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Date:      Sun, 7 Jun 2009 08:53:19 +0200 (CEST)
From:      Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To:        Sergio de Almeida Lenzi <lenzi.sergio@gmail.com>
Cc:        freebsd-questions <questions@freebsd.org>
Subject:   Re: fsck on 1.5TB drive
Message-ID:  <alpine.BSF.2.00.0906070848390.97754@wojtek.tensor.gdynia.pl>
In-Reply-To: <1244340648.8936.7.camel@localhost>
References:  <56942.76.25.231.251.1244295367.squirrel@webmail.wcubed.net> <1244306366.5333.8.camel@localhost> <alpine.BSF.2.00.0906062312520.93574@wojtek.tensor.gdynia.pl> <1244340648.8936.7.camel@localhost>

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>
>
> You are right Puchar, but sometimes (2 in 100 on powerfailure) the
> filesystem
> gets corrupted (database files opened, and being extended)...  so
> when the fsck enters, the database get corrupted..

Filesystem will rather be not corrupted, but database file data.
Non-journalled UFS with softupdates guarrantes the right sequence of disk 
updates. For example it will not allocate just freed space until freeid 
inodes/blocks are not wrote back to disk.

As in your example - extended and written something, but will end unextended 
etc..

> by using zfs or journaling I never have anothter database problem....

This is sequence problem - for example you write to file A,B and C 
then it's a crash and you have file A and C written but not B.

I though that all this "famous" database systems like mysql already have 
mechanism for that. looks like not, or it should not get corrupted.




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