Re: New server: SSD/RAID recommendations? - Mailing list pgsql-performance

From Graeme B. Bell
Subject Re: New server: SSD/RAID recommendations?
Date
Msg-id D0185D2A-A218-47D8-A798-2B92ABDCF4CF@skogoglandskap.no
Whole thread Raw
In response to Re: New server: SSD/RAID recommendations?  (Heikki Linnakangas <hlinnaka@iki.fi>)
Responses Re: New server: SSD/RAID recommendations?
List pgsql-performance
Cache flushing isn't an atomic operation though. Even if the ordering is right, you are likely to have a partial fsync
onthe disk when the lights go out - isn't your FS still corrupt? 

On 07 Jul 2015, at 21:53, Heikki Linnakangas <hlinnaka@iki.fi> wrote:

> On 07/07/2015 09:01 PM, Wes Vaske (wvaske) wrote:
>
> Right, to be precise, the problem isn't the drive lies about fsync(). It lies about FLUSH CACHE instead. Search &
replacefsync() with FLUSH CACHE, and the same question remains: When the drive breaks its promise wrt. FLUSH CACHE,
doesit nevertheless guarantee that the order the data is eventually flushed to disk is consistent with the order in
whichthe data and FLUSH CACHE were sent to the drive? That's an important distinction, because it makes the difference
between"the most recent data the application saved might be lost even though the FLUSH CACHE command returned" and
"yourfilesystem is corrupt". 
>



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