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Date: Mon, 22 Jul 2013 03:23:11 -0500
From: Dale <rdalek1967@gmail.com>
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Subject: Re: [gentoo-user] more on SSD: swap
References: <20130721113141.6be7f5ad@acme7.acmenet> <51EC5E5D.1050100@iinet.net.au>
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William Kenworthy wrote:
> On 21/07/13 22:31, luis jure wrote:
>> OK, now i have my system successfully installed and running on my new SSD.
>> now i have to decide what to do with the rest of the disk (it's a 256MB
>> samsung).
>>
>> the first big question is: what about swap? i found some web pages
>> (perhaps old) stating that it's not wise to put swap on the SSD because of
>> all the read/writes. but apparently from what i read on the recent
>> thread on this list, that shouldn't be much of a concern now.
>>
>> i also read somewhere that if you have swap on the SSD and want to avoid
>> unnecessary read/writes, you can reduce swappiness. i have 12GB RAM and i
>> think normally i don't really need swap space on disk, so i thought that
>> could be a good idea.
>>
>> so what i'm planning to do now is:
>>
>> - put swap on the SSD
>> - reduce swappiness
>> - put /var/tmp/portage on tmpfs
>>
>> so, do you guys think that's a good setup?
>>
> swap: this will make one of the bigger speedups to the system when you
> need swap. swap is good - yes you can do without it, but the day comes
> when you REALLY do want it, and ... [crash!] ... otherwise it can just
> sit there waiting :)
>
> /etc/sysctl.conf:
>
> #vm.swappiness=1
> #vm.vfs_cache_pressure=50
>
> these were recommended to me for running vm's and seem to do the job
> (usually I am running with a several GB of swap (16G ram, 16G swap) in
> use ... these settings definitely minimise it though big rsync jobs
> stall when it fills ram+swap.
>
> /var/tmp/portage is a more difficult one ... a long thread way back
> (Dale, I think you were in it) looking at speed showed there was no
> speed advantage to compiling in tempfs because spinner) disk caching was
> so good the data only hit the disk when necessary. I presume the same
> will apply with compiling and SSD's in that the actual writes will be
> minimal (in the scheme of things) so it shouldn't be a worry. My
> experience with compiling in tempfs is that it works, but has a much
> higher failure rate than on disk - i.e., things like OO/Lo, KDE, gcc and
> glibc have large space requirements that you must make sure tmpfs can
> satisfy before you start. And if its a busy machine actively using lots
> of ram it gets "hard". I am making the point that most machines today
> are way overprovisioned but when you are near the edge, saying things
> like I gave xGB ram and never needed swap, so you wont either is
> misrepresenting the situation.
>
> BillK
>
>
Yes, I did so some testing on whether portage's work directory on tmpfs
instead of HDD was faster or not and it wasn't much difference. I
actually had a couple times where it was faster on HDD but could have
been that some other process took up a few seconds of time too. The
difference was literally seconds on compiles that were between 30
minutes to one hour.
Dale
:-) :-)
--
I am only responsible for what I said ... Not for what you understood or how you interpreted my words!