Subj : To RAID or not to RAID?
To   : astark
From : Angus Mcleod
Date : Thu Aug 19 2004 11:08 am

  Re: To RAID or not to RAID?
  By: astark to Belly on Thu Aug 19 2004 18:12:00

 >  Be> One more note of interest: IF YOU'RE RUNNING A RAID-0 ARRAY MAKE SURE
 >  Be> YOUR BACKUPS ARE RUNNING :)
 > 
 > Ouch! This is what I am going to be trying to get away from =)

The thing to remember is that RAID-0 and RAID-Linear are not really RAID at
all.  There is no redundancy in -0 and -Linear configurations, and in fact you
have REDUCED the reliability of your overall disk subsystem.  

Important to recall that the MTBF of an array is *LESS* than for the individual
component drives.  If you mirror two drives with an MTBF of 40,000 hours, then
the MTBF of the array is half, because you can expect *two* faults every 40,000
hours, or one every 20,000 hours on average.  More drives in the array reduce
the MTBF even more.

If you are going to build an array, and knowing that you have increased the
overall failure rate, it really does pay to use an array that introduces some
redundancy, such as RAID-1 or RAID-5.  That way the more-frequent-than-before
failures are acceptable, because failure occurs without data-loss.  Using
RAID-0 or RAID-Linear by itself (as opposed to combined with another scheme) is
pointlessly dangerous, IMHO.  You would be far better off using one, nice, new,
clean drive and replacing it with a new one as the MTBF approaches.

---
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