Messages in this thread | | | Date | Mon, 17 Mar 2008 10:23:10 -0700 (PDT) | From | david@lang ... | Subject | Re: [ANNOUNCE] Ramback: faster than a speeding bullet |
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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 never out of date.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)
David Lang
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