topic VA7100 usable disk space after format in Disk Enclosures

VA7100 usable disk space after format

Eric Firkey — Wed, 07 Sep 2005 10:54:21 GMT

Hi,
If I fill a VA7100 with 73gb disk I end up with 1.095 Terabyte of disk. How much of this will be usable after I format the array? Thanks.

Re: VA7100 usable disk space after format

Torsten. — Wed, 07 Sep 2005 11:38:52 GMT

Hi Eric,

it depends!
The capacity is affected by the mode (AutoRAID vs RAID0/1) and the number of configured spare drives. In fact, "spare drives" is reserved space spanned over all disks. Additionally the array is reserving some space for itself. You can check by

# armdsp -a

the section called

"CAPACITY USAGE"

and you will see the amount of allocated space by LUNs and available space for LUNs.
You can see this prior to a format also, if the disks are included yet.

I would expect ~850GB for typical settings.

Please post the result of armdsp -a, I'm interested too.

T.

Re: VA7100 usable disk space after format

Luk Vandenbussche — Thu, 08 Sep 2005 01:10:50 GMT

Eric,

I have a VA7400 with the following settings
AutoRaid and Automatic Hot Spare.
The you have a usable capacity from 66,757 GB for each drive.
I have the following capacity in my redundancy groups
RG1 : 400 GB
RG2 : 400 GB
In your case this must be (when you use autoraid)
RG1 : 534 GB
RG2 : 467 GB

Re: VA7100 usable disk space after format

Peter Mattei — Thu, 08 Sep 2005 08:35:56 GMT

Uups, we are talking about a VA7100 here right?
The VA7100 only has one redundancy group wher all disk belong to. The max is 15 disks.

Using AutoRAID you can get 800GB free space, when you do not define hot spare.
But, do not do that!

If you define a hot spare of 1 you will get 740GB net.
Note: If you fill an array in AutoRAID mode your write performance will decrease dramatically. This is OK for a WEB server but definitely not for a DB server.

To achive best write performance I would set the VA7100 to RAID1 and define 1 spare.
This will give you almost 500GB which you can fully allocate.

Cheers
Peter