980Avoiding writes to USB flash disk
- Aug 31, 2004Hi,
For those of you using the NSLU2 with only a flash
disk, you may be interested in this. I've been
looking into minimizing writes to prolong the life
of the flash disk. This is probably not a big deal,
but why burn out something sooner than necessary?
I discovered that simply accessing a file (reading) can
cause the OS to update that file's access time. This
causes a write to the filesystem even though you didn't
intend it. You could mount the filesystem read-only,
but that becomes inconvienent.
There are a couple of ways you can prevent this, one
is on a per-file basis and the other is filesystem wide.
To turn off the updating of the access times, mount
the filesystem with "noatime". I just tested this
with a vfat filesystem and it seemed to work.
If you already have your vfat filesystem mounted (e.g.
with a single usb flash drive like me), you can type this
Note: (first check the output of the mount or df commands to
make sure your devices are the same).
# mount -t vfat -o remount,noatime /dev/sdb1 /share/flash/data
If you want to verify that this is working (to
check i/o stats), type the following command:
# cat /proc/stat
This means there were 953 total I/Os to my device
(I assume 8,1 means /dev/sdb1). There were 949 reads
and 4 writes.
If you run the cat command in a loop in one window and do activity
in another, you can play around and get feedback on what you
are doing and how it affects the filesystem.