Open Stack

Thanks Chuck.

Just one more question about rebalancing. Have there been measurements on how much it affects performance when a rebalance is in progress? I would assume its an operation that puts some load on the system, while also keeping track of  whether the original object changed while moving, among other things. Its probably not that frequent, but it would be great to understand how it works in the real world with large workloads.

I did have a general question about container sync. Is it something that is used a lot, and works well?

-- Mark


________________________________
 From: Chuck Thier <cthier at gmail.com>
To: Mark Brown <ntdeveloper2002 at yahoo.com> 
Cc: Openstack <openstack at lists.launchpad.net> 
Sent: Wednesday, May 22, 2013 7:26 AM
Subject: Re: [Openstack] Swift questions
 


Hey Mark,
On Wed, May 22, 2013 at 8:59 AM, Mark Brown <ntdeveloper2002 at yahoo.com> wrote:

Thank you for the responses Chuck.
>
>
>As part of a rebalance, the replicator, I would assume, copies the object from the old partition to the new partition, and then deletes it from the old partition. Is that a fair assumption?

That is correct, the replicators will replicate the data in the partition at the new location.  The server that has the old data will delete it once it is certain that data is available in all replicas.
 
Also, is there anything that explains in more detail how the handoff node is picked? What if the ring changes and the data still lives on the handoff node? 

I don't think there is currently any documentation that describes how handoff nodes are picked.  Handoff nodes can be used for a variety of reasons, including when servers are down, or not responding.  The server that has handoff partitions is always responsible for getting the data to the correct location.

There is some more detailed information on replication at: 

http://docs.openstack.org/developer/swift/overview_replication.html

(if you haven't read it yet)

--
Chuck
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