Drive selection for gmirror

[Matthew Seaman]

On 28/04/2011 23:13, Ireneusz Pluta wrote:
> when selecting SATA drives for gmirror, boot device, connected to an
> on-board controller, should I look for so-called "enterprise grade", or
> "raid edition" drives (like for instance
> http://www.wdc.com/en/products/products.aspx?id=40), or I should rather
> focus on models closer to "consumer grade"? Will gmirror configuration
> significantly benefit from things like TLER, or it would rather be
> harmful, like when using these disks as single ones in desktop
> applications?

gmirror doesn't do all of the really fancy stuff an expensive hardware
RAID card will.  So, if one disk in a mirror fails a write, the mirror
breaks and has to be resynch'd.  With gmirror that means manually
entering a sequence of commands to remove and re-add the drive to the
gmirror.

"Enterprise" grade drives can be much more reliable over all as they are
designed for 100% duty, whereas with consumer grade the expectation is
that the drive will be turned off much of the time.  This is typically
one of the distinguishing features between SAS and SATA as well.
"Green" drives can be particularly bad with FreeBSD, as they frequently
end up spinning up and down continuously, which both wastes a lot of
power and also shortens the life of the drive: neither of which adds to
the actual (rather than claimed) green credentials of the device.

Decide how much disk space you want, and what your budget is, then buy
the best quality drives that match your criteria.  I'd turn off TLER.

	Cheers

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW

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