On 23 August 2010 04:42, Etzion Bar-Noy <eza...@tournament.org.il> wrote: > > Inline > > On Sun, Aug 22, 2010 at 4:41 PM, Amos Shapira <amos.shap...@gmail.com> wrote: >> >> Yes. But apart from hoping that RHCS does its job right, there is >> nothing preventing other guests from mounting the same partition in >> parallel. >> > Of course there is - LUN masking. Its purpose is exactly this. You expose the > LUN *only* to the nodes which require direct access to it.
The issue is that we want all our internal servers to be able to mount any of LUN's, as the "shards" of the multi-FS-multi-sqlite migrate among them. There is no way to dynamically mask and unmask LUN's, as it is now adding a new LUN requires a server reboot. >> That's why we looked at cluster-aware file systems in form of GFS but >> decided the performance hit is too great to go with it. A brief look >> at OCFS installation steps gave an impression that it isn't trivial or >> well supported on CentOS 5. > > Incorrect impression. Less than 5 minutes work, being extra slow, with coffee > included. Simple enough? Thanks for the info. Do you have a good pointer to follow? Have you compared OCFS performance to GFS and ext3? >> It is. As was pointed out earlier in this thread - a large part of the >> "file system" is about how the file system module "caches" information >> in memory and synchronises it on the disk. If it's not a cluster-aware >> file system then parallel mounting is equivalent to opening the LV or >> device by an application and randomly starting to write data on it. > > True. But cluster-aware FS should be considered carefully. For some purposes, > they ease management. For some others, they complicate it. > GFS has always been misunderstood by me. It has little benefits, and major > drawbacks. Can't see any reason to use it, from the existing variety of > clustered FS around. What drawbacks and compared to what? We've noticed the performance problem when we tried it. What are other *practical* alternatives? GFS comes built-in and supported in RHEL/CentOS and the RHCS, that's why it was the almost "natural choice" in our mind. Thanks, --Amos _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
