9eb797b099
Long explanation, but hopefully answers any questions. We don't like changing the default behavior of Swift unless there's a really good reason and, up until now, I've tried doing this with this new db_preallocation setting. For clusters with dedicated account/container servers that usually have fewer disks overall but SSD for speed, having db_preallocation on will gobble up disk space quite quickly and the fragmentation it's designed to fight isn't that big a speed impact to SSDs anyway. For clusters with account/container servers spread across all servers along with object servers usually having standard disks for cost, having db_preallocation off will cause very fragmented database files impacting speed, sometimes dramatically. Weighing these two negatives, it seems the second is the lesser evil. The first can cause disks to fill up and disable the cluster. The second will cause performance degradation, but the cluster will still function. Furthermore, if just one piece of code that touches all databases runs with db_preallocation on, it's effectively on for the whole cluster. We discovered this most recently when we finally configured everything within the Swift codebase to have db_preallocation off, only to find out Slogging didn't know about the new setting and so ran with it on and starting filling up SSDs. So that's why I'm proposing this change to the default behavior. We will definitely need to post a prominent notice of this change with the next release. Change-Id: I48a43439264cff5d03c14ec8787f718ee44e78ea
Swift ----- A distributed object store that was originally developed as the basis for Rackspace's Cloud Files. To build documentation run `python setup.py build_sphinx`, and then browse to /doc/build/html/index.html. The best place to get started is the "SAIO - Swift All In One", which will walk you through setting up a development cluster of Swift in a VM. For more information, visit us at http://launchpad.net/swift, or come hang out on our IRC channel, #openstack on freenode. -- Swift Development Team