[rhelv6-beta-list] My first experiences with RHEL6 beta

[James Findley]

Regards,
James Findley
Support Manager
+44 (0) 7717 664 986
james.findley at trans-axion.net
Trans-aXion Limited

On 06/15/2010 02:46 AM, John Summerfield wrote:
> Bryan J. Smith wrote:
>> John Summerfield wrote:
>>> When I do want swap, I usually want a swap file, not a
>>> swap partition. Swap files are more flexible, they can
>>> be created and dispensed with at will. Its a minor task
>>> to add a swap file, provided only that disk space is
>>> available. It's even easier to dispense with swap and
>>> assign the recovered space to other tasks.
>>
>> Most of this argument is mitigated thanx to volume management
>> (i.e., LVM).
>>
>> As far as swap file v. swap partition, that goes into the same
>> category of filesystem free reservations, segmentation of
>> filesystems, etc... You are free to prefer what you wish, but
>> "best common practices" of 40 years of POSIX/POSIX-like
>> implementations tend to favor some sound reasons why we have
>> such things as: - swap partitions
>> - filesystem free reserevations
>> - segmentation of filesystems
>> - etc...
>>
>> And, again, liberal usage of LVM tends to make most arguments
>> on the matter quite moot in "Enterprise" Linux. My $0.02.
>>
>
> I would venture to suggest that most systems running Linux, especially
> those with IA32 or AMD-64 CPUs, have a single disk. I cannot see that
> LVM provides any benefit in such cases.

You can suggest anything you want.  Doesn't make it correct.  And I, 
personally, find LVM very useful even if I only have a single disk. 
Perhaps if you learned to use it better, you might come to appreciate it 
more.

>
> I used to use OS/2. If you check googlism.com you will find vestiges of
> my reputation there. on OS/2, which never had swap partitions, the
> recommend placement for swap is "the busiest partition on the least busy
> drive."

Lovely.  RHEL (and linux in general) are not similar to OS/2 in any way. 
  So this is irrelevant.

>
> The "least busy drive" needs no explanation, but people do tend to choke
> on their weeties at "the busiest partition."
>
> reflect a moment. At a random instant, where are the drive's heads
> likely to be? I suggest over the latest read or write operation. Where
> is that, usually? Someplace in the busiest partition.
>
> It does not matter what OS you use, the above is true.

Yes it does matter, actually.  Linux under normal conditions only uses 
tiny amounts of swap, as certain dirty memory structures are much faster 
to flush if they can be swapped first - but this only takes a few KB at 
most.  On modern disks swap IO should be negligible unless you're 
running _way_ out of ram.  Which you shouldn't be doing.  So you can put 
it wherever you want.
There is a (small) overhead for using file-based storage as opposed to 
volume based storage, and given that (if you know how to use lvm) file 
based storage isn't really any more flexible, noone cares about it.

-James