Re: New server: SSD/RAID recommendations?

Hi.

How would BBU cache help you if it lies about fsync? I suppose any RAID
controller removes data from BBU cache after it was fsynced by the drive.
As I know, there is no other "magic command" for drive to tell controller
that the data is safe now and can be removed from BBU cache.

Вт, 7 лип. 2015 11:59 Graeme B. Bell <graeme(dot)bell(at)nibio(dot)no> пише:

>
> Yikes. I would not be able to sleep tonight if it were not for the BBU
> cache in front of these disks...
>
> diskchecker.pl consistently reported several examples of corruption
> post-power-loss (usually 10 - 30 ) on unprotected M500s/M550s, so I think
> it's pretty much open to debate what types of madness and corruption you'll
> find if you look close enough.
>
> G
>
>
> On 07 Jul 2015, at 16:59, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>
> >
> > So it lies about fsync()... The next question is, does it nevertheless
> enforce the correct ordering of persisting fsync'd data? If you write to
> file A and fsync it, then write to another file B and fsync it too, is it
> guaranteed that if B is persisted, A is as well? Because if it isn't, you
> can end up with filesystem (or database) corruption anyway.
> >
> > - Heikki
>
>
>
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