Raid Stats!


Javacat

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Anyone got a link for some site that's got stats for different RAID setups with different types of hard drives or experience with them? I'm basically in need of some statistics comparing SAS drives in RAID 5 and SATA drives in RAID 10. I've looked all over, but can't find any sites with a decent amount of information.

The situation is I'm pricing up a file server for an SMB (which means the price needs keeping down) that needs to be as fast as possible, with as high capacity as possible. For the price of 4 SAS drives (that would be run in RAID 5 to maximize the storage, giving me just 900GB of space) I could get 8 SATA drives (that would be run in RAID 10, hopefully giving a very nice performance increase, better fault tolerance and 2TB of storage) and still save money.


For anyone interested, I'm looking at the HP DL180 G5 using HPs hot-swappable hard drives, which would be running Windows Server 2003 Standard.
 
I don't think you'll find much material on that, because it's very much down to drives, controllers, firmware, setup etc. To be honest, SAS is incredibly expensive and you're paying for reliability, warranty, etc. SATA is a consumer technology, where you're paying for a bit of hard drive space. You can use SATA in RAID configurations in order to account for this, or you can use SAS in lesser configurations. It's all pretty much a toss-up between the two. Modern hard-drives are fast enough and big enough to make most issues moot. The speed increase you'll see from RAID10 is probably going to be lost in the void, especially if the server isn't really being pushed to the limits (as most office/business servers aren't).

For instance, I build/run servers for schools and even with 450 users, we don't see any significant disk activity that RAID10 would ever speed up. So we run RAID5 over SAS drives. In another school just last year, I've had servers running off Fast SCSI RAID's that were able to serve 1000 users on 400 clients with barely a struggle. It weren't fast but a 50-second login is hardly different to a 20-second one when you are talking about ordinary users.

It's up to you, you can get a lot of value for money with large numbers of cheap drives and exotic RAID configs (RAID5+0 etc. http://www.pcguide.com/ref/hdd/perf/raid/l...tLevel05-c.html is a good site to get a quick rundown on them) on a couple of good controllers. The idea of RAID is to make inexpensive disks (that's what the "ID" stands for) more reliable. The performance increases are negligible unless you're running things to the absolute limit, and then you're better off just buying better disks in the first place.

Just a word of warning - DO NOT FORGET TO INCLUDE TAPE BACKUP. RAID is not backup. I'd rather have a single drive hanging off an IDE connector with additional tape backup than all the RAID's in the world without tape backup.

P.S. Oh, and in case you're wondering, a school setup is actually more critical and more performance-intensive than a business set up of a similar size. Modern schools cannot open without the computers working - registration, timetabling, contacting parents, arranging catering, paying suppliers/staff, truant-detection systems, CCTV, access control, all run off the system, not to mention actual lessons (and all subjects are required to include some ICT now). Additionally, the environment is stressful, time is critical (30-second boot-ups, 20-second log-ons in the good schools), users are mostly non-technical (2Gb Powerpoints in their home directories etc.) and logins are in batches - most business networks are stressed at 9am as people come in and then not again until 5pm when everyone logs off. School networks are taking batches of dozens of simultaneous logins at 30-minute intervals. All with huge profiles, masses of software, stressed teachers waiting for it, and all running off a tiny amount of servers (most schools have 2 if you're lucky...).
 
Thanks for the info. When thinking of RAID I think of ID meaning "Independent Disks", which is apparently a more modern meaning for the acronym. Reading it as "Inexpensive Disks" now has made up me mind for me. SATA it is :p

I gave that site a read and I think that I will stick with RAID 10 for the recommendations for now, although will be considering other RAID setups up until whatever point the system is implemented.

Thanks for your input on this!


PS, The backups are already covered, although I'll be looking into expanding the backup system once the additional space of the new server starts to get abused. I suspect they wouldn't be too pleased with the price of the system if an Ultrium 4 drive was included with it at the same time :ph34r:


BTW, I have no doubt about a schools network being performance intensive. Thats one system I wouldn't fancy being the admin of. Anything with kiddies is a nono ;)
 
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