| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Ivan Kartyshov <i(dot)kartyshov(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [Patch] Checksums for SLRU files |
| Date: | 2018-08-02 01:20:22 |
| Message-ID: | 20180802012022.mciwun4kszjsnmcf@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2018-Aug-02, Thomas Munro wrote:
> PostgreSQL only requires atomic writes of 512 bytes (see
> PG_CONTROL_MAX_SAFE_SIZE), the traditional sector size for disks made
> approximately 1980-2010, though as far as I know spinning disks made
> this decade use 4KB sectors, and for SSDs there is more variation. I
> suppose the theory for torn SLRU page safety today is that the
> existing SLRU users all have fully independent values that don't cross
> sector boundaries, so torn writes can't corrupt them.
Hmm, I wonder if this is true for multixact/members. I think it's not
true for either 4kB sectors nor for 512 byte sectors.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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