--- Animesh Singh an2rhyme@yahoo.com wrote: <snip>
But is it fesible to have Site1 synchronous replication with Site2, Site2 synchronous replication with Site3 and Site3 ynchronous replication with Site1
you can definitely have any such configuration- but can u afford the b/w? Will you have people at 3 diff locations skilled enough to carry recovery processes? Its not practical. Typically you will have site 1 to 2 to 3, with 1 sync-replicating to site 2 which async-replicates to site 3.This is called a multi-hop config and is in use (even in India).
<snip> Very true, Veritas GCM, does same, with IP Bandwidth. This is no specific distance limitation that serves as the delimiter between synchronous & asynchronous modes of operation as it is really a dependency of network architecture ( i.e. SAN, switches, that can support the distance & subjective tolerance to the introduced latency.) A general rule of thumb that is sometimes deployed in enterprises is a latency time of less then 500 milliseconds, round trip.
GCM is a cluster solution(DNS-based). Its not a replication solution. I'm talking only abt data availability at DR site, not app availability (yet). There is no distance limitation for async, in the sense that it will work, but your risk of data loss increases as u go farther. Sync is a diff beast -I wouldnt go over 70 miles - beyond that you're going to hurt your response times.
<snip> What will be the impact of BIC TCP over 2Mbps link. They claim, "BIC can reportedly achieve speeds roughly 6,000 times that of DSL and 150,000 times that of current modems."
I dunno abt BIC. Once the SCSI data packets are in IP, your IP network takes over and you are free to do what u like.
regds, Kishor
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