Stef Telford wrote:
[snip]
> during resync's on raid-1 the mirror will not be available.
I'm not sure I understand this. md/raid1 devices are accessible while
resync is occurring...albeit with lower I/O throughput since the resync
is consuming bandwidth.
It seems relevant to add that in this situation, it would have helped to
have a logging or bitmap capability in raid1 in order to speed up the
resync (I think Brian Schwarz was trying to allude to this, but sort of
missed the point... :).
For anyone who wants faster resync times, you could try Peter T.
Breuer's fr1 ("fast intelligent" raid1) patches against the raid1
driver. These provide the driver with a bitmap capability, which ensures
that only dirty data blocks will be resynced (rather than the whole
device/partition, which is currently what md does).
I'm also currently working on some enhancements to that code to allow
the bitmap to be persistent (stored on disk), so that resyncs will
always be "intelligent" or "fast", even after a reboot or failure of the
server. I'm hoping that this enhanced code will be able to make its way
into the mainline kernel some time in the not too distant future...
*fingers crossed*
--
Paul
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