Re: Page Checksums

On Jan 8, 2012, at 5:25 PM, Simon Riggs wrote:
> On Mon, Dec 19, 2011 at 8:18 PM, Heikki Linnakangas
> <heikki.linnakangas@enterprisedb.com> wrote:
>
>> Double-writes would be a useful option also to reduce the size of WAL that
>> needs to be shipped in replication.
>>
>> Or you could just use a filesystem that does CRCs...
>
> Double writes would reduce the size of WAL and we discussed many times
> we want that.
>
> Using a filesystem that does CRCs is basically saying "let the
> filesystem cope". If that is an option, why not just turn full page
> writes off and let the filesystem cope?

I don't think that just because a filesystem CRC's that you can't have a torn write.

Filesystem CRCs very likely will not happen to data that's in the cache. For some users, that's a huge amount of data
toleave un-protected. 

Filesystem bugs do happen... though presumably most of those would be caught by the filesystem's CRC check... but you
neverknow! 
--
Jim C. Nasby, Database Architect                   jim@nasby.net
512.569.9461 (cell)                         http://jim.nasby.net