2008/10/18 Stas Oskin <stas.oskin at gmail.com>: > Hi. > > I'm evaluating GlusterFS for our DFS implementation, and wondered how it > compares to KFS/CloudStore? > > These features here look especially nice > (http://kosmosfs.sourceforge.net/features.html). Any idea what of them exist > in GlusterFS as well? Stas, Here's how GlusterFS compares to KFS, feature by feature: > Incremental scalability: Currently adding new storage nodes requires a change in the config file and restarting servers and clients. However, there is no need to move/copy data or perform any other maintenance steps. "Hot add" capability is planned for the 1.5 release. > Availability GlusterFS supports n-way data replication through the AFR translator. > Per file degree of replication GlusterFS used to have this feature, but it was dropped due to lack of interest. It would not be too hard to bring it back. > Re-balancing The DHT and unify translators have extensive support for distributing data across nodes. One can use unify schedulers to define file creation policies such as: * ALU - Adaptively (based on disk space utilization, disk speed, etc.) schedule file creation. * Round robin * Non uniform (NUFA) - prefer a local volume for file creation and use remote ones only when there is no space on the local volume. > Data integrity GlusterFS arguably provides better data integrity since it runs over an existing filesystem, and does not access disks at the block level. Thus in the worst case (which shouldn't happen), even if GlusterFS crashes, your data will still be readable with normal tools. > Rack-aware data placement None of our users have mentioned this need until now, thus GlusterFS has no rack awareness. One could incorporate this intelligence into our cluster translators (unify, afr, stripe) quite easily. > File writes and caching GlusterFS provides a POSIX-compliant filesystem interface. GlusterFS has fine-tunable caching translators, such as read-ahead (to read ahead), write-behind (to reduce write latency), and io-cache (caching file data). > Language support This is irrelevant to GlusterFS since it is mounted and accessed as a normal filesystem, through FUSE. This means all your applications can run on GlusterFS without any modifications. > Deploy scripts Users have found GlusterFS to be so simple to setup compared to other cluster filesystems that there isn't really a need for deploy scripts. ;) > Local read optimization As mentioned earlier, if your data access patterns justify it (that is, if users generally access local data and only occassionly want remote data), you can configure 'unify' with the NUFA scheduler to achieve this. In addition, I'd like to mention two particular strengths of GlusterFS. 1) GlusterFS has no notion of a 'meta-server'. I have not looked through KFS' design in detail, but the mention of a 'meta-server' leads me to believe that failure of the meta-server will take the entire cluster offline. Please correct me if the impression is wrong. GlusterFS on the other hand has no single point of failure such as central meta server. 2) GlusterFS 1.4 will have a web-based interface which will allow you to start/stop GlusterFS, monitor logs and performance, and do other admin activities. Please contact us if you need further clarifications or details. Vikas Gorur Engineer - Z Research
