On 12/15/2010 04:46 PM, luvar@xxxxxxxxxxxx wrote:
First of all, I would like to thanks for answers.
One more question and some reply in text.
After making ssd disc a cache for some partition, there is possibility to detach cache. What should I do to "erase" (trim) whole disk for another benchmarking? I think that "dd if=/dev/zero of=/dev/sdx" wouldnt be right command.
Yeah, one nifty thing is you can disable caching on a mounted, in use
filesystem (and reenable it provided you invalidate the cache somehow).
Hdparm can send a trim, but it can't do the whole disk at once, you've
got to script it. I wrote one awhile back, this is what I use:
#!/bin/bash
DEV=$1
if [ ! -b "$DEV" ]; then
echo "Can't open $DEV"
exit 1
fi
SECTORS=`hdparm -I "$DEV"|awk '/LBA48/ { print $5 }'`
OFFSET=0
echo "$DEV has $SECTORS sectors:"
while (($SECTORS)); do
i=$(( $SECTORS > 65535 ? 65535 : $SECTORS ))
echo "wiping $i sectors at offset $OFFSET"
hdparm --please-destroy-my-drive \
--trim-sector-ranges $OFFSET:$i $DEV
SECTORS=$(($SECTORS - $i))
OFFSET=$(($OFFSET + $i))
done
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