeking. Having been told everywhere we looked that the EVA would put itself in to the 'preferred' 8 disk per RSS set format it it could that's what I hoped would happen when we recently added 24 disks. A downtime would be my last resort as a main selling point for getting the SAN was it's availability! We have got a fair amount of space just now though so I could try the disk ungrouping route.

Thanks.

[Urban Petry]

Just remember that the ungrouping step is only the first one. Maybe you're lucky and you don't need reordering but I doubt it.

Do you have EVE heartbeat mails configured now? If this is the case you can easily find out at the bottom which RSS sets are causing the "only Mirrored" state. Maybe you can ungroup some of these disks to sligthly force the EVA into the right direction. But whether this leads to nicely aligned 8-disk RSS sets is another story ...