Re: [gentoo-user] Re: Dynamically change PORTAGE_TMPDIR via bashrc?

[Rich Freeman <rich0@gentoo.org>]

On Sat, Sep 26, 2015 at 10:08 AM, James <wireless@tampabay.rr.com> wrote:
> Florian Gamböck <ml <at> floga.de> writes:
>> Now, before I try some crazy stunts like bind-mounting $D and $ED on "preinst"
>> and cleaning up in "postinst", I wanted to know if some of you guys did
>> similar experiments and/or have some advice that you could share with me.
>
> I have been following 'bcache' as an interesting addition to complex
> compiling scenarios. I'm not certain how it will help your 'wild ideas',
> but it is worth a look, imho [1]

Honestly, I'm hard-pressed to think of situations where you're better
off with anything other than either tmpfs or whatever filesystem your
/usr happens to be on.

However, if you do want to build on something like bcachefs and you're
using an ssd you might just want to use a pure log-based filesystem
like f2fs.  You can afford to go far more experimental for temp space.
I haven't studied the design of bcachefs closely, so I'm not sure how
it would compare for this use.  I know it has made a bunch of noise
lately, though honestly I'm not impressed with some of the hype (not
something I blame the authors for - more the groupies).

One thing that both zfs and bcachefs seem to be doing (not that I'm in
an expert in either) is taking a multi-tiered approach to storage.
That is, writes can go into a durable log on a separate device and
then be consolidated onto more long-term storage.  I suspect that this
might help with some of the fragmentation issues that you run into
with COW.  Then again, I don't know how its performance would compare
to just dumping everything right to a single tier like btrfs and then
just periodically having some kind of smart defragmenter that just
cleans up the stuff that really needs it.

-- 
Rich