Hi Mark, On Tue, May 21, 2013 at 6:46 PM, Mark Brown <ntdeveloper2...@yahoo.com>wrote:
> Hello, > I had a few more basic Swift questions.. > > 1. In Swift, when a rebalance is happening, does the client have write > access to the object? Does Swift have a mechanism to lock down one copy > which it is moving, and allow updates to the remaining two copies and do a > final sync somehow? What is the mechanism? > When the ring rebalances, it is allowed to only move one replica of a partition. This guarantees that you still have 2 available while replication is moving the partitions around. > 2. I did see that Swift has a configurable number of replicas. Can it be > set to 1? If it is set to 1, how does it work for the question above w.r.t > rebalance? I do understand a single replica does not make sense, I did want > to understand what it does in that case though. > It can be set to 1, and I think the default devstack install may do exactly that. Pretty much any guarantees of swift go out the window with 1 replica. I would expect that the partitions that are being moved would not be available until replication has moved them. > 3. If one of the nodes returns an error during a PUT(say, disk full), the > request is sent to the handoff node, but how is the handoff node configured > in the ring? Is it a special entry, or is it picked based on some algorithm > or something else? > There is an algorithm in the ring code that deterministically determines the handoff nodes. -- Chuck
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