RAID1, a failed disk and performance

Doug Poland doug at
Thu Jan 27 13:33:45 PST 2005

On Thu, Jan 27, 2005 at 03:14:46PM -0500, Chad Morland wrote:
> What happens in terms of performance when a drive in a RAID1 system
> fails? Will disk access be slower because it attempts to read/write to
> a failed disk or will performance be faster because it doesn't need to
> do half the work it usually does? I couldn't really find any online
> resources that deal with performance levels when there are failed
> drives present in a RAID array.
I recently set-up and tested a geom-based RAID1.  When I pulled a
hot-swap SATA drive from the server, I didn't notice any performance
degradation.  However, I must note that I wasn't running any monitoring
software nor gathering empirical data.  It's just my observation of the
responsiveness of the system while one drive was gone.  YMMV.


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