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Old 01-17-2006, 04:13 PM
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StephaneM StephaneM is offline
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Join Date: Dec 2003
Location: France
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Re: Things that make me go "Hmmmm"

Quote:
Originally Posted by queonda
Sounds like you've been messing around with Raid for a while (i don't mean the bug spray)
I use them for work : RAID5 for database server, RAID 1 for other servers.
Quote:
I've heard of 1+0 is a good raid. What's your opinion?
It's depend on your budget and what you want to achieve, so I'll begin with a few facts :

RAID0 = you distribute your logical volume betwen drives, with no redudancy (loose one drive, you loose everything). This is used for maximum write/read performance. Minimum two drives.

RAID1 = Mirroring, you copy drive content onto another one. Redundancy is great. Performance are good for reading, fair for writing. You loose 50% of drive capacity (two drives)

RAID5 = Distribute logical volume between at least three drives with parity. A block of data is written on drives like this : Part A on drive A, Par B on drive B, Parity on drive C. A and B are the useful data, C only helps reconstruct A or B with the remaining one. A,B,C are not always on the same drive for better peformance. Redundancy is great. Performance are very good for reading, fair for writing (poor reading / writing when rebuilding). You loose 30% of drive capacity with three drives (25% with four, 20% with five and so on)

RAID 0+1 or 1+0 = you combine a mirrored volume with a spanned volume. Either you span a volume on two mirrored volumes, or you mirror two spanned volumes. Performance are good for reading and writing. Redudancy is great. You are loosing 50% of drive capacity (four drives)

So RAID 0+1/1+0 achieve the best performance for a redudant solution, but for a higher cost than RAID5.

I personally choose RAID5 because

* I do find performance to be enough for HTPC
* It's cheaper
* Only three drives needed, HTPC cases are generaly limited in space and also it is always recommended to have a dedicated power line (from the PSU) to each drive: for redudancy reason and also because two drives on the same power line can issue a failure of one of the drive (power drain).

Regards,
Stéphane.
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