> On Mon, 17 Mar 2008,
david@lang.hm wrote:
>
> >On Mon, 17 Mar 2008, Daniel Phillips wrote:
> >
> >>On Sunday 16 March 2008 23:49,
david@lang.hm wrote:
> >>>>Mirroring on the other hand, makes a realtime copy of a volume, that is
> >>>>never out of date.
> >>>
> >>>so just mirror to a local disk array then.
> >>
> >>Great idea. Except that the disk array has millisecond level latency,
> >>when what we trying to achieve is microsecond level latency.
> >>
> >>>a local disk array has more write bandwidth than a network connection to
> >>>a
> >>>remote machine, so if you can mirror to a remote machine you can mirror
> >>>to
> >>>a local disk array.
> >>
> >>So you could potentially connect to a _huge_ disk array and write deltas
> >>to it. The disk array would have to support roughly 3 Gbytes/second of
> >>write bandwidth to keep up with the Violin ramdisk. Doable, but you are
> >>now in the serious heavy iron zone.
> >
> >your network will do less then 1 Gbit/sec, so to mirror in real-time (what
> >you claim is trivial) you would need at least 24 network connections in
> >parallel. that's a LOT harder to setup then a high performance disk array.
>
> by the way, the only way to get this much bandwideth between two machines
> is to directly connect PCI-e/16 card slots togeather. this is definantly
> not commodity hardware anymore (if it's even possible, PCI-e has some very
> short distance limitations)
