topic Adding disk drive on enclosure bay in Disk Enclosures

Adding disk drive on enclosure bay

ANABA — Wed, 23 Feb 2011 15:09:38 GMT

hello

we have an EVA 4000 SAN storage with an disk enclosure (upload with 12 disk drive of 136 GB).
These 12 disk drive are on Default disk group.

We have 2 bay on the enclosure empty.

Could we add two disk drive of 300 GB and add it directly to the default disk group to increase the total capacity ?
Thanks
Regards
M.Anaba

Re: Adding disk drive on enclosure bay

Torsten. — Wed, 23 Feb 2011 15:55:37 GMT

Yes, you can do this as long as the drives are the same type (near-online vs. online).

Due to the different capacity and reserved space (x times the capacity of the largest disk) you may not have so much new space ...) - maybe almost no new space.

Re: Adding disk drive on enclosure bay

ANABA — Wed, 23 Feb 2011 16:02:39 GMT

OK Thanks to your anwser.
But do you mean it's better to add two new drives wih the same capacity (136 GB instead of 300 GB) ?

And the whole added capacity will be add to the Default disk group without any problem on the existing virtual disk ?

Regards
M.Anaba

Re: Adding disk drive on enclosure bay

Torsten. — Wed, 23 Feb 2011 16:07:10 GMT

Existing vdisks will not be affected, but with a setting of "double" the system will reserve 4x the size of the largest disk, now 4x 136GB, then 4x300GB. If you add 2 disks, you may have the same or even less space ...

Re: Adding disk drive on enclosure bay

ANABA — Wed, 23 Feb 2011 16:20:59 GMT

Excuse me but which setting do you mean ?

actually there is :
Total storage space =1366 GB
Storage space used = 1279 GB
Available storage space = 87 GB

If i'll add two drive of 145 GB the available storage space will be less than 87 GB ? That's you mean ?

Regards

Re: Adding disk drive on enclosure bay

Torsten. — Wed, 23 Feb 2011 17:00:01 GMT

Select a disk group and check the "Disk failure protection" level.

Re: Adding disk drive on enclosure bay

ANABA — Wed, 23 Feb 2011 17:19:00 GMT

It's in a single level.

Regards

Re: Adding disk drive on enclosure bay

Torsten. — Wed, 23 Feb 2011 17:35:13 GMT

So it will consume 2x300GB space.

Re: Adding disk drive on enclosure bay

Uwe Zessin — Wed, 23 Feb 2011 17:40:17 GMT

If you add 2 x 300GB, you will win about 272GB (I don't have exact numbers with me - typing this on a smartphone ;-)

This CAN decrease after a disk failure/repair if the EVA fails to go back to the original internal disk group layout. As far as I know, there is no guarantee and the exact behaviour is undocumented

Too bad that even after _that_ many years there is no 'disk trunkate' capability to mimic the behavior of traditional RAID arrays (use capacity of smallest disk drive in group) to make the system more predictable

Re: Adding disk drive on enclosure bay

ANABA — Wed, 23 Feb 2011 17:58:36 GMT

thanks to all.

So il will add 2 drive of 146 GB.

If i understand you well it will be more easier to add them in the existing default disk group which contain already 12 drives of 146 GB capacity.

My available storage will be arround 250 /300 GB right ?

Regards

Re: Adding disk drive on enclosure bay

Steven Clementi — Wed, 23 Feb 2011 18:09:47 GMT

"If i understand you well it will be more easier to add them in the existing default disk group which contain already 12 drives of 146 GB capacity."

This is your ONLY option. You can't do anything else with just 2 disks.

"My available storage will be arround 250 /300 GB right ?"

You will gain the raw space of the 2 new drives. 136*2 = 272 (+ 87 = 359GB (vRAID0)) so yes, between 250 and 300 for vRAID5, less for vRAID1.

If you were to add the 300GB drives... you would recover the current lose of 272GB of protection space, but replace it with 558GB (2*279GB) so it's a wash. Either way, you still end up with the same amount of space (at a higher cost).

The only real upside is... it makes transitioning to all 300GB disks easier in the future.

Steven