How to choose the size of swap?

[Vladislav V. Prodan]

We have several servers with 8|16 GB of memory, 2|4 harddrive
(RAID1|RAID10 using ZFS)
These servers will work with Mysql, the size of databases that are
several times larger than the size of memory.

What would recommend to expose the size of swap?
On a separate partition or a file?
At hand is not loaded with servers that have the swap was over 20 MB ...
In an extreme case, let the output "top v" to this maillist


-- 
Vladislav V. Prodan
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vlad11 at jabber.ru