Re: Filesystem corruption

[David Masover <ninja@slaphack.com>]

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On Wednesday 30 May 2007 12:22:17 devsk wrote:

> I have used R4 for a year now and I have had to reset my PC,
> troubleshooting problems with vmware/mythtv/cisco vpn client/nvidia, so
> many times that its not even funny! And R4 didn't give me any problems even
> once. It boots right up, without any files lost and consistent FS as a
> subsequent livecd boot and fsck proved it everytime.

That happened to me for maybe a year or so, I'm not sure. Then, slowly, I 
started to get problems. The machine crashing due to some nvidia bug -- or 
even a reiser-specific oops or something -- then I'd have to fsck it, which 
would take an hour or more, then I'd boot, and apparently no problems.

Only, recently, these fsck-a-thons started happening more and more often, and 
I started to lose random files. They'd just be silently truncated to 0 bytes. 
And not files I was writing a lot -- I'm talking about things 
like /bin/mount.

Now, maybe it's an amd64-specific bug. Or (somehow) a dmraid-specific bug, or 
a dont_load_bitmap bug. (Who can blame me; without dont_load_bitmap, it takes 
at least 30 seconds, maybe a minute to mount.) Could even be, somehow, a 
Gentoo-specific bug. Could be a 350-gig-partition bug, or even a bug of the 
it-hates-me variety. (My server ran Reiser4 for awhile longer, with no 
problems, but I wasn't about to take chances there.)

But, I switched a friend over to Ubuntu, and he had the same kind of problems. 
In fact, he had them first (I thought it was his computer, for awhile).

Finally, we switched to stock Ubuntu kernels and XFS, me on dmraid, him on 
normal linux raid5 (md), and we now have no problems. It's even faster -- the 
biggest gain for Reiser4 was /usr/portage, which doesn't exist on Ubuntu.

> If I did that to ext 
> or xfs, I would have lost big time.

Well, I'm on XFS on my desktop now, and ext3 on my server. No problems at all 
so far. Also much faster, because my desktop now has a repacker (xfs_fsr).

> I hope people don't leave this good piece of code to rot!!

Me too, but you know, I can no longer afford to spend a few hours running fsck 
for no apparent reason. I no longer have a machine that can do anything but 
just work.

The killer feature of Reiser4, as implemented, is small file performance that 
makes ReiserFSv3 weep, and v3 makes XFS weep. All the other stuff we were 
promised is either planned for a later release (repacker, pseudofiles, 
transaction API) or barely working (cryptocompress).

And on just about any setup I work on today, small file performance is a small 
enough priority that even the slightest hint of instability is a 
deal-breaker. Enough people feel the same way that ext3 is still widely used. 
And if it's ever really crucial, there's reiserfs3.

So, you can blame it on my hardware, or on not getting kernel inclusion, or 
anything you want, but the only place I still use Reiser4 is on the 
gameserver at our LAN party, and we're thinking of moving that to something 
like ext3 or xfs, just so we don't need custom kernels. And after all, that's 
a gameserver, it's not like the filesystem is the bottleneck anyway.

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