Re: [BackupPC-users] Can I disable file pooling?

On 8/27/2010 10:03 AM, Jeffrey J. Kosowsky wrote:
> junk wrote at about 08:24:49 -0400 on Friday, August 27, 2010:
>   >  Hi everyone,
>   >
>   >  I'm wondering if there's a way to disable pooling (i.e. file copy
>   >  instead of a hard link)?  In other words, can I disable de-duplication?
>   >
>   >  I ask because in some circumstances, I might prefer to consume more
>   >  space in order to de-risk against the possibility of a single bit
>   >  "flipping" and corrupting all instances of a hard-linked file.
>   >
>   >  Thanks for your help
>   >  :-)
>   >
>
> I think you would be much better up backing up the pool or running
> multiple copies of BackupPC. I don't know the exact statistics, but I
> know that "single bit flips" are in general *way* less likely than disk
> failures or file system corruptions  that would affect the entire pool
> whether de-duped or not.

I have to agree with this - in practice you just don't see uncorrected 
disk bit errors but drives do fail moderately often in ways that lose 
the whole filesystem at once.   On the other hand, RAM errors can cause 
subtle corruption but it's not likely to go unnoticed for long.  If you 
are concerned about any of this (or site-level disasters), set up a 2nd 
server to make independent copies or do disk-image copies of your pool 
filesystem to rotate offsite regularly.

In any case, the way backuppc works, if you don't enable the checksum 
seed option, each full rsync run will compare the original against the 
existing copy - and if any difference is detected you get a new pool 
entry.  Even if you do enable the checksum seeding, some percentage of 
the runs still do the comparison to make sure your pool copy is good.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com



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