On 24/09/2011 14:17, Stan Hoeppner wrote:
On 9/23/2011 7:11 PM, Thomas Fjellstrom wrote:
On September 23, 2011, Stan Hoeppner wrote:
When properly configured XFS will achieve near spindle throughput.
Recent versions of mkfs.xfs read the mdraid configuration and configure
the filesystem automatically for sw, swidth, number of allocation
groups, etc. Thus you should get max performance out of the gate.
What happens when you add a drive and reshape? Is it enough just to
tweak the
mount options?
When you change the number of effective spindles with a reshape, and
thus the stripe width and stripe size, you definitely should add the
appropriate XFS mount options and values to reflect this. Performance
will be less than optimal if you don't.
If you use a linear concat under XFS you never have to worry about the
above situation. It has many other advantages over a striped array and
better performance for many workloads, especially multi user general
file serving and maildir storage--workloads with lots of concurrent IO.
If you 'need' maximum single stream performance for large files, a
striped array is obviously better. Most applications however don't need
large single stream performance.
If you use a linear concatenation of drives for XFS, is it not correct
that you want one allocation group per drive (or per raid set, if you
are concatenating a bunch of raid sets)? If you then add another drive
or raid set, can you grow XFS with another allocation group?
mvh.,
David
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