[CentOS] block level changes at the file system level?

[Rainer Duffner]

Am 03.07.2014 um 21:19 schrieb John R Pierce <pierce at hogranch.com>:

> On 7/2/2014 12:53 PM, Lists wrote:
>> I'm trying to streamline a backup system using ZFS. In our situation,
>> we're writing pg_dump files repeatedly, each file being highly similar
>> to the previous file. Is there a file system (EG: ext4? xfs?) that, when
>> re-writing a similar file, will write only the changed blocks and not
>> rewrite the entire file to a new set of blocks?
>> 
>> Assume that we're writing a 500 MB file with only 100 KB of changes.
>> Other than a utility like diff, is there a file system that would only
>> write 100KB and not 500 MB of data? In concept, this would work
>> similarly to using the 'diff' utility...
> 
> you do realize, adding/removing or even changing the length of a single 
> line in a block of that pg_dump file will change every block after it as 
> the data will be offset ?
> 
> may I suggest that instead of pg_dump, you use pg_basebackup and WAL 
> archiving...  this is the best way to do delta backups of a sql database 
> server.
> 
> 


Additionally, I’d be extremely careful with ZFS dedup.

It uses much more memory than „normal“ ZFS and tends to consume more I/Os, too.