On Dec 20, 2007 13:52 -0700, Peter Braam wrote: > I was hoping for 1. to keep things simple.
Presumably, an SNS layer would replace (or just extend?) the existing LOV functionality on the clients. We would definitely want to allow existing RAID 0 striped files to be usable by having the SNS-aware client understand the old LOV EA format, even if all new files are created with an enhanced SNS EA format. One feature that is quite desirable with SNS is to be able to add and remove full mirrors of the file (as opposed to restriping to change the layout in more complex ways) in an efficient manner. Since this functionality is already required to be able to reconstruct a missing mirror copy of a file it seems relatively straightforward to create a "ghost" mirror copy and then have the normal resync mechanism copy it. More complex layout changes (e.g. RAID0 striping to RAID5/6) can be done via the planned normal file migration/restripe mechanisms, and it should be up to the administrator to do this, as for some cases (e.g. scratch filesystem) it might not be worth the extra IO to restripe all the files and instead leave it up to normal file aging/purge to catch most of the files, and then have a later pass later to handle files that have a longer lifetimes. > Alexander Zarochentsev wrote: > > Coming SNS feature somehow duplicates and extents existing Lustre > > striping functionality. How will they (SNS and striping) coexist > > in the future versions of Lustre? > > > > I see 3 possible variants: > > > > 1. SNS replaces striping everywhere. > > 2. one file can be SNS striped object or lustre striping object. > > 3. one file can be SNS on top of Lustre-striping or Lustre-striping on > > SNS and, probably, one part of file can be SNS and another part is > > Lustre-striped. > > > > Does #3 makes any sense? > > > > I would prefer to assume that correct answer is (2) -- there are SNS > > files and Lustre-striped files, because Lustre-striped files probably > > have less overhead. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. _______________________________________________ Lustre-devel mailing list [email protected] https://mail.clusterfs.com/mailman/listinfo/lustre-devel
