[CentOS] How to Increase Swap Memory in Centos 4.4?

[John Summerfield]

Bart Schaefer wrote:
> On 4/3/07, John Summerfield <debian at herakles.homelinux.org> wrote:
>> Bart Schaefer wrote:
>> > Eventually you should make a permanent swap out of a real disk
>> > partition, perhaps by adding a drive to the machine.
>>
>> Why?
> 
> That may be anoher "informed opinion" question.  I'm pretty sure that
> at one time it was the case that it was more efficient to swap to a

Arguably it was so, but then there's the convenience and the 
circumstances. The answers, I suspect, were always different between 
multidisk servers where one could dedicate a disk to the task, and the 
typical desktop system with one partition.

Take a CD-R someone's burned. You can see from the surface what's 
recorded on, what isn't.

Pretend the recorded-on bit is your data on the hard drive, the rest is 
the swap.

I reckon the kernel's footwork would have to be better than Fred 
Astaire's, to make up for the distance the heads have to seek back and 
forth.

A swap file could, of course, be at the edge of the recorded-on area, 
but then there's a good chance it's some place in the middle.

A means of placing a file in a "good" location would be handy.

However, one of the improvements in the 2.6 kernel is changes to 
swapping such that the partition no longer has the advantage.



> device than to a file.  Also at boot time it'd be nice to mount the
> swap before mounting the filesystems read/write.  And I would think

Why? How much swap do you need to run fsck?


> it's better to have all the swap in one continuous partition if you
> can.
> 
> Of course the other thing he could do is swapoff and remove the file
> once oracle is installed, on the grounds that the oracle engineers
> don't know what they're talking about.

Which is almost certainly the case, at least in some environments. If 
you can do disk I/O at four gigabytes/sec, swapping isn't nearly as 
harmful:-)





-- 

Cheers
John

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