This changed recently. The CFS folks can say between which versions. Zero used mean ALL, it now means ONE. - Tom --- Tomas Hancock, Hewlett Packard, Galway. Ireland +353-91-754765 -----Original Message----- From: lustre-discuss-admin@lists.clusterfs.com [mailto:lustre-discuss-admin@lists.clusterfs.com] On Behalf Of David Vasil Sent: 13 January 2006 17:56 To: lustre-discuss@lists.clusterfs.com Subject: [Lustre-discuss] stripe_count = 0 vagueness Reading the man page for lmc, it says stripe_count = 0 will use the "currently optimal number of stripes". What does this mean? I was under the impression that using 0 as the stripe_count will make it stripe across all OSTs. However, when using 0 with lmc, the following INFO is given by lmc: INFO: default stripe count (0) - will use 1 stripe(s) per file Could someone please elaborate on what the effects are of setting the stripe_count to 0? Thanks! -- | David Vasil <dmvasil@ornl.gov> | Oak Ridge National Laboratory NCCS Division High Performance Computing | Systems Administrator | Bldg: 5600-A115 Phone: (865)241-5562 _______________________________________________ Lustre-discuss mailing list Lustre-discuss@lists.clusterfs.com https://lists.clusterfs.com/mailman/listinfo/lustre-discuss
On Jan 13, 2006 12:55 -0500, David Vasil wrote:> Reading the man page for lmc, it says stripe_count = 0 will use the > "currently optimal number of stripes". What does this mean?Lustre currently performs best when having fewer stripes per file, except in some specific cases. In the vast majority of cases it doesn''t make sense to stripe files over a large number of OSTs, and with the growth of Lustre filesystems to sometimes have hundreds of OSTs this would be a bad "optimal" striping to pick.> I was under the impression that using 0 as the stripe_count will make > it stripe across all OSTs. However, when using 0 with lmc, the following > INFO is given by lmc: > > INFO: default stripe count (0) - will use 1 stripe(s) per file > > Could someone please elaborate on what the effects are of setting the > stripe_count to 0? Thanks!Currently, setting a stripe count "0" is identical to specifying "1". In the future this may be changed to be 2 or some other number that gives better general-purpose performance. If your environment does better with some larger number of stripes you should specify that striping explicitly in the config. We may also add the ability to use "-1" to mean "stripe over all OSTs", but that isn''t done yet. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.
David Vasil wrote:> Reading the man page for lmc, it says stripe_count = 0 will use the > "currently optimal number of stripes". What does this mean? I was > under the impression that using 0 as the stripe_count will make it > stripe across all OSTs. However, when using 0 with lmc, the following > INFO is given by lmc: > > INFO: default stripe count (0) - will use 1 stripe(s) per file > > Could someone please elaborate on what the effects are of setting the > stripe_count to 0? Thanks!As of 1.4.5, stripe count 0 will use 1 stripe for file. You are correct, in previous versions this would default to striping across all OSTs. Based on experience we decided that was not the optimal default, so we''re currently using ''1''. ''currently optimal number of stripes'' == ''whatever we think works best for a default'' :) cliffw>
Reading the man page for lmc, it says stripe_count = 0 will use the "currently optimal number of stripes". What does this mean? I was under the impression that using 0 as the stripe_count will make it stripe across all OSTs. However, when using 0 with lmc, the following INFO is given by lmc: INFO: default stripe count (0) - will use 1 stripe(s) per file Could someone please elaborate on what the effects are of setting the stripe_count to 0? Thanks! -- | David Vasil <dmvasil@ornl.gov> | Oak Ridge National Laboratory NCCS Division | High Performance Computing Systems Administrator | Bldg: 5600-A115 Phone: (865)241-5562