[Gllug] Discs for a RAID1 pair

Alain Williams addw at phcomp.co.uk
Mon Jul 4 16:52:10 UTC 2011

On Mon, Jul 04, 2011 at 04:36:00PM +0100, Chris Bell wrote:
> Hello,
>    I want to set up a new RAID1 pair of discs. I can have one Seagate
> Barracuda disc plus one Seagate Barracuda Green disc, or two Seagate
> Barracuda Green discs. Are there likely to be any unexpected problems with

Go for 2 of different batch numbers, different vendors is best.

> either combination? Should I try to disable the disc cache as a precaution?

Hmmmm, I tried that a couple of years ago, for the disks in the mirror I did

    hdparm -W 0 /dev/sda

What I found was that it made the system slower - no, I did no measurements, but
it really felt slower.

The other thing, more serious for me, was that it caused the mirror to break when I
got one of the disks dropping out with a not ready error (or something). Since they
were 1TB disks they took some time to be resynched. When this happened I first assumed
that I had bought duff disks and so replaced a couple of them ... before deciding that
that was not the issue and removing the hdparm stuff above. Since Oct when I did this
I have not had any issue.

Summary: don't disable the disk cache.

Alain Williams
Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  http://www.phcomp.co.uk/
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