Very Computer

Hi there,

are there differences in performance?
assumed they have the same access speed.

What about having more than one controller?

what do you think?

Thanks for answer
Martin

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Four 1G drives should have better throughput under linux than 1 4G drive.
In fact if you are running disk intensive stuff (news feeds) there is
a clear advantage in going with the smaller drives.

As far as two controllers goes it will make a difference if you are
running more than something like 25% of channel capacity on your single
controller.

A good SCSI controller will queue up requests. These requests can
execute much more quickly on independent devices. If you want it
to really scream I think that there are some recent kernels which allow
for striping.

-clint

--

Clint Schneider

 MH> are there differences in performance?
 MH> assumed they have the same access speed.

Spreading things out on different drives gives pretty much more performance.

 MH> What about having more than one controller?

Or a controller with more than one channel. Gives even more performance,
provided the disk(s) are fast enough to flood the channel.

 Knet

Quote:>>>>> Martin Heinz writes:

MH> are there differences in performance? assumed they have the
MH> same access speed.

Go for multiple disks and use "md" (RAID0)

It may lower the MTBF but you must keep a comfortable margin since modern
driver are robust.
Be VERY CAREFUL: heat can kill a disk and will be more difficult to exhaust
with 4 drives.
Also think that the machine will be much more noisy.

MH> What about having more than one controller?

Depends on the nature (fast, wide ?) of the involved SCSI and of the type
of utilization (burst reads ?, writes ?, long continuous read ... ???)

This debate is interesting but not peculair to Linux.

So back on topic: I'm only using 2 EIDE under "md" RAID0, read performance
is slightly better but write speed is amazing (more than 6MB/s on ext2)

--
Nat

 NM> So back on topic: I'm only using 2 EIDE under "md" RAID0, read performance
 NM> is slightly better but write speed is amazing (more than 6MB/s on ext2)

Perhaps this is not the right group for this discussion (you may mail if you
want to), but does "md" write four bits of every byte
to different disks, or how does it aquire such speed?

Would 4 disks give even more performance?

How about buffers and "md"?

Interested. :)

 Knet

Well, having your swap on one drive, and your system on another would give
better performance (less head seeking).  However the bigger drives tend to
have higher specs.  I got a 4GB Quantum with 2MB RAM cache.  It spins at
7200rpm, and a bunch of other specs which made it pretty attractive.  A
second drive would be nice for swap, but I'm not dying for disk
performance here.

Other than that, it depends on your application.  You might have an
application which requires two heavily stressed file paths.  By locating
them across multiple volumes you can get several sets of heads working for
you rather than just the one.

cya
Craig.