On May 22, 2008 17:52 +0800, Stu Midgley wrote: > Just wondering if the user-space port of lustre servers to Solaris/ZFS > will have normal fs caching, or will they do direct IO? That is, the > lustre servers will effectively get caching simply by being in user > space. We have an application that would significantly benefit from > caching on lustre server side. We are happy to forgo reliability in > the face of crashes to get it.
The implementation of ZFS is segmented into several major functional units. The data management unit (DMU) is the bulk of the on-disk structure and is what Lustre will actually interface with for the MDT/OST. The adaptive replacement cache (ARC) is the cache management code and is used to manage manage memory in both userspace and the Solaris kernel. As a result, the userspace servers do not benefit at all from having a duplicate kernel-side cache, like any large database implementation, so we will be avoiding that as best possible. Initially we were doing O_DIRECT IO, but using async IO (libaio) showed much better performance for the way the ARC submits IO to disk. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
