[OT] any tricks to boost performance of a read-only filesystem?

[Amedee Van Gasse (ub)]

On Sun, September 26, 2010 20:58, Robert P. J. Day wrote:
>
>   not specifically related to ubuntu, but i'm curious -- are there
> well-known ways to pump up the performance of a filesystem that is
> almost always mounted read-only?
>
>   it's well-known that, once you install everything on your system,
> then you should be able to mount the /usr filesystem read only -- at
> least until the next time you need to modify your installed packages.
>
>   now, for performance, once can always mount with "noatime" and
> "nodiratime" and that applies to any relevant filesystem.  but if your
> filesystem will be mounted RO *almost* all of the time, is there a
> particular choice of filesystem that will take advantage of that?

If you have enough RAM, you should be able to put the entire /usr in
memory. I don't know how exactly but I'm sure that Google knows.

I do something that is the opposite: I have /usr as a squashfs filesystem.

$ sudo du -ms /usr /.filesystems/usr
1396    /usr
464     /.filesystems/usr

After mounting the squashfs filesystem and deleting the old /usr I saved
932,7 MiB. This is on my netbook with an 8 GiB SSD, so that's a HUGE
improvement.
Of course it's a bit slower but I don't mind.

If you're interested, I used this as a staring point:
http://po-ru.com/diary/linux-liposuction-or-xubuntu-in-under-a-gig-on-the-eee-pc/
with a few changes.

-- 
Amedee