From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Date: Fri, 18 Apr 2008 18:22:17 -0600 Subject: [Lustre-devel] New Pools DLD In-Reply-To: <18373.20125.724151.421930@gargle.gargle.HOWL> References: <20080225100425.GC3108@webber.adilger.int> <18373.20125.724151.421930@gargle.gargle.HOWL> Message-ID: <20080419002217.GC2775@webber.adilger.int> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org On Feb 27, 2008 14:50 +0300, Nikita Danilov wrote: > Andreas Dilger writes: > > are you aware of any desirable LOV EA changes that would be good to > > include with the changes for the v3 "pool" EA (attached)? Are there > > any changes that are desirable for e.g. FIDs or similar? > > I think that if we are introducing incompatible LOV EA format, we can as > well go forward with changes hinted to at > > http://arch.lustre.org/index.php?title=MDS_striping_format#Future_developments Nikita, sorry to take a long time to get back to this issue, but I think it is quite valuable to pursue if we are already going to change the on-disk format. Since we are already need to change the LOV_MAGIC value, we may as well do as you suggest and have 0x0BD3ssss instead of 0x0BD30BD0, where ssss = size of EA in bytes. That would limit us to a 65536-byte striping EA, but it still larger than what is supported today, and the plans for wide striping also do not call for larger EAs. Even supporting 64kB EAs would be an issue with the current nifrastructure because the client always has to preallocate a receive buffer large enough for the largest EA because it does not know the EA size in advance. The question is whether you think we should also add a magic + size to the lov_ost_data_v1 structure, which is currently the same for all EA types. Adding a per-stripe magic + size would reduce the number of stripes we can allocate per file, and the 160-stripe limit is already a problem for some systems with more than 160 OSTs. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.