On Sat, Feb 21, 2009 at 6:04 PM, John R Pierce <pierce@hogranch.com> wrote:
Kay Diederichs wrote:
> hdparm -tT tests one type of disk access, other tools test other
> aspects. I gave the hdparm numbers because everyone can reproduce them.
> For RAID0 with two disks you do see - using e.g. hdparm - the doubling
> of performance from two disks.
> If you take the time to read (or do) RAID benchmarks you'll discover
> that Linux software RAID1 is about as fast as a single disk (and RAID0
> with two disks is about twice the speed). It's as simple as that.
>


maybe with a simple single threaded application.  if there are
concurrent read requests pending it will dispatch them to both drives.

I'm waiting for a 10 hour backup to be completed before doing recovery on a server (ok recovery is a nice way to put it, truth is I gave up any hope of making the screwed LVM setup work and going to wipe/reinstall after the backup), I'll probably be able to try some tests.

However, I don't know enough to do this properly. So some questions:

Would running two CP command to copy 2 different set of files to two different targets suffice as a basic two thread test?

Is there a way to monitor actual disk transfers from command line without having to do manual timing?