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On Thursday 22 April 2010 23:16:56 walt wrote: |
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> On 04/22/2010 09:52 AM, Alan McKinnon wrote: |
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> > On my web and mail servers I have no swap at all, they do have lots and |
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> > lots of RAM; my Sybase database servers have enormous amounts of swap... |
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> |
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> Hm. Does that mean your database servers are allowed to be slower than the |
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> web and mail servers? |
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No, it means that the database software intelligently handles swap. |
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An enterprise grade db like this one will load many megabytes of data in huge |
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chunks on and off disk in one action. If you are dealing with tables |
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containing many millions of rows, you really do want this behaviour. Without |
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swap, the db will still load and unload many megs of data at a time on and off |
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disk, so there is no appreciable downgrade of performance, but I do have the |
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benefit of keeping data in virtual memory for longer using swap. The database |
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code pages are never swapped by design - doing that is just plan stupid. |
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The web and mail servers on the other hand deal with millions of small files, |
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on the order of 10k each. Allowing that to swap is catastrophic. |
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-- |
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alan dot mckinnon at gmail dot com |
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