| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Marco Colombo <pgsql(at)esiway(dot)net> |
| Cc: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, Ben Chobot <bench(at)silentmedia(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Jack Orenstein <jack(dot)orenstein(at)hds(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Maximum transaction rate |
| Date: | 2009-03-13 16:23:43 |
| Message-ID: | 5459.1236961423@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Marco Colombo <pgsql(at)esiway(dot)net> writes:
> And I'm still wondering. The problem with LVM, AFAIK, is missing support
> for write barriers. Once you disable the write-back cache on the disk,
> you no longer need write barriers. So I'm missing something, what else
> does LVM do to break fsync()?
I think you're imagining that the disk hardware is the only source of
write reordering, which isn't the case ... various layers in the kernel
can reorder operations before they get sent to the disk.
regards, tom lane
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