RE: Sizing bandwidth for Disaster Tolerant cluster inter site links
From: Main, Kerry (kerry.main_at_hp.com)
Date: Fri, 27 Feb 2004 08:57:35 -0500
> -----Original Message-----
> From: Andrew Rycroft [mailto:email@example.com]
> Sent: February 27, 2004 7:37 AM
> To: Info-VAX@Mvb.Saic.Com
> Subject: Sizing bandwidth for Disaster Tolerant cluster inter
> site links
> I would really appreciate if anybody can advise me here.
> We plan to implement a disaster tolerant cluster with
> OpenVMS. I have now been asked to size the require bandwidth
> to meet the application needs. The 2 sites are about 10km
> apart, and we can put in a managed fibre link, but it is very
> expensive. We have 2 disks that we intend to volume shadow
> across the 2 sites. The average IO rate on the one disk is
> 100 IO/sec, and on the other 50 IO/Sec.
> I have seen various presentations where OPenVMS can be
> directed to read from the local disks, but I do not know how
> I can differentiate between reads and writes in the IO rate
> on a per disk level.
> Any advice on how to size the correct intersite bandwidth
> required that will not degrade performance would be appreciated ?
Re: multi-site info..
Wrt to bandwidth, you are correct that with an OpenVMS cluster, one
typically configures shadow sets to read from the local members of the
shadow set. Only writes (updates) are propagated to the remote site,
hence the read-write ratios are a factor to consider in the link speed
A few pointers for consideration:
http://www2.openvms.org/kparris/ (Keith Parris's presentations)
(V7.3-2 shadowing doc)
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