| From: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, Scott Carey <scott(at)richrelevance(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Henrik <henke(at)mac(dot)se>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Filesystem benchmarking for pg 8.3.3 server |
| Date: | 2008-08-13 13:24:29 |
| Message-ID: | 48A2E08D.6000103@cheapcomplexdevices.com |
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| Thread: | |
| Lists: | pgsql-performance |
Scott Marlowe wrote:
> On Tue, Aug 12, 2008 at 10:28 PM, Ron Mayer ...wrote:
>> Scott Marlowe wrote:
>>> I can attest to the 2.4 kernel ...
>> ...SCSI...AFAICT the write barrier support...
>
> Tested both by pulling the power plug. The SCSI was pulled 10 times
> while running 600 or so concurrent pgbench threads, and so was the
> IDE. The SCSI came up clean every single time, the IDE came up
> corrupted every single time.
Interesting. With a pre-write-barrier 2.4 kernel I'd
expect corruption in both.
Perhaps all caches were disabled in the SCSI drives?
> I find it hard to believe there was no difference in write barrier
> behaviour with those two setups.
Skimming lkml it seems write barriers for SCSI were
behind (in terms of implementation) those for ATA
http://lkml.org/lkml/2005/1/27/94
"Jan 2005 ... scsi/sata write barrier support ...
For the longest time, only the old PATA drivers
supported barrier writes with journalled file systems.
This patch adds support for the same type of cache
flushing barriers that PATA uses for SCSI"
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