EVA5000 Adding diff disk sizes to disk group

[gavin.scottza.didata.co]

We have a EVA5000 SAN. We have a disk group containing 72GB Hard drives. We would like to increase the capacity of this disk group. If we add 146GB hard drives to this disk group, will all the 146GB available space per disk be utilized, or will only 72GB be used per disk?

[Uwe Zessin]

All space can be utilized. Of course, you will have more data on 146GB spindles than 72GBs.

And remember that the protection capacity is calculated by using the size of the largest disk in the group. Single protection will reserve 2x146GB.

[gavin.scottza.didata.co]

So to confirm, so that I understand how the HSV controllers manages to maintain data protection levels whilst utilizing all available disk space (irrespective of disk size)

Once the new 146GB disks have been added to the disk group, the levelling process will spread the data evenly amongst all the members in the disk group. Therefore it will handle the fact that the 72GB disks will get full before the 146GB disks and if I understand you correctly; continue with the even spread of data amongst the remaining 146GB hard drives, untill they become full?

[Uwe Zessin · Accepted solution]

Sorry, my parser is a bit weak today, so I am not sure I really understand what you are saying. Let me quote the User Guide:

""The EVA will attempt to ensure that the amount on each physical disk drive is proportional to that drive's contribution to the overall capacity. This means that larger drives will have more data on them than smaller drives. As an example, a 72GB disk will have twice as much user data on it as a 36 GB drive.""

[Orrin]

Hi Gavin,

Uwe is right as always. I think you missed a very important point he mentioned in his first answer. It's to do with sparing.

e.g If you have 7* 72GB in your diskgroup and have single sparing ( bare minimum )
the HSV will have reserved 2 disk of the maximum size. i.e, the amount of space available to you is 5*72GB.
Now if you add one disk of 146 Gb , then the HSV with single sparing reserves 2*146 GB, so the amount of space available to you is still 5*72GB.

For double sparing, it is four disk.

Hope this helps...

Regards,
orrin.

[Iyad Abou Hawili]

If I have a full enclosure with 72GB hard disks in one Disk Group and I want to change these 72GB harddisks to 146GB hard disks. Is it possible to replace these 72GB hard disks one at a time by ungrouping a 72GB disk, locating that disk, physically removing that disk, then adding a 146GB disk then adding it to the disk group, wait for the levelling to finish then repeat the process again with all the 72GB disks.

Baring in mind that I have enough space so I will not be short of space if I ungrouped one ore more of the 72GB disks.

Does this sound a good procedure to follow? any other recomendations?

Iyad

[Uwe Zessin]

I have responded in your own thread:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=997171