On Wed, May 23, 2012 at 8:11 PM, NNever <nnever...@gmail.com> wrote: > Thanks J-D. > > so it means 'Append' keeps write-lock only and 'Put' keeps > write-lock/read-lock both?
Yeah... not at all. First, there's no read lock. Then Put is just a Put, it takes a write lock. Append is a read+write operation, still just uses a write lock. > and if we use 'Append' instead of 'Put', then the chance Clients to wait > will reduce, right? You would use Append instead of Put only if you also need a Get. A typical example is a list, let's say you have a cell that's like: a,b,c Now you want to add ",d". Before Append you'd have to do a Get, manipulate the value (basically add the new data at the end) and then do a Put. That's 2 round trips. Append is just those operations put together and it runs all in the region server, saving you 1 round trip plus you don't have a race condition when you have multiple appenders on the same cell. Hope this helps, J-D
