On Sat, 29 Aug 2009, Pavel Machek wrote:
for flash drives the danger is very straightforward (although even then
you have to note that it depends heavily on the firmware of the device,
some will loose lots of data, some won't loose any)
I have not seen one that works :-(.
so let's get broader testing (including testing the SSDs as well as the
thumb drives)
you are generalizing that since you have lost data on flash drives, all
flash drives are dangerous.
Do the flash manufacturers claim they do not cause collateral damage
during powerfail? If not, they probably are dangerous.
I think that every single one of them will tell you to not unplug the
drive while writing to it. in fact, I'll bet they all tell you to not
unplug the drive without unmounting ('ejecting') it at the OS level.
Anyway, you wanted a test, and one is attached. It normally takes like
4 unplugs to uncover problems.
Ok, help me understand this.
I copy these two files to a system, change them to point at the correct
device, run them and unplug the drive while it's running.
when I plug the device back in, how do I tell if it lost something
unexpected? since you are writing from urandom I have no idea what data
_should_ be on the drive, so how can I detect that a data block has been
corrupted?
David Lang
#!/bin/bash
#
# Copyright 2008 Pavel Machek <pavel@xxxxxxx>, GPLv2
#
# vfat is broken with filesize=0
#
#
if [ .$MOUNTOPTS = . ]; then
# ext3 is needed, or you need to disable caches using hdparm.
# odirsync is needed, else modify fstest.worker to fsync the directory.
MOUNTOPTS="-o dirsync"
fi
if [ .$BDEV = . ]; then
# BDEV=/dev/sdb3
BDEV=/dev/nd0
fi
export FILESIZE=4000
export NUMFILES=4000
waitforcard() {
umount /mnt
echo Waiting for card:
while ! mount $BDEV $MOUNTOPTS /mnt 2> /dev/null; do
echo -n .
sleep 1
done
# hdparm -W0 $BDEV
echo
}
mkdir delme.fstest
cd delme.fstest
waitforcard
rm tmp.* final.* /mnt/tmp.* /mnt/final.*
while true; do
../fstest.work
echo
waitforcard
echo Testing: fsck....
umount /mnt
fsck -fy $BDEV
echo Testing....
waitforcard
for A in final.*; do
echo -n $A " "
cmp $A /mnt/$A || exit
done
echo
done
#!/bin/bash
#
# Copyright 2008 Pavel Machek <pavel@xxxxxxx>, GPLv2
#
echo "Writing test files: "
for A in `seq $NUMFILES`; do
echo -n $A " "
rm final.$A
cat /dev/urandom | head -c $FILESIZE > tmp.$A
dd conv=fsync if=tmp.$A of=/mnt/final.$A 2> /dev/zero || exit
# cat /mnt/final.$A > /dev/null || exit
# sync should not be needed, as dd asks for fsync
# sync
mv tmp.$A final.$A
done
