optimal(?) layout of fedora 19 with one SSD drive and one regular HD?

Chris Murphy lists at colorremedies.com
Thu Dec 5 03:25:24 UTC 2013

On Dec 4, 2013, at 4:29 PM, Joe Zeff <joe at zeff.us> wrote:

> On 12/04/2013 03:21 PM, Tim wrote:
>> It's probably the reasoning behind make swap twice as big as RAM.  It
>> should leave enough room for RAM to fit into swap, and the wiggle room
>> for the OS to tidy up swap as it hibernates things.
> Sorry, but I have to inform you that you're putting the cart before the horse.  The rule of thumb I mentioned about making swap twice the size of RAM goes back to the early days of MS-DOS, long before there were such things as hibernate or sleep for computers.

Well there's more than one rule of thumb even on linux. And the paging method on DOS is different than NT, so it's surely different than linux, BSD, or OS X. Case in point, OS X has never had the idea of user configurable swap. The dynamic_pager process creates and destroys swapfiles on demand as needed. 

On linux, there have been periodic swap code changes, which can be found by doing an lkml search. New in 3.12 is a different block allocation algorithm for swap on SSD, for the 3.11 kernel is zswap, and frontswap has been in since 3.5 kernel.

The anaconda/blivet code suggests upwards of 3x memory if you have less than 4GB RAM and hibernation applies. Whereas for 8GB or more, the suggestion is 1.5x memory if hibernation applies. If hibernation doesn't apply suggested swap is between 0.5x and 2x RAM.

Chris Murphy

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