On Sun, Aug 23 at 14:11, Tristan Ball wrote:
Hang on, in reading that his initial results were 50 writes a second, with
the default xfs write barriers, which to me implies that the drive is
honouring the cache flush. The fact that write rate jumps so significantly
when he turns off barriers, but continues with ODIRECT and
innodb_flush_log_at_trx_commit=1 to me just says that xfs is returning
success on writes as soon as the data has been given to the drive - not
when the drive has flushed it's cache to have it persistent. Given that we
told xfs to turn off write barriers - isn't it doing what it's told? Why
are we expecting data to be consistent across power loss or device
removal?
Couldn't this just be XFS only actually requesting cache flushes when
barrier's are enabled?
Yea, I parsed the article the same way.
50 IOPS with xfs barriers (crappy by any standard)
5300 cache-enabled IOPS or 1200 cache-disabled IOPS with the X25-E,
and he tried yanking the power while doing work with cache disabled
and it didn't lose any transactions.
Seems like it was behaving as expected, unless I misunderstood something.
--
Eric D. Mudama
edmud...@mail.bounceswoosh.org
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