Re: [gentoo-user] SDD strategies...

[Marc Joliet]

Am Mittwoch, 18. März 2020, 16:56:52 CET schrieb antlists:
> On 17/03/2020 05:59, tuxic@××××××.de wrote:
> > Hi,
> >
> > currentlu I am setting up a new PC for my 12-years old one,
> > which has reached the limits of its "computational power" :)
> >
> > SSDs are a common replacement for HDs nowaday -- but I still trust my
> > HDs more than this "flashy" things...call me retro or oldschool, but
> > it my current "Bauchgefühl" (gut feeling).

It really is an art to know when to trust your gut feeling :-) .  Thankfully 
in this case we have data!

> Can't remember where it was - some mag ran a stress-test on a bunch of
> SSDs and they massively outlived their rated lives ... I think even the
> first to fail survived about 18months of continuous hammering - and I
> mean hammering!

The German c't magazine did a similar test of various SSDs from different 
price categories, and they all showed the same result (I think some exceeded 
their lifetime by more than a factor of two, and the minimum was something 
like 1.5).

> > To reduce write cycles to the SSD, which are quite a lot when using
> > UNIX/Limux (logging etc) and especially GENTOO (compiling sources
> > instead of using binary packages -- which is GOOD!), I am planning
> > the following setup:
> >
> > The sustem will boot from SSD.
> >
> > The HD will contain the whole system including the complete root
> > filesustem. Updateing, installing via Gentoo tools will run using
> > the HD. If that process has ended, I will rsync the HD based root
> > fileystem to the SSD.
>
> Whatever for?

Yeah, I did the $PORTAGE_TMPDIR on tmpfs thing for a while, but I don't feel 
like "wasting" the RAM of my Gentoo systems in that way anymore.  And guess 
what:

# smartctl -x /dev/sda | grep -i lifetime_remain
202 Percent_Lifetime_Remain ----CK   092   092   001    -    8

This is for an SSD (Crucial MX500) that I've been using for about 1.5 years 
(since early November 2018), and which hosts the entirety of / (including /var 
and /home), only my media FS resides on HDDs.  The Crucial SSD I used before 
that (128 GB) was at 95 % last I checked, and I had been using that for about 
four years (it's laying on a shelf now for installation in my home server when 
I find the time for that).  (Oh, and everything is on BTRFS.)

> > Folders, which will be written to by the sustem while running will
> > be symlinked to the HD.
> >
> > This should work...?
> >
> > Or is there another idea to setup a system which will benefit from
> > the advantages of a SSD by avoiding its disadvantages?
>
> If you've got both an SSD and an HD, just use the HD for swap, /tmp,
> /var/tmp/portage (possibly the whole of /var/tmp), and any other area
> where you consider files to be temporary.

As I mentioned above, I'm not even doing that.  I did until about 2017, but 
stopped because it increased the load on my desktop too much for it to be 
usable during upgrades (poor old thing).

> > Background: I am normally using a PC a long time and try to avoid
> > buying things for reasons like being more modern or being newer.

Keep in mind we're talking about technology that is pretty old by now.  IIUC, 
what's new now is mainly that it's not niche anymore (see https://
en.wikipedia.org/wiki/Solid-state_drive#Development_and_history).

> > Any idea to setup such a sustem is heardly welcone -- thank you
> > very much in advance!
>
> Why waste time and effort for a complex setup when it's going to gain
> you bugger all.

I agree, I don't think a complicated setup like that is worth the effort.  I 
was really glad about being able to put the whole / on my SSD after I got a 
bigger one, just because of how it simplified things.

> The only thing I would really advise for is that (a) you think about
> some form of journalling - LVM or btrfs - for your root file-system to
> protect against a messed up upgrade - take a snapshot, upgrade, and if
> anything goes wrong it's an easy roll-back.
>
> Likewise, do the same for the rotating rust, and use that to back up
> /home - you can use some option to rsync that only over-writes what's
> changed, so you do a "snapshot then back up" and have loads of backups
> going back however far ...

Backups are something you should be doing anyway.  Even a local backup is 
better than no backup at all.  You won't miss your data until it's gone, and 
then you'll *really* miss it.

> Cheers,
> Wol

Greetings
-- 
Marc Joliet
--
"People who think they know everything really annoy those of us who know we
don't" - Bjarne Stroustrup