[Discuss] Backing up LVM partitions using snapshots

[markw at mohawksoft.com (markw at mohawksoft.com)]

> On 12/12/2011 10:39 PM, markw at mohawksoft.com wrote:
>> Why would that happen? That's what I don't understand. If you have a
>> mission critical failure of this sort, then you fall back to a previous
>> backup as your beginning and do a full backup at this point. You don't
>> ignore the failure and proceed business as usual.
>
> Follow closely:
>
> * Create file #1
> * Do full dump.  Contains file #1 data and directory metadata.
> * Create file #2.
> * Do incremental dump #1.  Contains file #1 directory metadata, file #2
> data and directory metadata.
> * Create file #3.
> * Make incremental dump #2.  Contains file #1 and #2 directory metadata,
> file #3 data and metadata.
> * Disaster strikes!  The server explodes in a ball of flame, or gets
> eaten by Gojira or something.  You replace the hardware and prepare for
> recovery.

OK.
> * Restore full dump to new server.  You now have file #1 complete.
> * Attempt to restore incremental dump #1 and find that it is unusable.

Using a block level store, an incremental backup is no different than a
full backup. It appears that you are thinking of using tape or something.
tape is dead. The backup medium is a combination of RAID and/or cloud.

With block level differential backup, you can effectively replicate a
volume with a minute amount of data.

There are many levels of disaster, if just the data volume is lost, then
it can be restored in full from any of the successful backups. if it is a
site level disaster, then you get your backup data from offsite or cloud.

I worked at a tape backup company years ago working with the QIC and DAT
formats. OMG what a disaster. Disk sectors are cheaper and more reliable.


>