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Changing disks on EVA 3000

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Changing disks on EVA 3000

I have an EVA 3000 system fully loaded with 72GB 15K fibre disks. We have recently hit the warning threshhold on capacity, so I investigating possible expansion/upgrade paths. At the moment, it is unlikely we will be able to upgrade to one of the newer EVA systems, so I asked our vendor about the possibility of removing disks from the disk group and replacing them with 144Gb disks one at a time (basically giving enough time for the disk to merge and populate), but I was told that this is a big no no. Normally I have no reason to doubt what my vendor is saying, only I have spoken to two HP engineers that claim this IS possible and relatively straight forward.

We have one default disk group, and have a mix of vraid5 and vraid1 vdisks. These are mirrored to our other EVA via Continuous Access.

Has anyone else been faced with this scenario? I would be interested to hear others opinions and experiences.
6 REPLIES
Ivan Ferreira
Honored Contributor

Re: Changing disks on EVA 3000

We had the same situation, but our HP consultant told us that is a viable solution. We had two choises, upgrade the current 72 GB disks to 146 GB disks by replacing one by one, or adding another disk enclosure. Finally, adding a new disk enclosure resulted less expensive than replacing the current disks, so we opted by that option.

Anyway, what you want to do can be done, but you should be carefull. If your disk group does not have enough disk space, as you said, there may be a problem.

If you remove a 72 GB disk and add a 146 GB disk, and your protection is single (or double) the disk group will substract the space of 146x2 for protection (or 146x4 if double), so this could be a problem, because replacing a single disk will cause that your available space will decrease instead of increase. If you replace two disks at the same time, this problem can be avoided, but your disk group must have enough disk space to acomodate the removing to two disks at the same time. After this, you can replace disk one by one.

Another thing to consider is that ungoupping a disk can take a log time (one day), so, with a fully populated EVA, it can take one month to replace all disks.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Uwe Zessin
Honored Contributor

Re: Changing disks on EVA 3000

Well, you can always set the so-called 'protection level' to "none". It is only a space reservation after all and in the event of a disk failure, the EVA will be able to rebuild as long as there is enough free space in the disk group.

In fact: the EVA will always attempt to take blocks from the "spare space" (=free blocks for virtual disks and rebuild) instead of the "protection space" (blocks reserved for rebuild).

But Ivan is right: it can take a very long time to replace the disks and some internal data structures might get messed up which can cause paired disks (used to store mirror copies) end up in the same disk drive enclosure.
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Re: Changing disks on EVA 3000

Thanks for your comments thus far. When you say "protection space" are you refering to the 10% threshhold?
Ivan Ferreira
Honored Contributor

Re: Changing disks on EVA 3000

No, under the disk group properties, you have and option to select the protection level. This is more or less what before was called "spare disk".
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Ivan Ferreira
Honored Contributor
Solution

Re: Changing disks on EVA 3000

The exact fiel is:

Disk failure protection: Requested Level.

You can disable this protection setting to none, but this will increase the probability of a data loss in case of disk failure, yet more if you will be removing disks from the storage.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?

Re: Changing disks on EVA 3000

Thanks for your comments and pointers. I think what we are going to do is try and free up enough space (ie remove test and low priority systems) so we can ungroup 8 disks and change them for 144s, and probably put these into a new disk group.