RE: Moving DR site from 30miles to 1600miles

You might need a more decent SSH client if your current one is
openSSH-based, which apparently does internally limit the send buffer sizes
even if your server defaults / maximum are set higher to math WAN latencies.
 
Check this link if you want a high-throughput version of SSH:
http://www.psc.edu/networking/projects/hpn-ssh/
 
64kB of send buffer for 1600 mile "wide" WAN is too low if you want to
achieve decent throughput. TCP as a reliable transport protocol needs to
have retransmit capability, thus needs to keep all packets in send buffer
until it's acknowledged by the other side, thus low buffer will start
throttling your throughput if the network roundtrip time is long.
 
You can actually calculate how large TCP buffers you need if you want to
fill x MB of your Oc3 link. Google for "bandwidth delay product" the formula
is very simple ( only three variables in the formula, link bandwidth, TCP
buffer size and packet transmit time which you can roughly measure with ping
or tnsping )
 
--
Regards,
Tanel Poder
http://blog.tanelpoder.com <http://blog.tanelpoder.com/> 

 



  _____  

From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Ravi Gaur
Sent: Wednesday, April 09, 2008 23:39
To: oracle-l@xxxxxxxxxxxxx
Subject: Moving DR site from 30miles to 1600miles


Hello all,

We are planning to move our DR site which is currently about 30 miles from
production site to ~1600 miles away. We currently have a 4-node RAC setup on
our production site that houses 3 production instances (all 10.2.0.3 on
Solaris 10). The SAN is Storagetek and we use ASM for volume management. 
In our testing, we are hitting issues in network transfer rates to the
1600-miles site -- a simple "scp" of 1GB file takes about 21 minutes.  We
generate archives at the rate of approx 1GB/8minutes. The network folks tell
me that the TCP setting is a constraint here (currently set to 64k
window-size which Sysadmins here say is the max setting). We have an Oc3
link that can transfer @ 150Mbps (that is what the networking team tells
me). 

I've an SR open w/ Oracle and have also gone thru few Metalink notes that
talk about optimizing the network from dataguard perspective. One of the
notes I came across also talks about cascaded standby dataguard setup (one
standby local pushes logs to the remote site).

I'm trying to collect ideas how others are doing it under similar scenarios
and if there is something we can do to utilize the entire network bandwidth
that we have available to us.

TIA,

- Ravi

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