Re: [GENERAL] Arguments Pro/Contra Software Raid - Mailing list pgsql-performance

From Markus Schaber
Subject Re: [GENERAL] Arguments Pro/Contra Software Raid
Date
Msg-id 4461FAD9.6020106@logix-tt.com
Whole thread Raw
In response to Re: [GENERAL] Arguments Pro/Contra Software Raid  (Bruce Momjian <pgman@candle.pha.pa.us>)
Responses Re: [GENERAL] Arguments Pro/Contra Software Raid  (Markus Schaber <schabi@logix-tt.com>)
List 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

pgsql-performance by date:

Previous
From: PFC
Date:
Subject: Re: [HACKERS] Big IN() clauses etc : feature proposal
Next
From: Scott Marlowe
Date:
Subject: Re: [GENERAL] Arguments Pro/Contra Software Raid