[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

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



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 :
FLUSH TABLES WITH READ LOCK;
system lvcreate --snapshot -n $snapname -L$snapsize /dev/$vg/$lv;
UNLOCK TABLES;
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 here.

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, etc.).

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.

Regards,
Peter.

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

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]