topic Re: EVA Question in Disk Enclosures

EVA Question

cheesytime — Thu, 16 Jul 2009 12:58:25 GMT

Why would we need to leave a spare disk on our disc enclousure besides for doing leveling when we ungroup one of the disk in the event of a failure?

When does EVA use some free space, do some mainteneance require of free space?

Please advice, this would be for an EVA 4400.

Re: EVA Question

IBaltay — Thu, 16 Jul 2009 13:19:41 GMT

Hi,
on EVA all is virtual on the back-end. There is a so called disk protection level on the Disk group level, which means that you can define the
SINGLE DISK PROTECTION = 2 virtual spare drives
DOUBLE DISK PROTECTION = 4 virtual spare drives

this space is reserved and it is added to the Disk group for the maintenance purposes if needed to add more free space there. Avoid run the production Disk group with NONE DISK PROTECTION...

Re: EVA Question

cheesytime — Thu, 16 Jul 2009 13:40:06 GMT

I knew that, but like, firmware upgrades do need free space? Things like that.

Re: EVA Question

Víctor Cespón — Thu, 16 Jul 2009 13:53:21 GMT

The EVA needs a minimum of 5 GB free on the disk group for leveling and temporary data.

That's why there's a "alam level" and the EVA alerts you when the used space is above 90 or 95%.

By setting "disk failure protection", you reserve the space equivalent to 2 o 4 times the biggest disk on the disk group, to allow the RAID rebuilding to start using that space. This way the rebuild is done withnout having to wait for you to go there and replace the failing disk.

This reserved space cannot be used to create vdisks, snapshots, snapclones, etc and it's not taken into account to calculate the disk group total size.

If a disk fails and there's not enough space left for data + reserved space, then "disk failure protection" is set to "none" and that space appears as available.

Re: EVA Question

Pieter 't Hart — Fri, 17 Jul 2009 05:43:56 GMT

>>>
Why would we need to leave a spare disk on our disc enclousure
<<<

you don't really have a "spare disk"!
the EVA uses all disks.
volumes are spread among all disks in a dskgroup.
the free space also is distributed among all disks.

firmware is not on the disks but in flash memory on the EVA.
so this don't need disk space.

When upgradeing firmware of disks I don't really know if the eva "evacuates" the disk (relocate data to other disks) before upgrading, but i assume it doesn't (looking at how fast that goes).

Re: EVA Question

Mark... — Fri, 17 Jul 2009 15:29:51 GMT

Hi,
Ref Pieter above... no it does not move any vdisks off a disk drive before code loading.

As said above - NO space is required on a disk/vdisk/dg for a code load of the ctrls.
Main thing is to READ the f/w upgrade rel notes, understand them and then verify that everything is correct before proceeding with the code load.

Mark...