[linux-lvm] RE: linux-lvm Digest, Vol 57, Issue 15

Peter Keller pkeller at globalphasing.com
Mon Dec 1 14:05:45 UTC 2008

Dear Antony,

On Mon, 1 Dec 2008, Antony MARTINEAU wrote:

> Hello Lars,
>  Andreas was whith us the last week  ;-)
> So I think to that xfs_freeze is no needed during a snapshot LVM2
> My backup Script do :
> system lvcreate --snapshot -n $snapname -L$snapsize /dev/$vg/$lv;
> So i think it is the best way to backup
> The last message about peter Keller worring me... You think to that XFS
> is not a filesystem that correspond whit database transactions???
> I think XFS is actually the best FS on all domains... can i use XFS for
> mysql database??

There is no reason to be worried about the compatability of MySQL and XFS 
filesystems. The word "correspond" is a bit of a "faux ami": it can mean 
very different things in French and English even though it is written the 
same way in both languages, which I think is the source of your confusion 

I used it in the (English) sense of "is equivalent to". I did not mean it in 
the sense of: "is compatible with". I was also using the word "transaction" 
in its narrow technical sense of a set of operations that take effect 
completely or not at all. If you read discussions about the XFS filesystem 
(or indeed any journaling filesystem), you will find that its operation is 
discussed using traditional database terminology (transactions, commits, 

The point that I was making is that some people seem to be misled by this 
into assuming that a a single transaction in a database is implemented using 
a single transaction on each of the underlying filesystems where data are 
being changed. If they implement a backup strategy that is based on this 
assumption, they will probably get backups that are less reliable than if 
they use the "FLUSH TABLES WITH READ LOCK" strategy.


Peter Keller                                     Tel.: +44 (0)1223 353033
Global Phasing Ltd.,                             Fax.: +44 (0)1223 366889
Sheraton House,
Castle Park,
Cambridge CB3 0AX
United Kingdom

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