Single Drive vs RAID 1 vs RAID 5

[Logan]

For a server that hosts only a large messageboard, do you think a single drive, RAID 1 or a RAID 5 is most suitable? I've been researching some of the differences (ie: http://www.buzzle.co...-vs-raid-1.html) but can't really decide which is most appropriate.

[Aiwa]

Raid 5 or 10 are generally server architecture, as I recall. One drive can be swapped out and all of your data can be re-built. You also only lose about a drives worth of storage capacity.

You can use Raid 1, but you have to sacrifice exactly 1/2 of your storage capcity.

I wouldn't recommend a single drive for a server unless you do frequent backups.

[p4guru]

I'd only use raid 5 if you have a dedicated hardware raid controller with it's own onboard processor and cache. Otherwise chose raid 1 if those are only 2 choices.

But for large forums, only choice is 4x or 6x 15k scsi/sas disks raid 10

[Robulosity2]

With Raid 5 its 3 drives + spare. While the spare isn't an actual requirement, its usually pretty recommended

So if you had 3 x 500 GB drive you would actually only get 750GB of storage space (From what I remember)

This portion of this article may of of help http://en.wikipedia.org/wiki/RAID#RAID_10_versus_RAID_5_in_Relational_Databases

[Grumpy]

Something like a forum tends to have lot of writes. So, raid 5 will be useless. In strictly write performance, it's...
raid 5 >= raid 1 >= 1 drive.
In perfect theory where computation time is zero, all of their write performance will be equal.

Raid 5 is useful when your read requirements are as much as 10x higher than your writes (typical of websites actually) and you need the space. But this is rarely the case for a forum.

To increase write performance, your only choices are raid 0 and raid 10 (or 50 and 60... as they'll be better than no raid but that doesn't scale in write like 0 or 10. They'll stay at strictly less than or equal to 2x). But raid 0 is suicide... So, that only leaves raid 10. So, do raid 10 if you need the performance upgrade. Do raid 1 if you're on the budget and still seek some safety.
Software raid also does a very good job these days for raid 1 and 10 as they've improved a lot over the days. So, if you're gonna cheap out on hardware raid controller, just get software raid instead. You'll only beat software raid if you get a high end raid card with BBU for those two.

[Rhett]

Here is what I do.. R

Normal server Raid 1 SATA II
Mid level Raid 1 15K SAS
High end, high traffic Raid 10 15k SAS

[Luke]

You only use Raid 5 if you're willing to sacrifice read/write performance for redundancy and better space utilization. Raid 5 will not give you better read performance. Raid 6 is the same as Raid 5, but with an extra spare.

Raid 1 is strictly mirroring meaning each drive has an exact copy of the other. It will give you the best redundancy. Raid 0 is simply striping, which will give you capacity of the collection of disks. It will give you the best performance. Raid 10 (or otherwise known as Raid 1+0) is stripped first, then mirrored. It gives you the best of both worlds. But just like Raid 1, you can only use 1/2 your capacity.

So if you want redundancy, go with Raid 1. If you want performance go with Raid 0. If you want both do Raid 1+0 (you'll need at least 4 drives). Other Raid levels are typically more complicated.

There is also Raid 0+1, but I don't recommend it. Raid 1+0 offers better fault tolerance. This article provides the best comparison I've seen: http://aput.net/~jheiss/raid10/

http://en.wikipedia.org/wiki/RAID
http://en.wikipedia....ted_RAID_levels

Raid 10 is typically recommended for anything database driven. Raid 0 should give you similar performance, but you shouldn't use it with anything important like a server (unless you don't care about the data).

Either way, take backups/snapshots of your data offsite.

[Rhett]

Just a note... whoops... I needed some sleep it seems lol

[p4guru]

Just a note... RAID 10 - you will only have 25% of total drive space available... :smile: Takes 4 partitions/drives to equal one volume. :smile:

correction 50% ;)

i.e. 4x 300GB raid 10 = 600GB space available

[Rhett]

lmao late night...yes you are correct lol

[Dmacleo]

exchange server here (15-25 users) runs c on single (full backups twice daily using sbs2011 backup to dedicated drive) while exchange store/all databases/redirected folders on raid 5.
3 drives for raid 5, no spare in place but I can swap one in within minutes and still run.
c drive restore takes 20 min or so if needed.