Re: concurrent IO in postgres?

On Dec 23, 2010, at 13:22:32, Ben Chobot wrote:
>
> On Dec 23, 2010, at 11:58 AM, Andy wrote:
> >
> > Somewhat tangential to the current topics, I've heard that FusionIO
>uses
> > internal cache and hence is not crash-safe, and if the cache is turned
> > off performance will take a big hit. Is that your experience?
>
> It does use an internal cache, but it also has onboard battery power. The
> driver needs to put its house in order when restarting after an unclean
> shutdown, however, and that can take up to 30 minutes per card.

Sorry to intrude here, but I'd like to clarify the behavior of the
Fusion-io
devices. Unlike SSDs, we do not use an internal cache nor do we use
batteries.

(We *do* have a small internal FIFO (with capacitive hold-up) that is
100% guaranteed to be written to our persistent storage in the event of
unexpected power failure.)

When a write() to a Fusion-io device has been acknowledged, the data is
guaranteed to be stored safely. This is a strict requirement for any
enterprise-ready storage device.

Thanks,
John Cagle
Fusion-io, Inc.

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