On Sun, Apr 18, 2010 at 12:04 PM, Eric Bergen <eric.bergen@stripped> wrote:
> Linux will normally swap out a few pages of rarely used memory so it's
> a good idea to have some swap around. 2G seems excessive though.
> Usually I prefer to have linux kill processes rather than excessively
> swapping. I've worked on machines before that have swapped so badly
> that it took minutes just to ssh to them. This is effectively a
> failure scenario that can last for a lot longer than it takes to
> restart/failover mysqld. For apache it means the clients will see
> errors until the load balancer health check drops the server out of
> rotation. The best solution in all cases is to keep an eye on swap
> in/out and memory usage so neither the crash nor the excessive
> swapping becomes a problem.
Umm, you were probably horribly over io utilized. Swapping by itself
will not kill perforance I have some boxes where mysql has leaked a
metric crap ton of memory and swapping is ok. The leaked memory is
swapped out and sits out in swap. Every now and a again I create more
swap to keep the server happy.
Swapping is often preferable to crash with unplanned downtime.
Note that innodb_flush_method can implact this...