Search Postgresql Archives

Re: Aw: Re: pg_dump include/exclude data, was: verify checksums / CREATE DATABASE

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 6/11/19 11:15 AM, Karsten Hilbert wrote:
The problem I hope to protect against with this approach: the
CREATE DATABASE might untaint corrupted data from a bad disk
block into a good disk block virtue of doing a file level
copy.

I hope my reasoning isn't going astray.

As I understand it checksums are done on the page level using a hash(for
details: https://doxygen.postgresql.org/checksum__impl_8h_source.html).
I am not sure how a page could get un-corrupted by virtue of a file copy.

Ah, no, I did not explain myself well.

Let's assume a corrupted, bad (but readable at the hardware
level) disk block B. A filesystem level copy (as in CREATE
DATABASE) would successfully read that disk block B and
copy the corrupted content into a good disk block G elsewhere
on the disk. Verifying the checksum of the page sitting on
block B before doing the database cloning would
reveal the corruption before it got cloned.

Does that make sense ?

Yes.


Karsten



--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx





[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]

  Powered by Linux