On 07/19/2010 04:49 PM, Neil Brown wrote:
On Sat, 17 Jul 2010 16:15:55 -0500
"Leslie Rhorer"<lrhorer@xxxxxxxxxxx> wrote:
I'm thinking about changing the chunk size on one of my arrays in
order to potentially improve performance. The man page rather suggests -c
is a vlaid option under Grow mode, although it doesn't specifically say
mdadm supports it under --grow. Is it indeed supported under mdadm 2.6.7.2
and kernel 2.6.26-2? Assuming so, I would like to know a bit more about the
change before issuing the command. Speficialy, what are the details of the
process? Does the entire (RAID 6) array have to be re-written, such as is
the case with adding a drive to the array? Does the recovery start
immediately? Can it be interrupted and then continue at a later time?
Yes, you can change chunksize with --grow.
I think you need mdadm-3.1.2 and kernel 2.6.32 though (version numbers might
not be accurate, but are close).
Yes, the entire array gets re-written just like adding an extra device.
The reshape does start immediately.
If you shutdown or crash, then on restart the reshape will pick up where it
left off.
I ran mine with mdadm v3.1.2 on 2.6.33.6-147.fc13.x86_64 (Fedora)
Too bad I screwed up the FS by shrinking the array too much beforehand -
now I have no idea whether it would've worked or not.
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