Need help with RAID

[Missing Ghost]

Hi,
I have: 8x 36GB disks that I wanted to put in RAID5.
The controller that I want to use also supports RAID50, buy I never used this.
I would like to know....in what ways would it be better to use RAID50 instead of RAID5?
I can see that I would get an additional parity drive when using two raid5 arrays in raid0.

 

[Matthias99]

Originally posted by: Missing Ghost
Hi,
I have: 8x 36GB disks that I wanted to put in RAID5.
The controller that I want to use also supports RAID50, buy I never used this.
I would like to know....in what ways would it be better to use RAID50 instead of RAID5?

RAID50 creates two (in your case, 4-disk) RAID5 arrays, then stripes data between those two arrays as in a RAID0. Performance-wise, it should be slightly better, since the parity data is on two disks rather than one (so you can process two writes in parallel if they're on different arrays), but you're losing an extra disk worth of space.

I can see that I would get an additional parity drive when using two raid5 arrays in raid0.

Well, sort of. RAID6 gives you (effectively) two parity drives (so you can tolerate two drive failures and still be running). With RAID50, you can tolerate one failure per RAID0 array, so you have a 4/7 chance of surviving a second failure before you have replaced the first failed drive.

 

[Missing Ghost]

You mean that RAID50 is not really useful?
I need more capacity than speed since it's already fast enough for GbE.

 

[Matthias99]

Originally posted by: Missing Ghost
You mean that RAID50 is not really useful?
I need more capacity than speed since it's already fast enough for GbE.

It performs better, especially if you are queueing a lot of writes. It is also more fault-tolerant (although, as noted, it cannot always tolerate two drive failures).

If you just want the most capacity, use regular RAID5, or RAID0 (although then you cannot tolerate any drive failures, making this unsuitable for applications requiring high availability or for backup/archival purposes).

 

[Missing Ghost]

I don't really understand why there would be a performance increase... Still the same thing, but more complex and with 2 parity drives.....
I think I will go for RAID5.

 

[Missing Ghost]

I have another question about RAID. In RAID1, can you have RAID0 performance in reads? Does it reads half from each drive?

 

[Fullmetal Chocobo]

Best place for RAID explanations.