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Re: [K12OSN] Software RAID



On Fri, 6 Dec 2002, Shawn Powers wrote:

> A tiny bit of background before I ask my question to the group:
> 
> I have 2 file servers, both just midrange PIII Dell workstations (due to
> budget) that run netatalk.  I realize this isn't the netatalk list, but
> LTSP has the same type of serverload that my mac clients put on our
> servers.  Tons of tiny preference files are constantly updated, copied,
> etc.  (In fact, I've never had anything hammer on a file server like
> Macintosh Manager's preference system, but that's another story...)
> 
> While the network card is only 100Mbit, I think the bottleneck in my
> systems are the hard drives (just IDE drives, no cash for SCSI here!)  If
> I use software RAID (striped, I forget if that's 0 or 1) might it increase
> my server's ability enough to tackle the chore?  (And make it worth my
> while to work over the weekend to make it happen. :)

At the risk of ignoring what you've already said (i.e. you can't afford 
SCSI hardware), I'll go ahead and recommend that anyway.

In my experience, disk I/O degrades much more "gracefully" on SCSI than on 
IDE. I chalk it up to the little/no CPU overhead of SCSI, command 
queueing, generally higher RPMs, and more intelligent controllers. At any 
rate, IDE totally chokes when asked to do multiple tasks.

Rather than futz w/ unreliable RAID 0 schemes, suck it up and buy some 
SCSI gear. Gawd, I can't believe I'm going to say this, but, "You can't 
afford NOT too."

File servers can be fairly low-end in virtually all other respects. RAM is 
always nice, but CPU usage is pretty low on all of my file servers. Disk 
I/O is king here. We've got a bunch of dual P-Pro 200 and 180s that feed 
files using samba and netatalk. CPU usage simply isn't an issue with 
these. We do software RAID 1 and RAID 5 on these, w/ 7200 RPM SCSI drives.

But, as they say, to each their own. Have good backups. Cheers,

-Dan Young
-Parkrose School District





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