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Why is EVA leveling twice?

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Frequent Advisor

Why is EVA leveling twice?

Hi all,

We recently had a disk failure in our EVA4100.

This was the sequence of events:

A physical disk drive has been rendered inoperable.

A physical disk drive has disappeared.

A member management operation has started due to the appearance or disappearance of a physical disk drive.

At his point the disk has become 'unidentifiable'
The Diskgroup status changes to 'Leveling'
After 8 hours Leveling reaches 100%
But Leveling then starts all over again:

Leveling of capacity in a Disk Group has started.

There are a couple of things I'd like to ask:
1) Why does the EVA perform the second leveling phase?
2) At what point is it safe to replace the disk (not necessarily add it to the diskgroup, but just replace it)?

Valued Contributor

Re: Why is EVA leveling twice?

Could be the prob with the disk itself,if the disk is not dead try to ungroup it and replace it .... you can add new disk at any point of time.. it wont be any problem.
Uwe Zessin
Honored Contributor

Re: Why is EVA leveling twice?

> 1) Why does the EVA perform the second leveling phase?

The EVA sometimes does, erm, undocumented things.

> 2) At what point is it safe to replace the disk

According to the "configuration best practices white paper" (4AA0-2787ENW) you should wait for the data reconstruction (= VRAID rebuild) to finish, before you start with removing the old disk. You have to check the controller event log to find out :-(

The data leveling starts after the reconstruct, but you don't have to wait for leveling to finish.
Frequent Advisor

Re: Why is EVA leveling twice?

thanks for your answers.

The weird thing is, the first Leveling took 8 hours, now the second one is at 2% after 3,5 hours.

We also have twice as high as normal iowaits on the servers with EVA Vdisks attached.

The leveling seems to take away IO performance, while not making any substantial progress itself.

Btw, our software version is SR1142xc3p-6200

Frequent Advisor

Re: Why is EVA leveling twice?

Does event "A member management operation has started..."
indicate the start of the reconstruction?

If so, then that seems to have finished after 8 hours, indicated by events:
"A member management operation has finished"
"A Volume was removed from a LDAD"
"A Disk Group has transitioned to the NORMAL state"

I'm not sure why EVA started a leveling process right after that, when we haven't replaced or added the new disk to the diskgroup yet.

Thanks for the whitepaper link.
Mark Poeschl_2
Honored Contributor

Re: Why is EVA leveling twice?

I've seen something similar on our EVAs in the past. It seems that when a disk fails hard there are two separate "leveling" operations that have to take place. I think the first is a migration or rebuild of the data that was on the lost drive and the second and separate operation is a leveling of the data across the new set of RSS's that remain after the failed drive is taken out of the picture. It's never been clear to me why this can't all be completed in one operation, but as Uwe says the EVA's internals are sometimes a bit mysterious.