Which RAID

[Techie101]

Hi

 

Quick question a primary school has a server with 4 300gb sas drives. Now I know it is normal to go with RAID 5 but the school wants performace over anything. So I am tempted to go with RAID 0 as both read and write speeds would be good, unlike RAID 5 where writes can be slow.

 

I know if a drive in RAID 0 fails your stuffed but the school is backing up daily using Acronis backup software which takes an image of the server onto an external network drive. So if a drive did fail it just needs to be replaced and the server restored from the backup image. RAID 0 will give them the perfomance they want so what do you all think?

 

cheers

[SYNACK]

I had the same concerns at one of my schools and went for RAID1+0 which gives you the speed and also good redundancy. I would not forgo the redundancy offered by RAID>0 as it does not matter how fast it goes if one drive cooks and everyone has to wait a day or even a couple of hours while you rebuild it. Also if it goes at the end of the day before the backup has run thats a whole day worth of work possibly gone, its just not worth the risk in my opinion.

[3s-gtech]

Go with redundancy first, and build speed in. Do they really need enterprise-class speed? Could you get quicker spindle disks in the future? Or even SSDs? I would never use RAID0 in a server that would matter if it went down (which is surely 99% of them).

[tmcd35]

Agree with Synack, RAID 1+0 would be a more sensible option. But there is also the question of space availble - RAID-0 = no redundancy, v.fast speed, 1.2Tb. RAID-10 = 2 drive (potentially) redundancy, fast speed, 600Gb. RAID-5 = 1 drive redundancy, slow speed, 900Gb.

 

SAS drives are pretty fast at the best of times and for *most* people RAID-5 is more than quick enough, unless you're running a demanding SQL database? And that's the question really - how meny users, what type of data? Also how fast are the drives 10k, 15k? Cache sizes?

 

I've got a feeling that once you've answered those questions, considering 900Gb vs 600Gb, and 1 drive redundance vs no redundancy, we'd be recommending sticking with tried and tested RAID-5.

Edited May 28, 2010 by tmcd35
typing with a lisfp :p

[sparkeh]

Personally I would go with RAID5, for me the redundancy is the important thing and would anyone really notice the write speed?

[pete]

RAID10 if you need performance. RAID0 is bloody irresponsible if it holds any data you care about that isn't getting immediately dumped somewhere else (i.e D2D2T). That goes double for a primary with (I assume) limited technician time and lots of eggs in the same basket.

[adampat84]

RAID0 is bloody irresponsible if it holds any data you care about

 

I agree with the above.. i'd never dream of using RAID 0 in a server..

 

"if you play with fire; you get burnt"

 

Its not worth the risk, no matter how fast you make it users will always say it's too slow..

[Guest TheLibrarian]

IMO the OP should give the HT the facts, pro's and con's with a goodly piece of advice of what the OP thinks would be the best choice then let the HT make an informed decision with guidance.

 

If the HT will live with losing up to a day's work and a day's down time for recovery in the pursuit of speed, then that is the HT's perogative.

 

I believe in giving the 'customer' the choice as long as they are armed with the information to make their choice.

 

 

I should also add, if it was left to me as a techie, I'd go with RAID 5 because RAID 1+0 is not worth the performance gain.

Edited May 28, 2010 by TheLibrarian
Forgot to add my preference.

[azrael78]

Here we use RAID-5 for pretty much everything with a few exceptions, where we use RAID-1+0.

 

My personal choice would be RAID-1+0.

 

If you are doing a daily backup that will give you an additional layer of protection against serious data loss, but don't rely soley on your backup, if you have the capacity (and cash) to add hardware redundancy then do so.

 

The RAID 1 (Mirror) will give you extra redundancy as well. Not that I'm slating RAID-5 or 10 but RAID-1+0 sounds like it fits the schools' primary 'we want performance' requirement as well as giving you redundancy as well.

 

Az

[Techie101]

IMO the OP should give the HT the facts, pro's and con's with a goodly piece of advice of what the OP thinks would be the best choice then let the HT make an informed decision with guidance.

 

If the HT will live with losing up to a day's work and a day's down time for recovery in the pursuit of speed, then that is the HT's perogative.

 

I believe in giving the 'customer' the choice as long as they are armed with the information to make their choice.

 

 

I should also add, if it was left to me as a techie, I'd go with RAID 5 because RAID 1+0 is not worth the performance gain.

 

Thats what I did, and he went with RAID 0. The server does not hold any critical data, each teacher is resposible to keeping all critical data backed up via memory sticks etc, the school also backs up daily onto several network drives. And if the server did go down the head is happy that it may be down for a few days in order to order parts and reimage the server, so in other words he is not fussed about redundancy. Hey ho.

[mavhc]

Fake break the server, see how bothered he is about it really.

[Techie101]

Fake break the server, see how bothered he is about it really.

 

And why would I do something as stupid as that???

[tmcd35]

Thats what I did, and he went with RAID 0. The server does not hold any critical data, each teacher is resposible to keeping all critical data backed up via memory sticks etc, the school also backs up daily onto several network drives. And if the server did go down the head is happy that it may be down for a few days in order to order parts and reimage the server, so in other words he is not fussed about redundancy. Hey ho.

 

I forsee tears inside of a year. But hey-yo you did your job, told him whats what and he didn't take your advice. Shrug your shoulders and walk away from it. But some poor teachers going to get it in the neck when their critical backup memory stick goes the way of all critical backup memory sticks....

 

EDIT: I probably would never have mentioned RAID level or given him the choice, as far as I'm concerned it's not his job. If he mentions it, depending on his character, I'd have either point blank refused to install RAID-0 or just plain lied - "Yes its RAID-0", not! But that's just me and I'm not advorcating getting yourself into trouble lying to the boss.

Edited May 28, 2010 by tmcd35

[Arthur]

Now I know it is normal to go with RAID 5 but the school wants performace over anything. So I am tempted to go with RAID 0 as both read and write speeds would be good, unlike RAID 5 where writes can be slow.

With respect, your head teacher is an idiot. As others have pointed out, RAID 0 is a very bad idea. A four drive RAID 0 array even more so. Most of the read/writes on your server will be random, so the speed increase is going to be negligible on a file server.

[Butuz]

Go with Raid 5.

 

DO not under any circumstances go with Raid 0 as that's fileserver suicide.

 

Butuz

[tmcd35]

'Official' advice by Intel, supplied with my new RAID controller -

 

RAID-0 - Disk Fails 0 - Read Speed Excellent - Write Speed Excellent

High Throughput Workstation

 

RAID-1 - Disk Fails 1 - Read Speed V. Good - Write Speed Good

OS, Apps, Entry Level

 

RAID-5 - Disk Fails 1 - Read Speed V. Good - Write Speed Good

Data, Web/Media Server

 

RAID-6 - Disk Fails 2 - Read Speed Good - Write Speed Good

High Fault Tolerance

 

RAID 10 - Disk Fails 1 per mirror - Read Speed V. Good - Write Speed Good

Database, File, Mail Servers

 

RAID 50 - Disk Fails 1 per R5 set - Read Speed Excellent - Write Speed V. Good

Database, File, Mail Servers

 

RAID 60 - Disk Fails 2 per R6 set - Read Speed V. Good - Write Speed Good

Critical Data

[mavhc]

And why would I do something as stupid as that???

 

To make him realise he doesn't mind spending the extra money. In general never give anyone a cheaper option that's going to cause everyone pain though, there's always money available, question is who do they give it to?