[Info-vax] Wide area cluster, metro area network, seeking info

[Rich Jordan]

On Tuesday, June 15, 2021 at 12:55:10 PM UTC-5, Michael Moroney wrote:
> On 6/15/2021 9:24 AM, Arne Vajhøj wrote: 
> > On 6/11/2021 2:20 PM, Rich Jordan wrote: 
> >> On Thursday, June 10, 2021 at 10:22:58 AM UTC-5, Marc Van Dyck wrote: 
> >>> Rich Jordan was thinking very hard : 
> >>>> We are looking at the possibility of putting VMS boxes in two 
> >>>> locations, with 
> >>>> Integrity boxes running VSI VMS. This is the very beginning of the 
> >>>> research 
> >>>> on the possibility of clustering those two servers instead of just 
> >>>> having 
> >>>> them networked. Probably have to be master/slave since only two 
> >>>> nodes and no 
> >>>> shared storage. 
> >>>> 
> >>>> After reviewing the various cluster docs, they seem to be focused on 
> >>>> older 
> >>>> technologies like SoNET and DS3 using FDDI bridges (which would 
> >>>> allow shared 
> >>>> storage). The prospect has a metropolitan area network but I do not 
> >>>> have any 
> >>>> specs on that as yet. 
> >>>> 
> >>>> Are there available docs relevant to running a distributed VMS 
> >>>> cluster over a 
> >>>> metro area network or fast/big enough VPN tunnel? Or is that just the 
> >>>> straight cluster over IP configuration in the docs (which we've 
> >>>> never used) 
> >>>> that we need to concentrate on? 
> > 
> >>> Before going into the technical details, wouldn't it be interersting to 
> >>> know what you want to achieve, and discuss whether clustering is the 
> >>> best way to achieve it ? I, for one, would be interested to know why 
> >>> you 
> >>> believe that clustering without shared storage can be more beneficial 
> >>> than simple networking. 
> > 
> >> The point: the system at the second location will be a backup site 
> >> and/or disaster recovery box. There is no third location and I have 
> >> no info on the likelihood of getting one. 
> > If the business problem is to ensure that the second location always 
> > have a copy of all data, then a VMS cluster may not be the optimal 
> > solution. 
> > 
> > There are other VMS features/products than clustering that could 
> > be relevant.
> It appears to me one possibility is fiberchannel presenting RAID-1 
> units, with one member of each RAID-1 at the main site and one at the 
> backup site connected with dark fiber (FOIP?). VMS system (no cluster) 
> at main site and either no system or a cold backup at the backup site.

I love the discussions that questions like this bring up.

More info.  The base requirement is to have a backup system at an existing remote office; this backup system will be kept 'up to date' and available for use if the primary site or system fails.

One option is nightly backup/restore operations, so (up to) one day latency.  This is considered the low end of acceptable.  The customer asked about options for keeping the backup closer to current.

The system cannot be quiesced during production hours (about 11 hours per day weekdays) so we cannot run periodic backups during those hours.  Programs just were not written that way.

Since we can't do intraday backups, one option is shadowing, and so clustering.  I didn't mention HBVS (my bad) but its the reason for the cluster option.  I was mainly looking for info about running a cluster over a WAN connection/metro area network in case anyone had that experience, since much of the documentation available is pretty old and seems to concentrate on using FDDI bridges over what are currently modest speed links.  

VSI _is_ involved and we are working with them on this possibility.  At this point I think the additional license subscription costs are going to kill the HBVS/cluster option, especially if a third node was needed (and a third location and connection, and set of licenses).  That means going with the one-day latency backup option and generating and testing the procedures for failing back to the main system when it is available again.

We have not determined availability of dark fiber; the intention is to use the metro area network, and so cluster over IP.  We did some price checks on the equipment needed to bridge the sites and  I am told it is not within the budget.   

Thanks

Rich