Soft updates and power failure

Lee Brotherston lee at nerds.org.uk
Tue Feb 8 12:25:38 GMT 2005


Pete French wrote:
> Even with the cache it still guarantees the disc is not left in
> an inconsistent state doesnt it ? i.e. it only flushes the cache
> in consistent chunks to the drive.

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.

> Sync gives a *horrible* performance hit, and I don't believe that it makes the
> data any more likely to be consistent than running softupdates. Indeed
> when I did some experiments it was actually worse.

Maybe I'm an odd one off case, I'd not use sync on production machines 
agreed, but it seemed to fix what on the surface sounds like the same 
problem on my dev box.

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.

Thanks

   Lee




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