| From: | Markus Schaber <schabi(at)logix-tt(dot)com> |
|---|---|
| To: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
| Cc: | "Pgsql-Performance ((E-mail))" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: [PERFORM] Arguments Pro/Contra Software Raid |
| Date: | 2006-05-10 14:38:17 |
| Message-ID: | 4461FAD9.6020106@logix-tt.com |
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| Thread: | |
| Lists: | pgsql-general pgsql-performance |
Hi, Bruce,
Bruce Momjian wrote:
>>It does not find as much liers as the script above, but it is less
>
> Why does it find fewer liers?
It won't find liers that have a small "lie-queue-length" so their
internal buffers get full so they have to block. After a small burst at
start which usually hides in other latencies, they don't get more
throughput than spindle turns.
It won't find liers that first acknowledge to the host, and then
immediately write the block before accepting other commands. This
improves latency (which is measured in some benchmarks), but not
syncs/write rate.
Both of them can be captured by the other script, but not by my tool.
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org
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