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Post: Experiment on Elastic Scale-out with VoltDB Community Edition

Experiment on Elastic Scale-out with VoltDB Community Edition
nkatsip
Nov 19, 2013
Hello,

I am a PhD student and I currently work on some scaling-out problems of Parallel DBMSs. I chose to work with VoltDB and I plan to follow the following scheme in order to simulate elastic scale-out in my cluster:


  1. Have a 2-node cluster.
  2. Provision a node in my cluster to be a scale-out node.
  3. After the DB Initialization, I turn off the scale-out node (just stop the process and make it in-operational).
  4. I start a client application that increasingly needs more throughput.
  5. By the time my cluster cannot respond quickly enough (response-time has increased), I start my scale-out node
  6. After the scale-out node recovers from its failure (data have been sent over), it can respond to the client requests.
  7. The client's requests are served by both machines.


    The way I thought the afore-mentioned can be done, is by enabling the k-safety in my 2-node cluster. I start my 2-nodes and after the DB is initialized, I stop the scale-out node. When I need more throughput, I just start the scale-out node and by the time it is ready, requests are served by both machines.

    However, the Community Edition of VoltDB does not support k-safety, so If I turn off my scale-out node after the DB Initialization, my server goes down. Is there any other way around in order to simulate the afore-mentioned scheme? Is there any way I can have access to a VoltDB edition with k-safety so I can conduct my experiments?

    Thank you for your time.
jpiekos
Nov 19, 2013
K-safety is essentially "high availability" rather than scale-out. While k-safety can help read throughput (replicas can service read requests), write requests must happen on all replicas synchronously - adding more k-safety doesn't increase scale-out for writes.

Since v3.5 our Enterprise version supports adding nodes to an existing k=0 cluster. Adding nodes will increase both throughput capability, as well as database size capacity. You can download our Enterprise kit from our website, it includes at 30 day trial license within the installation package.

John
nkatsip
Nov 19, 2013
John, first of all thank you for your immediate response.

I am aware of k-safety's initial purpose, I just wanted to simulate scaling-out by following the approach of some people from University of Waterloo. These
guys did what I described in the first post in order to simulate elastic scaling-out.

That is actually really nice. I will use the Trial Version of the Enterprise edition then.

Thank you again.
nkatsip
Nov 19, 2013
John, I just realized that in order to download the Enterprise kit I from your website, I need to fill out a form. I have filled out this form numerous, but I never received a reply email with a download link for the 30 day trial. Why is this happening? I also have been checking my Spam folder and there is nothing there also.
jpiekos
Nov 19, 2013
You may have opted out at some point, and our system won't send you emails if you requested to opt-out. Email me your email address at jpiekos/voltdb.com and I can get you opted back in.

John