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Re: Problem identified: WAPL/RAIDframe performance problems
On Nov 28, 2012, at 6:02 PM, Greg Troxel <gdt%ir.bbn.com@localhost> wrote:
> Edgar Fuß <ef%math.uni-bonn.de@localhost> writes:
>>> I seem to be facing two problems:
>>> 1. A certain svn update command is ridicously slow on my to-be file server.
>>> 2. During the svn update, the machine partially locks up and fails to
>>> to NFS requests.
>> Thanks to very kind help by hannken@, I now at least know what the problem
>> Short form: WAPBL is currently completely unusable on RAIDframe (I always
>> suspected something like that), at least on non-Level 0 sets.
>> The problem turned out to be wapbl_flush() writing non-fsbsize chunks on non-
>> fsbsize boundaries. So RAIDframe is nearly sure to RMW.
>> That makes the log being written to disc at about 1MB/s with the write lock
>> on the log being held. So everything else on that fs tstiles on the log's
>> read lock.
> Do you see this on RAID-1 too?
> I wonder if it's possible (easily) to make the log only use fsbize
> boundaries, (maybe forcing it to be bigger as a side effect.)
Sure -- add fsbsize sized buffer to struct wapbl and teach wapbl_write()
to collect data until the buffers start or end touches a fsbsize boundary.
As long as the writes don't cross the logs end they already come ordered.
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig
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