Ext3 has a stellar reputation for being a rock-solid filesystem

These new bdflush settings will cause kupdate to run every 0.6 seconds rather than every 5 seconds. In addition, they tell the kernel to flush a dirty buffer after 3 seconds rather than 30, the default. By flushing recently-modified data to disk more regularly, these write storms can be avoided. It's slightly less efficient to do things this way, since the kernel will have fewer opportunities to combine writes. But for a busy server, writes will happen more consistently, and interactive performance will be greatly improved.

The write cache

You may not know this, but most modern hard drives have something called a "write cache", used by the hard drive to collect pending write operations. By putting pending writes into a cache, the hard drive firmware can then reorder and group them so that they're written to disk in the fastest possible way. The write cache is generally considered to be a very good thing (read Linus' explanation and opinion of write caching in Resources).

Unfortunately, certain laptop hard drives now on the market have the dubious feature of ignoring any official ATA request to flush their write cache to disk. This isn't a wonderful design feature, although it has been allowed by the ATA spec up until recently. With these types of drives, there's no way for the kernel to guarantee that a particular block has actually been recorded to the disk platters. Although this sounds like a thorny problem, this particular issue by itself is probably not the cause of the data corruption problems that people have been experiencing.

However, it gets worse. Some modern laptop hard drives have an even nastier habit of throwing away their write cache whenever the system is rebooted or suspended. Obviously, if a hard drive has both of these problems, it's going to regularly corrupt data, and there's nothing that Linux can do to prevent it from doing so.

So, what's the solution? If you have a laptop, tread carefully. Back up all your important files before making any major change to your filesystems. If you experience data corruption problems that seem to fit the pattern of what I described above, particularly with ext3, then remember that it may be your laptop hard drive that's at fault. In that case, you may want to contact your laptop manufacturer and inquire about getting a replacement drive. Hopefully, in a few months time, these flaky hard drives will be pulled from the market and we'll never need to worry about this issue again.

LABEL=/                 /                       ext3    data=journal    1 0

LABEL=/boot             /boot                   ext3    data=journal    1 0