SSD, partition scheme...

[Martux]

Hello!
I am planning to use a ssd drive/64gb for my gentoo.
Now I am wondering, if my old partition scheme makes sense with an ssd too.
Right now, I have different partitions for
-ccache
-portage
-distfiles
-boot
-root
-home
Does it make any sense to use a similar scheme on ssd? I read that fragmentation is no problem?
That was one of the main reasons to split portage and ccache into seperate partition, as thes consist of may small files.
The root/home splitting is purely for backup/convenience reasons, as I sometimes nuke my system
So, what are your thoughts on this? Anything I maybe forgot? Reiserfs seems a decent fs choice?
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[Kollin]

https://forums.gentoo.org/viewtopic-t-828737-highlight-aligning.html
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[Martux]

Yeah, read that.
Orbiting Jupiter with some other guys
No really, I think my questions are a "bit" more generally...
Like, will give extra partitions to portage, ccache will wear out the disk faster, or does it make sense at all.
_________________
"Coincidence is God's way of remaining anonymous."
Albert Einstein
"The road to success is always under construction"

[bcward]

I just built a system with an intel x25-m g2 and I put /var/tmp/portage in a tmpfs. Additionally, I added

[broken_chaos]

What model of SSD is it? Some of them have much more effective wear levelling (like most of the Intel models) than others, meaning you can be a lot less careful about write/rewrite cycle and still get a fairly long lifespan out of it (some metrics say 5+ years on fairly heavy data loads for a good MLC flash drive).

Does the firmware on it support TRIM? If it does, you're best off using ext4 and 2.6.33 or higher with the 'discard' mount option. I think btrfs may also support TRIM, but I've heard it's, in general, still not stable enough for everyday usage (and probably is overkill on a desktop/laptop anyway). Remember to mount with noatime (unless you really, really, really, really need atime, in which case use relatime -- you probably don't need this, though). Also, don't use data=writeback if you want TRIM to work -- there's a bug that doesn't let it work! There are some more ext4 tweaks that can 'align' the data a little more, by making use of some RAID-intended features of ext4 -- see about halfway down this page, under "Filesystem Alignment". These tweaks are more important on lower-end drives with poor wear levelling, as it lets the filesystem do some of the work there.

As far as separate partitions go, it depends on the model. If it, as I mentioned before, has good wear levelling then splitting it up shouldn't affect the lifespan terribly significantly. If the wear levelling is poor, splitting it up may cause those sections of the drive (that are (re)written extremely often) to fail sooner than other segments.

An option for /usr/portage is to use the various squashfs (+unionfs/aufs) scripts that are around (or putting it on a mechanical drive or NFS share, if possible). I'd consider disabling ccache entirely (unless the performance hit is too great -- probably depends on your processor), if it is your only drive -- put it on a mechanical drive, if available, though (edit: or a tmpfs mount, as suggested above). If you have sufficient RAM (3-4GiB+?), I'd also put /var/tmp/portage on a tmpfs mount -- probably one with 1.5-2GiB of space is sufficient for anything but compiling OpenOffice (use openoffice-bin, if you need it). Same deal with /tmp, though that doesn't need anywhere near as much space as /var/tmp/portage.

Oh, and don't use swap, unless you have a tiny, tiny amount of RAM (or a mechanical disk to put your swap partition on).

There are also some per-application tweaks that would help, particularly if the drive's wear levelling/write amplification is poor -- like telling Firefox to not fsync multiple times for every page load (set toolkit.storage.synchronous to 0 in about:config -- note that this can lose any session data if you have a crash, like history or newly-saved passwords!). It may also help to put some application caches (again, like Firefox) on tmpfs -- such as by using tmpfs for /tmp and setting Firefox's browser.cache.disk.parent_directory to '/tmp'.

I'll be doing a Gentoo install to an SSD in a week or so, so I've been doing a bit of research. If you want some more tweaks/suggestions after I've done that, I'll be sure to post back with them.

[Martux]

Well, it's a Crucial M225 64GB, 2.5", SATA II (CT64M225) drive, which got decent reviews.
It should support TRIM and has 5 years warranty
I use tmpfs for /var/tmp/portage & /tmp since many years.
As this is mounting those dirs into RAM, what's the point putting ccache dir also to tmpfs?
My understanding is, that ccache is only usable when recompiling things often (which in fact on a ~amd64 system happens quite often).
As for the file systems, someone suggested using reiserfs with the mount option "barrier=flush".
Would that make sense? I like reiserfs a lot and use it on my hdds for many years, without ever having problems.
_________________
"Coincidence is God's way of remaining anonymous."
Albert Einstein
"The road to success is always under construction"

[broken_chaos]