Diskarray/Raid : fibre channel or SCSI ?

[Lothar Krueler]

Hi there,
i'm thinking about replacing 3 Autoraid 12H for better disk-performance and eventually replacing the two via "C875 Fast Wide Differential" interfaces connected L-2000 Servers(each 2 CPUs and 2GB Ram, MC-ServiceGuard). Therefore an upgrade to 4 CPUs and 4GB Ram each server probably might be enough. The servers don't have FC-interfaces.
I've got an offer about an EVA3000 to be connected via 2GBit FC-Interfaces and a FC-switch. What disk-performance can i really exspect in relation to that, what i have ?
Are there other raids to be connected via newest SCSI technology, which are less expensive and fast enough ?

I'll go to holiday for the next 4 weeks, so i cannot promise reading responses and assigning points until i'll be back again.

Thanks in advance
Lothar

P.S. This thread has been moved from General to Disk Array. - Hp Forum Moderator

[Brian M Rawlings · Accepted solution]

Lothar:

One important thing you haven't mentioned is how much disk space you need. This actually can bear on performance, as you may have seen with your 12H arrays. If you put the minimum number of drives (four) into a 12H, you will have much worse performance for any given LUN than if you fill it with 12 drives.

Likewise, with the EVA3000, if you put in the minimum number of drives (eight), you won't be able to push a lot of performance through the array. It will be better than your 12H arrays, to be sure, but nothing like you could be getting.

The related factor is, what drive size do you use? with 8 146GB drives, you can have nearly 1TB of storage, but you will be performance constrained compared to the array with 1TB of 36GB drives (32-36 drives). And of course the stressor there is cost, because the array is cheapest with big drives, and more expensive as you add performance through lots of smaller drives.

Regarding your question about SCSI vs. Fibre Channel, what you will find is that there are some no-name SCSI arrays out there that you could use, which would be faster than your current 12H units, but they would all be using UltraSCSI (LVD), not the older HVD/FWD that you currently have. Your current HVD (20MB/s max, 15MB/s sustained) is a real performance limiter, you'll have to move up to Ultra160 or Ultra320 or Fibre Channel any way you go.

I would avoid the SCSI solutions, if I were you, for two reasons. One is overall performance. Although they'll be faster than the 12H units, they'll be slower than real FC arrays, in just about every respect. The second is supportability. It is normally good to stick to one vendor, if they have a competitive offering. You have HP servers, and presumably an HP maintenance contract. An HP array makes great sense, so that if anything -- ANYTHING -- goes wrong, one vendor is in there, with responsibility for all the gear. It will get fixed, no finger-pointing, no hassles (well... reduced hassles).

EVA needs 20-30 drives to really hit its stride, performance-wise. When you set it up right, it can be very fast, and will no doubt do the job for you. If you just stick the minimim eight drives in it, you will probably be disappointed (true for most arrays, actually). If 20 drives doesn't make sense economically, the more the better, and try to avoid the minimum if you can.

Lastly, modern arrays (FC or SCSI) have lots of neat features that you can use, like snapshots for backups, etc. These end up requiring more space, but can make sense economically if they can reduce your backup library size or tape count. And then you end up with more drives, and... hey, look, better performance. Cool

Take Care,

--bmr

[Lothar Krueler]

Hi Brian,

thanks for your response. Because of my bad english i've to think about. But i'm sure it it will help so i can close this thread now.

Thanks again
Lothar