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Re: sleeping the system vs hibernate or suspend



On Wed, 05 Jan 2011 11:12:26 -0500, Toan Pham wrote:

> Here is the ref.  Please read paragraph at section "how much swap do i
> need?".  This article is pretty good for those who want to understand
> swap space.
> 
> 
> https://help.ubuntu.com/community/SwapFaq

Uh? :-?

Ah, now I realize what you mean... you are speaking about the recommended 
amount for the "/swap" partition but *not* when used in conjuction with 
hibernation, so that rule does not apply for what we are speaking here.

>From the above doc:

***
In reality, if you use hibernation you need what was outlined the 
relevant paragraph above, otherwise you need as much swap space as your 
system will use - which may be actually be very little in a modern 
hardware setup.
***

And the above paragraph says (bolded text is mine):

***
Hibernation (suspend-to-disk) 
The hibernation feature (suspend-to-disk) writes out the contents of RAM 
to the swap partition before turning off the machine. Therefore, *your 
swap partition should be at least as big as your RAM size*. The 
hibernation implementation currently used in Ubuntu, swsusp, needs a swap 
or suspend partition. It cannot use a swap file on an active file system.
***

Besides, that recommendation for the swap space is not nowadays right and 
it's easy to understand why. I have 8 GiB of physical ram:

sm01@stt008:~$ free -g
             total       used       free     shared    buffers     cached
Mem:             7          0          6          0          0          0
-/+ buffers/cache:          0          7
Swap:            2          0          2

So I can even work with no "/swap" at all and my system will be happy :-)

I think that rule is something similar to the windows one, which 
recommends having a paging file (pagefile.sys) of "1.5" of the installed 
ram, but with todays computers that is also a bit outdated.

> Sorry that i reference a Ubuntu source on this Debian mailing list.

No problem, but I'm afraid you were speaking about another different 
thing :-)

Greetings,

-- 
Camaleón


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