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