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Re: [K12OSN] Need Help



Terrell Prudé Jr. wrote:

Are you sure? I have heard that RAID 5 is no good.
http://www.baarf.com/

I just looked at this.  Whoever these people are, they look to me to be
ranting.  It seems that, to them, nothing short of a multi-node cluster
filesystem would be enough for your average small-office file server! How easy it is to spend other people's money, eh? :-)

Write access is considerably slower on RAID5 and it tends to lock your heads together even for reads. I've always liked RAID1 for the simple reason that if everything is broken except one disk you can still recover the data it held. Plus if you do it in software you don't have to worry about having to match the controller to read on a different machine.

That said, RAID 5 kicks RAID 1 in the delicate parts when it
comes to performance.  Again, we're back to, say, six or eight spindles
vs. two spindles; no contest.

That's not necessarily true. If you configured those 8 drives in RAID1 pairs, you'd have 4 independently seeking places that could be writing at once and all 8 would be independent for reads. The trick is to arrange your data across the partitions so they are likely to be used simultaneously. These days you could just combine the RAID1 sets into one LVM, though.

> I've run many 14-disk SCSI RAID 5 setups,
and my God, they were quick!!  Yes, I'm assuming a real hardware RAID
card here; I generally don't recommend software RAID, no matter which
RAID level you use.

Software RAID1 works very nicely and does not add much overhead on SCSI where there is not much CPU interaction anyway. I probably wouldn't do RAID5 in software.

--
  Les Mikesell
   lesmikesell gmail com


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