Messages in this thread | | | Date | Mon, 17 Mar 2008 18:30:01 +0100 | From | Willy Tarreau <> | Subject | Re: [ANNOUNCE] Ramback: faster than a speeding bullet |
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On Mon, Mar 17, 2008 at 10:23:10AM -0700, david@lang.hm wrote: > 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never out of date.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)
You can do that with 3 10GE NICS, though in practise that's not easy.
Willy
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