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List:       linux-ext4
Subject:    lifetime_write_kbytes isn't preserved during unclean shutdown
From:       Nebojsa Trpkovic <trx.lists () gmail ! com>
Date:       2010-06-27 16:56:07
Message-ID: 4C2782A7.7040301 () gmail ! com
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I've noticed that lifetime_write_kbytes isn't preserved during unclean
shutdown.
At least on my Intel X25-V, but I guess it's ext4's issue, not Intel's
one. :)

lifetime_write_kbytes constantly grow while using filesystem. If
computer is rebooted regulary with clean unmount, next time it boots
lifetime_write_kbytes will continue incrementing counter and everything
seems to work right.

Then again, if there was unclean shutdown/reboot, lifetime_write_kbytes
will be reset to value of last clean unmount. Example:

lifetime_write_kbytes 18 GB
lifetime_write_kbytes 20 GB
lifetime_write_kbytes 22 GB
clean reboot
lifetime_write_kbytes 22 GB
lifetime_write_kbytes 24 GB
lifetime_write_kbytes 26 GB
unclean reboot (reboot switch/power failure/whatever)
lifetime_write_kbytes 22 GB
...

I guess that /sys takes value written in filesystem itself and increment
it during system operation, but writes back new lifetime_write_kbytes
value to filesystem just on clean unmount.
It seems it would not hurt to write periodicly, maybe not too often - 10
minutes or so, intermidiate lifetime_write_kbytes value to filesystem
and avoid unnecessary lost of lifetime_writes on unclean reboot.

Nebojsa Trpkovic

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