Using USB Memory Stick to Improve Performance

[Siggy Brentrup]

Hi List,

I'm top posting this because for the time being I don't have a
well connected web site available.  If you are not interested
or already know this stuff, simply skip over this message.

With my now comparatively low end Vaio laptop that I'm running Ubuntu
on I experienced a lot of interrupted music and freezing GUIs during
the past weeks.  I found out that this is primarily caused by disk
accesses to mmap'd shared libraries involving slow mechanical
movements of the disk heads.

Now it's cheap and easy to eliminate these movements if you have /lib
and /usr/lib on a 4GB memory stick.  Both are mounted ro because
system upgrades must go to the hidden on disk copies.  Since you won't
be able to unmount /lib and /usr/lib on a running system you have to
reboot without mounting the memory stick copies before upgrading.
That done, rsync both copies and remount the fast ones.  I'm thinking
of using different runlevels for this purpose but I still have to
investigate.

There is at least one more caveat in this approach: if you pull the
memory stick while it is mounted, everything can happen - most
probably a kernel panic or a complete system hang with unrecoverable
disk inconsistencies.

Comments welcome
  Siggy
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