Disk Arrays
cancel
Showing results for 
Search instead for 
Did you mean: 

Usable capacity on EVA5000

Usable capacity on EVA5000

Can anybody out there explain to me how I calculate server usable capacity (Raid-5) on an EVA 5000.

Situation is:

32* 73 GB drives
2 Vraid pools
Highest level Hot Sparing

If it makes any difference, snap vill be used in both pools.

Thanks in advance
6 REPLIES
Joshua Scott
Honored Contributor

Re: Usable capacity on EVA5000

The way RAID-5 works is that there's a data stripe that goes across all but one of the disks and a parity check on the other disk. So the way to calculate it is:

([number of drives in RAID group] -1) * [size of drives] - ([number of drives used for hot-spares] * [size of drives] = [capacity of RAID group]

HTH

-Josh
What are the chances...
Mike Naime
Honored Contributor

Re: Usable capacity on EVA5000

Plus, you have a Occupancy Level that you do not want to go over.Compaq/HP recommends that you leave at least 10% of the usable total storage space as free space. (No more than 90% occupancy). This allows the EVA to re-shuffle the data when you do have a drive failure.
VMS SAN mechanic
Claudiu Schmidt
Valued Contributor

Re: Usable capacity on EVA5000

Hi,

we have a EVA installed with 64*73GB disks, and we have a usable space of 3.2 TB in Raid 5. We have a single disk failure protection. So here is how I calculate usable space. if you have 32 disks, and 2 diskgroups with double protection, you loose 8 disks, 4 on every diskgroup. the raid 5 is a virtual one, but you loose around 20-25% for parrity. so in you' re case, you will probably have a usable space of ((32-8)*73GB)*75% = 1.3 TB

Rgds,

Re: Usable capacity on EVA5000

Thanks a lot Claudiu.


This seems to match my reality qiute well.

Do you, by any chance, know if any official formula or tool exists to do this calculation for various scenarioes ??

rgds
Claudiu Schmidt
Valued Contributor

Re: Usable capacity on EVA5000

Hi,

i know there is a tools to calculate the usable space, but i never had it. you should ask a sales guy from HP , because they work a lot with this tool.

Rgds,

Claudiu

Re: Usable capacity on EVA5000

Downloaded EVA calculator from this web site