Better than POSIX? [LWN.net]

Better than POSIX?

Posted Mar 17, 2009 21:44 UTC (Tue) by man_ls (subscriber, #15091)
In reply to: Better than POSIX? by dlang
Parent article: Better than POSIX?

people were relatively happy with the ~5 second vulnerability window in ext3, but are getting bit by the ~60 second vulnerability window that ext4 defaulted to.

Well, if the 5-second window had left my systems vulnerable to data corruption (in the form of zero-length files) I know I would not have been happy. After all that 5-second window happens every 5 seconds, so you are virtually guaranteed to run into the problem if it exists, whatever the window size.

I remember my horror after finding out that XFS had lost my data, and I read about XFS devs hiding behind the standard "journalling filesystems only make guarantees about the metadata". "The metadata? fsck the metadata! What I want is my wretched data back!" Now it is all coming back in waves.

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Better than POSIX?

Posted Mar 18, 2009 2:40 UTC (Wed) by dlang (✭ supporter ✭, #313) [Link]

that 5 second window did leave you vulnerable to data corruption (in many ways). you just got lucky

Better than POSIX?

Posted Mar 18, 2009 4:12 UTC (Wed) by quotemstr (subscriber, #45331) [Link]

It wasn't really as bad as it sounds. ext3 also doesn't have delayed allocation. Someone on the Ubuntu bug list posted some testcases and really couldn't make ext3 fail at all. (ext4 fell flat.)

Better than POSIX?

Posted Mar 18, 2009 7:28 UTC (Wed) by man_ls (subscriber, #15091) [Link]

I know my data is vulnerable in many ways. I would just like the most common cases to be addressed. It is not luck. According to the discussions, everyone who has had a crash with (first) XFS or (now) ext4 is getting inconsistent states, while no heavy-duty ext3 users have reportedly seen this kind of corruption. Maybe others, yes, but no zero-length files -- which is the issue under discussion.