swap - 2 HDs

[Alex Zbyslaw]

Will Maier wrote:

>On Fri, Dec 16, 2005 at 09:33:57AM -0300, Aguiar Magalhaes wrote:
>  
>
>>Is It recommended to configure  swap area in both HDs ?? 
>>    
>>
>
>I don't see the point -- swap is where pages that don't fit in your
>real memory go. It's less optimal than real memory in terms of
>latency, but I don't see how two disks would make swap performance
>much better.
>  
>
This is contrary to the "usual" advice which is to split swap across 
disks AFAIK.  I've never done any benchmarks, but my gut feeling would 
be that if the disks were on separate controllers, and if the machine 
did swap regularly then two swap partitions would be beneficial.  Even 
on the same controller it could easily make a difference since 
individual IDE/SATA disks can't actually reach the performance of the 
channel as a whole.

Given that these are large hard disks, what's 2 or 4Gb in the grand 
scheme?  A drop in the ocean, so I would (and do) put swap on both.

Of course, if the machine actually swaps regularly then investing in 
more RAM would give the best performance!

--Alex

PS If the two disks are larger than your actual needs, then you might 
want to consider emergency scenarios like one of your disks dieing.  If, 
for example, you put a spare, bootable version of FreeBSD on the 2nd 
disk to aid recovery then that OS will need a swap partition anyway and 
you might as well use it regularly.  $0.02