On 22 August 2010 23:22, Oleg Goldshmidt <p...@goldshmidt.org> wrote: > > On Sun, Aug 22, 2010 at 2:25 PM, Amos Shapira <amos.shap...@gmail.com> wrote: > > > We are a little concerned about the situation of two guests mounting > > the ext3 and starting to manipulate the sqlite files on it in > > parallel. > > I think you should be *very* concerned about the situation where 2 > guests mount an ext3 partition and start to manipulate files > *sequentially*. It looks like you *are* concerned (rightly), since you > wrote that only one client *mounts* the partition at a time.
Yes. But apart from hoping that RHCS does its job right, there is nothing preventing other guests from mounting the same partition in parallel. > > > Another option was to allow all guests to mount the file > > system read/write but carefully configure each guest to "own" > > different files or directories of sqlite files on the FS. > > What if one starts, e.g., creating files or appending content to > existing files (and allocating new blocks, etc., in the process)? The > other clients won't be aware of it. 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. > > I admit I have not thought long and hard about it, but it sounds > dangerous to me. 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. Cheers, --Amos _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
