| Re: Re: vzmigrate standby mode [message #42745 is a reply to message #42743] |
Wed, 18 May 2011 11:49   |
Tim Small
Messages: 24
Registered: April 2011
|
Junior Member |
|
|
On 18/05/11 12:30, Tim Small wrote:
>
> We use a hacked version of mylvmbackup to backup an entire container.
> Each container lives on its own logical volume, and the process calls
> into the logical volume to ask the database (mysql in this case) to make
> its data-on-disk consistent. At this point, and LVM snapshot is taken,
> then mysql is told it can carry on writing to disk. The LVM snapshot is
> then fscked and mounted on a different mountpoint, once mounted, the
> contents are rsynced to the standby machine, and the lvm snapshot is
> removed.
>
I should add that this is done at a relatively quiet time on the server
(if it's a server with lots of writes), as it has the side effect of
turning a single write on the containers storage into two writes and a
read (plus associated disk seeks) whilst the LVM snapshot exists.
Whilst the lvm snapshot is being created (< 1 second), writes to the
database block (reads continue as normal, however), then continue once
mysql gets the UNLOCK TABLES command. I don't know if there is
equivalent functionality available in other databases such as PostgreSQL
etc.
Cheers,
Tim.
--
South East Open Source Solutions Limited
Registered in England and Wales with company number 06134732.
Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ
VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309
|
|
|
|
OpenVZ Forum
Members
Search
Help
Register
Login
Home
