| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Marco Nenciarini <marco(dot)nenciarini(at)2ndquadrant(dot)it>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PATCH] Incremental backup: add backup profile to base backup |
| Date: | 2014-08-20 23:24:20 |
| Message-ID: | 20140820232420.GD17822@momjian.us |
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| Lists: | pgsql-hackers |
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(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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