On 14/08/14 12:10, Ram Ramesh wrote:
On 08/13/2014 10:29 PM, Brad Campbell wrote:
On 14/08/14 01:25, Ram Ramesh wrote:
On a slightly different topic, will it be faster after a disk
fail/replacement as opposed to raid reshaping?
Much.
I just re-striped a RAID6 changing the chunk size from 128k to 64k.
This took 12 days all up. It's the seeking that kills it. To replace a
disk or do a resync on the same array takes less than 10 hours.
I am curious. Why do you have to change chunk size? What is the
benefit/advantage?
When I initially selected 128k it was for a stripe of 8 chunks (10
disks) and for a workload that contained lots of fairly big streaming
writes and reads. The array has since grown to 12 chunks (14 disks) and
the workload turned out to be a lot more random than I initially had
profiled, so I re-striped to attempt to reduce the amount of RMW
happening on the disks.
It may well be academic, but it's a lot easier to find 768k to write in
one action than 1.5M.
... and probably because I could.
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