[svlug] Question about RAID

Gary Lin glin at bugfamily.com
Thu Oct 24 11:48:28 PDT 2002


Thanks for all the replies.. Forgot to send another follow-up e-mail
to let you guys know what happened to my system.  I decided to use
Linux's RAID rather than the driver from Promise (Thanks for letting
me know that Promise is also a software RAID), so that I wouldn't tie to
the vendor.  However, though, I had a horrible time installing RH7.3. =~~~
The failure happened everytime the installer tries to eject the DISC2 and
ask for DISC3.  Don't remember the exact error message, but I remember
it is saying something about the Device is busy.  Seems like there is
a bug filed on this issue, but never really get resolved.. =(  Oh well,
after installing for over 10 times, I am finally able to get it installed
on my machine and everything is up and running now.  Thanks guys!

Oh, also, thanks for Marc for putting up the performance measurement for
software vs hardware RAID.  Very interesting.  
-- Gary 

> 
> On Mon, Oct 14, 2002 at 02:36:07PM -0700, Rafael Skodlar wrote:
> > On Mon, Oct 14, 2002 at 02:28:18PM -0700, Aaron T Porter wrote:
> > > On Mon, Oct 14, 2002 at 01:54:19PM -0700, Rafael Skodlar wrote:
> > >  
> > > > Use hardware RAID whenever possible. Why waste CPU cycles on doing
> > > > things that controller is supposed to do.
> > > 
> > > 	Because in many cases you'll get better overall performance using
> > > Software Raid than relying on the 33mhz processor on your raid card. Not
> > > such a big deal with Raid 0 or 1, but when you use raid5 you really start
> > > to see a difference.
> > 
> > Is that "somebody says so" or a fact? I would like to see the stats.
> > URL? It's my guess that controller were designed so that the CPU can
> > handle the load for a particular SCSI bus. That means you won't gain
> > much if anything at all to shuffle blocks all the way to CPU from
> > the disks on the same bus.
> 
> As far as I'm concerned, it's a fact.
> http://marc.merlins.org/linux/misc/raid.txt
> 
> All the Raid cards have seen have too slow a CPU/XOR unit to compete
> with software raid for Raid 5.
> That doesn't mean, they don't exist though.
> 
> Marc
> -- 
> "A mouse is a device used to point at the xterm you want to type in" - A.S.R.
> Microsoft is to operating systems & security ....
>                                       .... what McDonalds is to gourmet cooking 
> Home page: http://marc.merlins.org/   |   Finger marc_f at merlins.org for PGP key
> 
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