On Mon, 17 Mar 2008, Daniel Phillips wrote:
On Sunday 16 March 2008 23:49, david@xxxxxxx 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never out of date.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.