Exchanging 146Gb drives for 300Gb in a Disk Group

[Del_3]

We need to swap the entire disk group of 146Gb drives for 300Gb FC drives. Is there any reason we cant do this by grouping eight 300Gb to the "146Gb" disk group and one by one removing the 146Gb drives, allowing leveling between each removal? We will have a mixed DG for a time.

Thanks in advance.

[Steven Clementi]

Del:


You can easily add the 300GB disks to the existing DG. Doing so will increase your reserved storage based on your protection level...

PL none = 0GB becomes 0GB
PL Single = 2x146GB becomes 2x300GB
PL Double = 4x146GB becomes 4x300GB.

Adding the 8 disks at once will satisfy the need for more available storage to cover your protection level. It would also level out so you'd have to wait for the first leveling before doing the removals.

Then, you can remove them one at a time allowing them the level. I think you can do multiple remove, but have never done it beore so not sure if it would work. WOuld be great though to tell it one thing to do instead of 8.


Steven

[Del_3]

So if I add one 300 Gb drive I will actually lose raw space.

What I wanted was confirmation that we can mix disk sizes in a DG and do this a drive at a time (after the first eight). I.E. add a 300, level, remove a 146, level etc.

[Uwe Zessin]

Yes, you can mix, but you might not get the expected result ;-)

[Del_3]

Uwe you must clarify. What does your statement mean?

[Steven Clementi]

Del:

Yes, if you add a 300GB disk AND your protection level is single or double, you will lose raw space because the the protection level will be based on 300GB (x2 or x4) instead of 146GB.

Yes, you can mix disks. It is best to add 8 disks at a time though, or a multiple of 8 (See your other posting). How many 146GB disks do you have?

You can also drop your protection level for the process, than bump it up again after your done or have enough to cover, so you don't lose the extra space right off.


Steven

[Del_3]

I have 4 shelves with 11 slots free now. I can add eight disks initially with a sparring level of 2 or 0. But then I will need to add three drives and then begin to swap one for one. Can I do this with out mucking up my RSS config or creating a dangerous environment?

My goal is to swap the entire array with 300Gb drives.

[Uwe Zessin]

Well, due to enhancing the disk group with larger disk drives, the EVA will configure more protection space, as Steven has already explained.

If you add an odd number of disk drives to a disk group with an even number of disk drives, you will not be able to use the capacity of the last disk drive for VRAID-1 virtual disks. So you are about 280 SWGB short on space.

And depending on _how_ you swap the disks, you might end up in bad RSS configurations, yes.

[Del_3]

Alright then what if I can ungroup two 146Gbs and then add two 300's after the initial eight swapped? Will this avoid the mess?

Thanks again.

[Uwe Zessin]

No mere mortal knows, because the algorithms are not published and (can) change over time. The only chance for us that I can see is to just do the operation and then verify the RSS layout.