Re: [gentoo-user] swap on ssd?

[William Kenworthy]

On Mon, 2012-11-26 at 09:17 +0100, Florian Philipp wrote:
> Am 25.11.2012 23:46, schrieb William Kenworthy:
> > Has anyone tried swap on ssd?  - has it killed the drive prematurely? -
> > any other effects?
> >
> > I have a system that is maxed with with 4G ram and tends to use swap
> > heavily at times which slows things down ... so I am thinking a small
> > ssd might help here.
> >
>
> You should tell us which model you want to use. In any case, if it is
> relatively recent, I don't think you can actually break it with write
> cycles anymore unless you keep it 100% busy 24/7.
>
> > Another slower alternative is a usb thumbdrive ... might try that later
> > today as I have some around ... again anyone tried this and found
> > something unexpected?
> >
>
> Thumbdrives have much simpler wear leveling. They also use triple level
> cells (TLC) which are even worse than the MLCs found in cheaper SSDs.
> Not to forget that USB doesn't support proper DMA and therefore
> increases CPU load. Long story short: Swapping on thumbdrives is as fast
> as a snail riding a turtle -- but turtles have a longer life span.
>
> Another idea:
> You can try to reduce the swap load by using frontswap with zcache. It
> compresses memory pages in RAM which would otherwise be swapped. You
> still need swap but less often.
>
> Enable
> FRONTSWAP
> CRYPTO
> CONFIG_STAGING
> CONFIG_ZCACHE
>
> then add "zcache" to your boot parameters.
>
> Regards,
> Florian Philipp
>

Now thats interesting, more knobs to twist/buttons to push :)  

Thanks for that info!

My original question was on writing to swap destroying ssd's - but I
seem to remember that problem was more hot air than fact - born out by
the fact that no-one has jumped with an actual failure.  My work macbook
air (gentoo of course) has swap on the ssd, but with 8G ram its hardly
ever used unlike my home desktop/server which I am talking about here.
I did try an early intel ssd for a week (only drive in a dual core atom
system) before I had to give it back and it was certainly FAST.

Ive just had a a 500G drive expire so the hobby cash I was going to use
for the ssd has gone on a new WD 2TB - next month then :(

Was pushing a load of 109 at one stage trying to sync a small cephfs
cluster with one osd on the failing drive.

Yes, I would love to upgrade, but its also a good learning experience to
keep pushing the old rig - I dont get to play with this stuff otherwise.

Maybe Santa will call this year ...

BillK