Thanks for your quick reply.. Joe
I forgot to mentioned that we are using PropertyFileEndPointSnitch to provide cassandra about our network topology and below is property file uses by that class

cat rack.properties
10.9.0.6=east:r1b
10.9.0.18=east:r1c
10.9.0.14=east:r1d
10.9.0.10=west:r1a
default=east:rdef

In my first glance, VPNCubed uses openVPN software as part of transport layer so I did not look into it much deeper. I will work on it to see if it helps in out set up

we are looking for something like Oracle Primary/Standby solution where write operations happens only on Primary set of nodes ( in our case nodes those are running in different AZ in East region) and one copy of each data block should replicate to the node running in the West region so that read operation can be available local to any region because we have applications that consume cassandra data,  are running from both East and West regions. we are inclined to accept write latency between regions because readers won't look for data immediately and there will be around 5 -10 mins gap between write and read operations.

Is there any way to mark cassandra node to keep it as just for replication purpose and not to be as Primary for any data range in the ring? 

Niru

--- On Fri, 7/9/10, Joe Stump <joe@joestump.net> wrote:

From: Joe Stump <joe@joestump.net>
Subject: Re: RackAwareStrategy vs RackUnAwareStrategy on AWS EC2 cloud
To: user@cassandra.apache.org
Date: Friday, July 9, 2010, 1:41 PM

We had similar issues when we started running Cassandra on EC2 between multiple AZ's (not regions; we're working up to that shortly). We ended up building a rack aware strategy specific to AWS, which is posted somewhere in JIRA. Basically it uses the AWS API to ensure that replicants are stored in each AZ. We then ensure that our clients are only reading from nodes in a given AZ. What I'm guessing is that you're seeing latency issues between regions combined with a higher consistency level than what we use.

Also, SSL tunnels are hard to scale from the management side. The Amazon folks have told us that VPNCubed is a better solution for such things.

--Joe


On Jul 9, 2010, at 11:36 AM, maneela a wrote:

Are there any known performance issues if cassandra cluster launched with RackAwareStrategy because I see huge performance difference between RackAwareStrategy vs RackUnAwareStrategy.  Here are details:


we have a cluster setup with 4 EC2 X large nodes, 3 of them are running in East region and 4th one is running in West region and they all communicate with each other through VPN tunnel interface which is only way we found to achieve ring architecture across Amazon cloud regions:


we are able to process 3.5K write operations per second when we used RackUnAwareStrategy whereas 

:/home/ubuntu/cassandra/contrib/py_stress# ./stress.py -o insert -n 80000 -y regular -d ec2-xxx-xxx-xxx-xx.compute-1.amazonaws.com --threads 100 --keep-going
total,interval_op_rate,avg_latency,elapsed_time
35935,3593,0.0289930914479,10
70531,3459,0.0289145907593,20
80000,946,0.0267288666213,30

whereas we are able to process only 250 write operations per second when we used RackAwareStrategy

:/home/ubuntu/cassandra/contrib/py_stress# ./stress.py -o insert -n 80000 -y regular -d ec2-xxx-xxx-xxx-xx.compute-1.amazonaws.com --threads 100 --keep-going
total,interval_op_rate,avg_latency,elapsed_time
2327,232,0.434396038355,10
4772,244,0.40946514036,20
7383,261,0.384504625415,30
9924,254,0.392919449861,40
12525,260,0.383832110482,50
15158,263,0.378838069983,60
17784,262,0.383219807364,70
20416,263,0.381646275973,80
23030,261,0.382550528602,90
25644,261,0.384442176815,100
28268,262,0.380935921084,110
30910,264,0.377376309224,120
33541,263,0.385158945698,130
36119,257,0.387976026517,140
38735,261,0.382333525368,150
41342,260,0.38413751514,160
43925,258,0.387684800391,170
46642,271,0.36899637237,180
49291,264,0.378489510164,190
51931,264,0.3793784538,200
54573,264,0.378474057217,210
57253,268,0.374258003573,220
59884,263,0.380020038658,230
62484,260,0.387267011954,240
64728,224,0.439328571054,250
67340,261,0.389221810455,260
69920,258,0.386144905127,270
72531,261,0.384242234948,280
75202,267,0.372129596605,290
77843,264,0.354621512291,300
80000,215,0.183918378283,310

Thanks in advance

Niru