Re: SOLVED: Recover from LVM errors? (Was: Re: [gentoo-user] Help - system reboots while compiling)

[Boyd Stephen Smith Jr.]

On Wednesday 28 March 2007, "Jeff Rollin" <jeff.rollin@×××××.com> wrote 
about 'SOLVED: Recover from LVM errors? (Was: Re: [gentoo-user] Help - 
system reboots while compiling)':
> Ignore the following if you don't like minirants.
(My reply probably needs the same disclaimer.)

> 1. Frankly, I'm not impressed with Linux in this case*. /var is not a
> "mission critical" filesystem in the sense that if it contains errors,
> it can still be mounted and the errors don't necessarily mean the
> system won't come up.

By that definition, no filesystem I can think of is "mission critial", they 
will all withstand some damage and still let your system come up.  /var is 
*at least* as important as /usr -- I can easily recover the contents 
of /usr in case of critical failure, but reconstructing /var is damn near 
impossible.  Also, /usr can generally be very useful with just r/o access, 
while /var needs to be r/w to fill it's role.

Also, forcing a mount of a damaged filesystem is asking for trouble.  
Dangling inodes (or similar) can cause cascading failure; at best some 
processes will read garbage and crash (or, ideally, "magically" recover) 
at worst good data on the disk will be overwritten with bad. File locks on 
a damaged filesystem are meaningless since two files (not simply two 
dirents like with a hard link, but two unrelated files) might share disk 
sectors.

The system should definitely refuse to mount damaged file systems by 
default or *at the very least* mount them read-only.  I wouldn't mind and 
interactive prompt to force mounting a damaged filesystem, but I'd need a 
way to turn that off for unattended systems.

-- 
Boyd Stephen Smith Jr.                     ,= ,-_-. =. 
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