Soft updates and power failure

Pete French pete at twisted.org.uk
Tue Feb 8 12:32:02 GMT 2005


> That's what I thought too...  But I was fiddling with some kernel 
> modules on a machine which caused it to spontaneously panic without 
> chance to sync disks (like power outages) and the disks were always 
> getting horribly messed up.  Once I added sync I've had no problems.

Now thats very interesting. Were the write caches enabled on the drives ?
I did some experiments dumping files and deliberately pulling the power
whilst the run was going. Softupdates always fsck'd clean, sync didn't.
That and the big performance hit made me never go for sync.

> Maybe it's different, but I can say that softupdate'd partitions are the 
> only ones I've ever had trouble with data corruption on, with surprise 
> reboots.

I might do some more experiments on 5.3 when I get the chance. I had
always relied on softupdates and no write caching being the most reliable
way I could run the drives - maybe that isn't true. Its kind of worrying
though, as the whole 'background fsck' on 5.3 is predicated on the idea that
the filesystem comes up clean with softupdates every time and only needs the
freespace checking and possibly recovering isn't it ?

-bat.




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