How to estimate the capacity needed of Disk Array for 100TB data ?

[MA Qiang]

I should consider RAID5、Hotspare Disk and so on.

How to choice the factor to caculte the capacity needed?

Thanks.

[Uwe Zessin]

It depends on the storage array how it implements RAID-5. Some arrays like EVA or XP have a fixed overhead - e.g. the EVA always uses 4D+1P, the XP has two different levels (5D+1P and 7D+1P ??). Some other arrays (HSG, MSA) always use the equivalent capacity of one physical disk drive, so the overhead is not fixed.

[Vincent Fleming]

With XP, you have the choice of 2 different RAID-5's, 3D+1P, and 7D+1P. There is also RAID-6 (6D+2P).

So, for 100TB usable, you would need approxminately 1000 of the 146GB drives. (that's 250 RAID groups - about 750 for data, and 250 for parity) for the 3D+1P, and about 865 drives for 7D+1P. (214 4-drive disk groups [which is 107 7D+1P] - again about 750 drives for data, and 214 for parity).

Note that the drives for XP are always sold in 4-packs.

You will want about 16 spares for 1000 drives.

100TB is a BIG array. An EVA cannot hold that many drives, so if you wish to use EVA, you will need 5 EVA8000's, each with about 215 drives.

Of course, if you use larger drives (such as 300GB drives), you can save some money, but you have to consider performance.

Goo dluck,

Vince