Performance of COPY for Archive operations

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: <pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Performance of COPY for Archive operations
Date: 2004-09-14 23:54:04
Message-ID: NOEFLCFHBPDAFHEIPGBOCEIACEAA.simon@2ndquadrant.com
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I've spent a while working with PITR functionality on the Win32 port.

I noticed that *it works*, which is always great, but using a COPY command
the archival operation was significantly slower than the writing of the
xlogs themselves.

At one point, I got to being more than 10 xlog files behind with the list
growing steadily, and took a while to clear the logjam when my test
workloads completed. Not much point having archiving thats actually slower
than the writing of xlog....

IIRC the COPY command isn't the best thing to use for bulk-copying on
Windows, but I can't remember what is better. Anybody?

My tests were conducted on a small test server, but the imbalance between
xlog write/copy is worrying. I have 1 Gb RAM, which was nowhere near full
during testing. CPU was extremely low, so I'm guessing COPY has some bad I/O
characteristics.

Of course, I don't expect to be using COPY in production much...but others
will, so I want to sort this out. Feel free to point out the obvious....if
it exists,

Best regards,

Simon Riggs

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