Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-14 Thread Peter J. Holzer
On 2018-01-10 11:39:21 -0800, Andres Freund wrote: > On 2018-01-09 20:51:17 -0500, Stephen Frost wrote: > > * Andreas Joseph Krogh (andr...@visena.com) wrote: > > > Aha, so enabling CRC causes hint-bits to be written causing extra > > > WAL-logging, > > > which woudn't be the case without CRC ena

Sv: Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-10 Thread Andreas Joseph Krogh
På onsdag 10. januar 2018 kl. 22:36:42, skrev Jeff Janes mailto:jeff.ja...@gmail.com>>: On Wed, Jan 10, 2018 at 12:23 PM, Thomas Poty mailto:thomas.p...@gmail.com>> wrote: Hello, A question seems to be, according to me, important : How a corruption, detected thanks to data-checksums, is fixed?  

Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-10 Thread Jeff Janes
On Wed, Jan 10, 2018 at 12:23 PM, Thomas Poty wrote: > Hello, > A question seems to be, according to me, important : > How a corruption, detected thanks to data-checksums, is fixed? > Take two full cold backups of the current mess you have, including the executables, and lock one of them away wh

Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-10 Thread Thomas Poty
Hello, A question seems to be, according to me, important : How a corruption, detected thanks to data-checksums, is fixed? Thank you, Thomas Le 10 janv. 2018 20:39, "Andres Freund" a écrit : > On 2018-01-09 20:51:17 -0500, Stephen Frost wrote: > > Greetings, > > > > * Andreas Joseph Krogh (andr

Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-10 Thread Andres Freund
On 2018-01-09 20:51:17 -0500, Stephen Frost wrote: > Greetings, > > * Andreas Joseph Krogh (andr...@visena.com) wrote: > > Aha, so enabling CRC causes hint-bits to be written causing extra > > WAL-logging, > > which woudn't be the case without CRC enabled? > > Thanks for pointing that out. > >

Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Andres Freund
On 2018-01-10 01:31:58 +0100, Andreas Joseph Krogh wrote: > På onsdag 10. januar 2018 kl. 01:01:26, skrev Andres Freund > >: > On 2018-01-10 00:25:08 +0100, Andreas Joseph Krogh wrote: > > But SIMD-instructions are also HW-accellerated by modern CPUs IIUC? > > Sure.

Re: Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Stephen Frost
Greetings, * Andreas Joseph Krogh (andr...@visena.com) wrote: > Aha, so enabling CRC causes hint-bits to be written causing extra > WAL-logging, > which woudn't be the case without CRC enabled? > Thanks for pointing that out. Yes, having checksums enabled forces logging of hint bits. You can e

Sv: Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Andreas Joseph Krogh
På onsdag 10. januar 2018 kl. 01:01:26, skrev Andres Freund mailto:and...@anarazel.de>>: On 2018-01-10 00:25:08 +0100, Andreas Joseph Krogh wrote: > På tirsdag 09. januar 2018 kl. 23:42:45, skrev Rob Sargent < > robjsarg...@gmail.com >: >   > >    On 01/09/2018 03

Re: Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Andres Freund
On 2018-01-10 00:25:08 +0100, Andreas Joseph Krogh wrote: > På tirsdag 09. januar 2018 kl. 23:42:45, skrev Rob Sargent < > robjsarg...@gmail.com >: >   > >   On 01/09/2018 03:30 PM, Andreas Joseph Krogh wrote: > På tirsdag 09. januar 2018 kl. 23:06:06, skrev Andres F

Sv: Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Andreas Joseph Krogh
På tirsdag 09. januar 2018 kl. 23:42:45, skrev Rob Sargent < robjsarg...@gmail.com >:     On 01/09/2018 03:30 PM, Andreas Joseph Krogh wrote: På tirsdag 09. januar 2018 kl. 23:06:06, skrev Andres Freund < and...@anarazel.de >: Hi, On 2018

Re: Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Rob Sargent
On 01/09/2018 03:30 PM, Andreas Joseph Krogh wrote: På tirsdag 09. januar 2018 kl. 23:06:06, skrev Andres Freund mailto:and...@anarazel.de>>: Hi, On 2018-01-09 21:47:17 +0100, Andreas Joseph Krogh wrote: > Does PG use HW-accellerated crc if CPU supports it[1]? Yes we do, for

Sv: Re: Sv: Re: data-checksums

2018-01-09 Thread Andreas Joseph Krogh
På tirsdag 09. januar 2018 kl. 23:06:06, skrev Andres Freund mailto:and...@anarazel.de>>: Hi, On 2018-01-09 21:47:17 +0100, Andreas Joseph Krogh wrote: > Does PG use HW-accellerated crc if CPU supports it[1]? Yes we do, for WAL checksums. The page checksums are a different algorithm though, o

Re: Sv: Re: data-checksums

2018-01-09 Thread Andres Freund
Hi, On 2018-01-09 21:47:17 +0100, Andreas Joseph Krogh wrote: > Does PG use HW-accellerated crc if CPU supports it[1]? Yes we do, for WAL checksums. The page checksums are a different algorithm though, one which has the advantage of being SIMD compatible. The checksum computations have some impa

Sv: Re: data-checksums

2018-01-09 Thread Andreas Joseph Krogh
På tirsdag 09. januar 2018 kl. 21:37:16, skrev Joshua D. Drake < j...@commandprompt.com >: On 01/09/2018 12:22 PM, Andres Freund wrote: > On 2018-01-09 20:04:04 +0100, Rakesh Kumar wrote: I also would like to believe that the hit is small, but when PG off