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Old 08-19-2010, 07:03 PM
Mick
 
Default Incomplete mysql backup

I use mysqldump to back up a database from a development environment and
upload it to a production environment.

A couple of days ago I was surprised to see that I was getting errors as soon
as I uploaded the backed up database to the production machine! I repeated
the backup (more in disbelief than anything else) but the error remained.

I spent a few minutes looking around and scratching my head as to what was
amiss with it, until eventually I noticed that the recent backup was smaller
than the previous version (it should have been bigger due to extra data that
has accumulated in the database). I had another final go in running the same
good ol' mysqldump command and this time it worked. The backup was a
reasonable size and the upload restored the application in the production
environment in a good working order.

Is there a right and a wrong way of backing up mysql? Did I do something
wrong? How should one verify that a back up is sound? (Imagine trying to
restore from that incomplete backup!)
--
Regards,
Mick
 
Old 08-20-2010, 04:58 AM
kashani
 
Default Incomplete mysql backup

On 8/19/2010 12:03 PM, Mick wrote:

I use mysqldump to back up a database from a development environment and
upload it to a production environment.

A couple of days ago I was surprised to see that I was getting errors as soon
as I uploaded the backed up database to the production machine! I repeated
the backup (more in disbelief than anything else) but the error remained.

I spent a few minutes looking around and scratching my head as to what was
amiss with it, until eventually I noticed that the recent backup was smaller
than the previous version (it should have been bigger due to extra data that
has accumulated in the database). I had another final go in running the same
good ol' mysqldump command and this time it worked. The backup was a
reasonable size and the upload restored the application in the production
environment in a good working order.

Is there a right and a wrong way of backing up mysql? Did I do something
wrong? How should one verify that a back up is sound? (Imagine trying to
restore from that incomplete backup!)


mysqldump -A --single-transaction

That's usually the best way to backup if you have a single machine.
Without --single-transaction you may or may not get a proper backup when
using Innodb tables on a busy server.


However in a busy production environment it's usually best to use a
slave to do backups. Bringing LVM snapshots into the mix is also useful,
but you must lock and flush Mysql in order to get a correct snapshot
which makes it only an option on the slave.


kashani
 
Old 08-20-2010, 07:29 PM
Mick
 
Default Incomplete mysql backup

On Friday 20 August 2010 05:58:49 kashani wrote:
> On 8/19/2010 12:03 PM, Mick wrote:
> > I use mysqldump to back up a database from a development environment and
> > upload it to a production environment.
> >
> > A couple of days ago I was surprised to see that I was getting errors as
> > soon as I uploaded the backed up database to the production machine! I
> > repeated the backup (more in disbelief than anything else) but the error
> > remained.
> >
> > I spent a few minutes looking around and scratching my head as to what
> > was amiss with it, until eventually I noticed that the recent backup was
> > smaller than the previous version (it should have been bigger due to
> > extra data that has accumulated in the database). I had another final
> > go in running the same good ol' mysqldump command and this time it
> > worked. The backup was a reasonable size and the upload restored the
> > application in the production environment in a good working order.
> >
> > Is there a right and a wrong way of backing up mysql? Did I do something
> > wrong? How should one verify that a back up is sound? (Imagine trying
> > to restore from that incomplete backup!)
>
> mysqldump -A --single-transaction
>
> That's usually the best way to backup if you have a single machine.
> Without --single-transaction you may or may not get a proper backup when
> using Innodb tables on a busy server.

Yes, it is a single machine (the one with the dev't environment) but it has a
dozen databases on it, so the -A option is not appropriate.

The engine is the default MyISAM and this made me think if it is the reason
that two backups in a row were incomplete. Should I be converting all tables
to Innodb?

The production server is separate.

> However in a busy production environment it's usually best to use a
> slave to do backups. Bringing LVM snapshots into the mix is also useful,
> but you must lock and flush Mysql in order to get a correct snapshot
> which makes it only an option on the slave.

Thanks kashani, I'll try the --single-transaction and see what I get. I
hadn't had such a hiccup for years now, so it came as a surprise to me. I was
thinking that I should perhaps use --lock-tables, because the --single-
transaction states:

"This option issues a BEGIN SQL statement before dumping data from the server"

and I don't really understand how this will affect the backup ... ?
--
Regards,
Mick
 

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