[ale] Disk IO Question

[Greg Freemyer]

On Thu, Oct 29, 2009 at 4:49 PM,  <mmillard1 at comcast.net> wrote:
> I have a Suse OES server running on an IBM 346with 2 gig of RAM.  I've
> installed two Addonics Multilane SATA cards connect with Multilane cables
> to external SATA enclosures housing 4 WD Caviar Green 1.5 TB Drives.
>
>
>
> I have about 1.8 TB of Data on one Enclosure which changes daily.  My plan
> was to copy the 1.8 TB to the second enclosure daily and send the drives in
> that unit off site.

How are you copying?  dd, rsync, cp --archive, etc.

> My expectation was that by having 4 independant SATA paths per unit
>  would give me substantial performance when moving data between these units.

I agree.

> I'm seeing a constant speed of about 60 gig per hour.  This is much slower
> than I expected.  Have any of you done anything like this? Is this the kind
> of performance I should expect?  Hopefull some of you bright people can
> share some wisdom with me.

60 GB per hour may or may not be slow.  If the files are very small, I
find 100K files / hr to be a limiting factor in some cases.

I also do a lot of "dd if=/dev/sdb of=/dev/sdc bs=4k
conv=noerror,sync" copying of filesystems.  I see speeds of 250GB/hr
even with just drive to drive transfers.  You raid array should be
much faster.

So if you can unmount your primary drive every night, you should be
able to make a dd copy every night.  I have one vendor that is telling
me they are moving data around at 1TB/hr.  (I'm not sure how true that
is.)

Greg