bgfsck in 6.1

bgfsck in 6.1

Post by bas » Tue, 06 Jun 2006 22:56:20


Back in Oct 2005 I followed the recommendation of a few people in this
group and turned off bgfsck because there were surprising
inconsistencies in the file system. I'm upgrading to 6.1 now and
wonder if it is safe to turn bgfsck back on and trust it to find and
fix problems.
 
 
 

bgfsck in 6.1

Post by Kris Kenna » Tue, 06 Jun 2006 23:38:47


If your system is panicking, bg fsck is never going to be 100% safe.
If you're just losing power, it might be OK.

Kris

 
 
 

bgfsck in 6.1

Post by conrad » Tue, 06 Jun 2006 23:49:44

In article < XXXX@XXXXX.COM >,



Works fine for me, and it sure beats sitting and waiting for a foreground
fsck to complete. :-)

--
Conrad J. Sabatier < XXXX@XXXXX.COM > -- "In Unix veritas"
 
 
 

bgfsck in 6.1

Post by bas » Wed, 07 Jun 2006 12:29:15


Hmm, I guess "might be OK" means leave it off.

By the way, what happens is not system panics, but for example, last
week I was away and tech support tried to install some kind of Win or
NetWare upgrade on my FBSD box. They got confuse and turned it off --
the perils of having the only non-Win box in the building.
 
 
 

bgfsck in 6.1

Post by bas » Wed, 07 Jun 2006 12:36:18


Last year, I thought it worked for me too ... until it didn't. Just
wondering if the folks who knew about the dangers last year know if it
is safer now.
 
 
 

bgfsck in 6.1

Post by Kris Kenna » Thu, 08 Jun 2006 02:43:59


I turn it off on all of my machines, but that's mostly because they
panic a lot from the stress testing I do.


One of the problems with bg fsck is that its fundamental premise is
violated by modern disk hardware. Modern drives have a write cache
that allows them to speed up I/O by acknowledging the write as
"complete" to the OS when it's only in volatile storage. In the event
of a power failure the drive just dumps the cache, so the writes are
lost and the on-disk data may be inconsistent.

You can "fix" this by turning off the write cache, but your
performance will be in the toilet.

Kris