Re: [PATCH] Incremental backup: add backup profile to base backup

On Mon, Aug 18, 2014 at 04:05:07PM +0300, Heikki Linnakangas wrote:
> But more to the point, I thought the consensus was to use the
> highest LSN of all the blocks in the file, no? That's essentially
> free to calculate (if you have to read all the data anyway), and
> isn't vulnerable to collisions.

The highest-LSN approach allows you to read only the tail part of each
8k block.  Assuming 512-byte storage sector sizes, you only have to read
1/8 of the file.

Now, the problem is that you lose kernel prefetch, but maybe
posix_fadvise() would fix that problem.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + Everyone has their own god. +