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Re: RAID 0 risky ?

Technically speaking drives don't _wear_ out... Bad sectors are generated because at some time the disk surface has been damaged, usually by the heads hitting the disk. And many faults to do with the components on the controller board can be traced to a poor supply of power (eg spikes and brownouts, a UPS will help resolve this)

Other than that, RAID 0 is more risky than a single drive as you have no fault tolerance (one drive fails and you lose all the data on al the drives), and you have three times the chance that one of the drives will bomb for whatever reason. Since it is for mail storage (an inherantly difficult data source to back up), I would say using RAID 0 would be a VERY bad idea, especially since you mention IMAP (eg mail stored on the server). If one drive fails every user you have loses their mail.

I would think RAID 5 would be the better system to use in this instance.

To follow you usage question a little. Lets assume you want to write 256k to the array.

(We assume 64k block size for all arrays)

In a RAID 0 situation the first drive would have 128k written and the other 2 would have 64k written to them.

In RAID 1 (using 2 drives) each drive would have 256k written to them.

In RAID 5, each drive would have 128k written. There would be 2 x 64k written to the 2 data drives, as well as another 128 on the parity drive (for this particular write).

This is simplified but correct, from here we can see that RAID 1 would have the highest usage patterns per drive, next would be RAID5 and finally RAID 0. This is of course the price you pay for redundancy, you have to replicate the data somehow. RAID 5 obviously does the least replication while still keeping fault tolerance, although it does cost a small amount of computing power (not a problem if you have a RAID card)

Hope this helps

At 00:09 20/03/2002 -0500, Thedore Knab wrote:
Is RAID 0 that risky anymore for data storage (IMAP mail files) ?

I figure that under normal wear and tear a drive should last about 5 years.

Does this sound right ?

I have 3 IBM SCSI 18GB drives.

With RAID 0, I get 51.5GB of storage space.
With RAID 5, I only get 37 GB of space with 20% wasted overhead.

RAID 0 and RAID 1 are less work for the disk volume than RAID 5.

So in an ideal world, volumes with RAID 0 or RAID 1 will last longer than
volumes in RAID 5.

Thus, it would be less risk to use RAID 0 or better RAID 1 than RAID 5.

Ted Knab

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