topic Re: VA7100 disk capacity in Disk Enclosures

VA7100 disk capacity

Edward Carey — Wed, 19 Sep 2001 19:03:28 GMT

Did anybody know how to calculate the approximate usable disk capacity for VA7100 in AutoRAID mode...???

Re: VA7100 disk capacity

Enes Dizdarevic — Thu, 20 Sep 2001 07:03:13 GMT

Maximum disk capacity in autoraid mode is achieved when all data are on raid5dp. Raid5dp is described on page 37 in Users Guide. Raid5dp uses capacity od 2 disks to store parity data (distributed evenly on all disks). So maximum usable capacity is (if all disks are equal in capacity) (number of disks -2)*capacity of disk. You have to deduct capacity dedicated to "image disks" from this. Image disk are used for saving maps from cache. It is not clearly stated im manual if space for image disks is equal to maximum possible cache size or current size. I think it is maximum cache size (1GB) in order to avoid rebuild of image disk arrea when cache capacity is upgraded. This space is mirrored on two disks.
Minimum capacity is achieved when all data are in raid 1/0 so it is half of capacity of all disks.
And if you have hot spare disks you have to exclude them from calculation of usable capacity.
Hoppe this helps.

Re: VA7100 disk capacity

Edward Carey — Mon, 01 Oct 2001 14:36:45 GMT

Well...
This is what I got from another HP tech guy...

Current 10x18G will have 108GB with HotSpare, and 126GB without.

15x18GB will have 198GB with HS and 216GB without HS...

In summary, it took 4 drives for AutoRAID mode with HotSpare and 3 drives without HotSpare

Re: VA7100 disk capacity

Enes Dizdarevic — Tue, 02 Oct 2001 07:09:22 GMT

Actually things are more complicated than that (eventhough this can be a good approximation). There are for modes for hot spare: None, Automatic, LargestDisk and LargestTwoDisks, and you may have different disks size in your array. Information you got are based on equal disk capacity and LargestDisk or LargestTwoDisks hot spare configuration. Next complication is capacity for image disks and the fact that in autoraid mode some capacity is allways in raid 1/0. HP has capacity planning tools which are for HP and channel partner use only. If you give me exact configuration of you array (number of disks and hot spare mode) I can calculate usable capacity and post a result.

Re: VA7100 disk capacity

Carlos Sotelo Ibarra_1 — Tue, 02 Oct 2001 16:36:27 GMT

As a case example: I have 6 36Gb hard disks, one as hot spare... and only get 63Gb allocable space. I assume that this capacity is in Raid 1/0 mode, how and when does that change to Raid 5dp? And when it does, will I have to rebuild the file system in order to take advantage of the extra space?

Re: VA7100 disk capacity

Edward Carey — Tue, 02 Oct 2001 17:59:33 GMT

What we have currently on our VA7100 is 10x18GB disks which give us 120GB usable capacity without Hotspare. If I set Hotspare to Automatic, it will have 102GB (120GB-18GB).

Re: VA7100 disk capacity

Enes Dizdarevic — Wed, 03 Oct 2001 06:03:32 GMT

HP table gives this result for 10 18GB disks for autoraid mode:
1) no active hot spare = 128,9 GB
2) capacity of one disk hot spare = 112,4 GB
3) capacity of two disks hot spare = 96,0 GB

Re: VA7100 disk capacity

Carlos Sotelo Ibarra_1 — Sat, 10 Nov 2001 20:12:45 GMT

As stated before, I had 6 36GB disks, when hotspare was enabled, it took over 68 GB of space.

I finally had to do without the hotspare functionality in order to get the space.

When AutoRAID is enabled - and that required me to get to the virtual front panel through the rs-232 port in the back of the unit - I got some 120 GB of allocable space and about 80 GB of redundancy. That's about what I expected from the specs and coincides roughly with the formula stated elsewhere.