On Thu, 6 Jan 2005 22:12:38 -0700 Collins Richey <[EMAIL PROTECTED]> wrote:
> That's encouraging to hear. > > My only 3 experiences with reiserfs (1x late 2.4, 2x on 2.6, never > again in this lifetime) led to total fs corruption after a powerfail. Power failure is completely different to a crash! Unlike in case of a crash, internal disk buffers are not flushed in case of a power failure. This means, that *every* journaling FS can fail completely. If everything works well, it is pure luck. In common setups, journaling filesystems do *not* protect against damage from power loss, not even those that do full data journaling. This is something that many people are not aware of. The reason is, that modern disks reorder write operations, meaning that data arrives on the disk in a different order than the filesystem expects. This is very dangerous. There are several solutions: 1) disable write caching via hdparm -W (This can severly lower write performance and even shorten a disk's lifetime) 2) use an UPS 3) use kernel 2.6.9 or later, which supports so called "write barriers", at least in ReiserFS and ext3. Run "dmesg | grep flushes", you should see something like hda: cache flushes supported hde: cache flushes not supported Here hda suppports barriers, hde doesn't. Unless you use one of those solutions, every journaling fs can, and some day will, experience corruption on power failure. There is a web page where some test results are displayed. They managed to damage both ReiserFS and ext3 beyond recovery with only 3-4 power failures. Unfortunately I lost the URL... Regards -- [email protected] mailing list
