On Tue, 29 May 2007, Heikki Linnakangas wrote:

The checkpoint will take at least a couple of seconds on any interesting system, so 0.1 s resolution should be enough IMHO.


You may be underestimating the resources some interesting systems are willing to put into speeding up checkpoints. I'm sometimes dumping into a SAN whose cache is bigger than the shared_buffer cache in the server, and 0.1s isn't really enough resolution in that situation. A second is a really long checkpoint there. Since even that's limited by fiber-channel speeds, I know it's possible to do better than what I'm seeing with something like a PCIe host adapter having on-board cache in the GB range (which isn't that expensive nowadays).

Also, even if the checkpoint total takes seconds, much of that is in the sync phase; the write time can still be in the small number of ms range, and I wouldn't want to see that truncated too much.

Anyway, I have a bunch of data on this subject being collected at this moment, and I'll rescale the results based on what I see after analyzing that this week.

--
* Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com Baltimore, MD

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