[GRLUG] Flash for /

[Michael Mol]

I've been looking at a solid-state disk of some sort as / for my next
computer, so I thought I'd share my observations and get some
comments.

Solid-state disks have a minuscule seek time compared to magnetic
disks.  For most systems, this should speed up bootup and initial
loading of apps, and reduce app load times if your disk cache was
flushed.  This is my primary motivation for using a SSD as /.

There are two types of SSD technology, Single-Level Cell (SLC) and
Multi-Level Cell (MLC).  MLC drives are typically cheaper, but they're
also slower and less reliable (they have a lower write-cycle
lifetime).  Most flash devices, be they SSD disks, memory cards or USB
thumb drives, don't list whether they're SLC or MLC.

You may not need as much disk as you think.  A fresh install of Ubuntu
takes less than 3GB.  My crufty desktop computer running Ubuntu
upgrades via dist-upgrade for acouple years, still only uses about 5GB
on /.  You may only need a 4GB or 8GB drive, if you can put /home on a
different drive. (In my case, /home has been a separate drive for
years.)

When you're talking about drive sizes only as large as 8GB, you can
forget about the fancy 2.5" SSDs.  Those typically don't get that
small.  Instead, look at 266X and 300X CompactFlash drives as sold for
high-end cameras, where you can get transfer rates of 40MB/s or more.
They're not as fast as the 80MB/s SATA2 SSDs, but they're a heck of a
lot cheaper.  Stay away from SDHC cards.  Sure, they can cheaply get
you into the 16-32GB range, but the SDHC spec lists a maximum transfer
rate of 6MB/s.  I don't have any performance numbers on thumb drives.
Sure, USB2 is supposed to support 400MB/s, but, as with SLC SATA
disks, actual performance will be dependent on the innards of the
drive.

Another thing to think about is wear-leveling.  Unfortunately, I
haven't seen wear-leveling listed in the specs for any of the flash
products I've looked into.

-- 
:wq