Mornign Kishor,
--- kishor bhagwat aaaaarrrgghhh@yahoo.com wrote:
--- Nilesh Chaudhari listbox@nilesh.net wrote:
Animesh Singh wrote:
There should be little to no data loss in
soultion. zero data loss = 'synchronous' solution. anything other than this is async - where ur data loss is unpredictable - can be zero to any number of I/Os.
...
What will be the best way to have Disaster Recovery of site ( File & Print and Messaging
Soluton.
). at
remote location with approx. 300 km. distance. & with 2Mbps link.
one 2 Mbps IP link can transfer 2 x 0.8 x 1000 / 8 = 200 Kilobytes of data per second.(0.8 becoz 20% of IP overheads). That means your data at primary should have a change rate much less than this if you want synchronous replication.
<snip> But is it fesible to have Site1 synchronous replication with Site2, Site2 synchronous replication with Site3 and Site3 ynchronous replication with Site1 ?
There can never be `no data loss'. Some data is
always
lost in such incidents where a whole site goes down.
Not true. You can have zero data loss solutions - problem is...they need humungous bandwidth and/or they screw up your application response times.
<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.
You have these options for Linux/*nix -
- journalling file system
- tar, gunzip
- dd, cp
- fsck
- taper, cdrw-taper
- linux single
- http://linux-ha.org/
- http://www.linuxvirtualserver.org/
- and so on...
none of these will work. you need to use proprietary solutions that will intercept Write calls to the OS, transfer them to DR site, actually write to remote disk, get an acknowledge from there, write to local disk, and *only then* acknowledge a successful write to applcation.(now u know why zero data loss solutions cost a bomb and screw up app 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."
kishor
Regards, Aniemsh.
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