Raid-1 over three drives

supanatral

supanatral

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First of all, I would like to admit that this actually has to do with Windows Server 2003 x64 I'm not registered on any other site with a server section and I've grown to trust the users on this site so I thought I'd ask my question here instead of finding a new forum.

If I were to have RAID-1 (Mirroring) over 3 hard drives, would that add to better performance?
 
supanatral said:
First of all, I would like to admit that this actually has to do with Windows Server 2003 x64 I'm not registered on any other site with a server section and I've grown to trust the users on this site so I thought I'd ask my question here instead of finding a new forum.

If I were to have RAID-1 (Mirroring) over 3 hard drives, would that add to better performance?
Click to expand...

Mirroring does not influence (at least positively) your harddisk performance and adding more drives is i think not that usefull.

For performance increase, you need a raid configuration (i think 3 or 5), which splits information on at least 2 drives (write simultanuously half to drive 1 and half to drive 2). This would increase performance and when using 3 drives, you can replace a faulty drive and loose no uptime and/or data.

Good luck, Kees
 
Not really an answer to the question, but here's a great breakdown of some popular RAID types:

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

RAID 0 is striping without parity, meaning you get increased performance but no failsafe mechanism if one of the drives fail. RAID 1 is mirroring without parity, meaning you get no performance boost over using just one drive by itself, but you get data redundancy meaning you can preserve all data if one of the drives should fail.

The rest of the RAID types are simply extensions of these two basic types: RAID 5 employs a striping scheme with parity, meaning the drives in the RAID set are set up to stripe the data for increased performance, and a "parity" bit is written to each drive as well -- meaning that if ONE of the drives in the set fails, you can replace the drive and recover the data. It's one of the most popular RAID sets for increasing performance while maintaining a small measure of protection in case one of the drives dies.

In short, "mirroring" does not provide any performance boost (except for a small boost in read operations) -- it only provides data redundancy so your data is "safer" in case of drive failure.
 
Well, actually, if you have a RAID1 system implemented by software (as opposed to a RAID controller card) you will get increased overhead when writing because it has to write the data N (three) times. You will also only get performance INCREASE if your configuration supports split seeks, otherwise it won't make any difference.

The primary purpose of RAID 1 is the R in RAID: redundancy. It provides fault tolerance, but is not designed to improve performance. If you want fault tolerance and improved performance, choose RAID 3 or 5.

Choose RAID 3 or 5 will will also net you more space: RAID 1 mirrors data on all drives, so N times 500 GB drives will always give you 500 GB of total space, because the other drives are just copies. RAID 3 or 5 will give you N-1 x SIZE as long as they are all the same size. So, 3 500 GB drives will get you about 1 TB total space (as the space of the third drive is used for parity calculations).

RAID 5 would be best for you, probably, since it splits the parity among all three drives, whereas RAID 3 uses the Nth disk to store all the parity.

I use RAID 5 on my network file server.
 
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What's your overall system configuration look like? Is this a file server, directory server, etc? Personally, for boot drives in a server, I always use a RAID 1 mirror over two drives, if there isn't a hardware RAID card installed.

Michael
 
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