Hello Folks,
So I'm trying to get a theoretical understanding of stripe offsets in
lustre. As I understand it, the default offset set to 0 results in all writes
beginning at OSS0-OST0. With a default stripe of 4, doesn't this lead to
massive hotspots on OSS0-OST[0-3] (unless *all* writes are consistently large)?
With our setup, we have 4 OSTs per OSS (well, the last OSS has 3, but
that's not important right now). This would appear, in theory, to put OSS0 in
a very hot situation.
That said, I wonder how efficient a solution setting the stripe offset
of the root of the file system to -1 ("random") is to solving this theoretical
situation (given my understanding of striping under lustre).
In reality, we have a quite varied workload on our file systems with
codes ranging from bio to astrophys and, as such, writes ranging from very
small to very large. Any real-world experience with these situations? Are
there strange inefficiencies or administrative difficulties that should be
known previous to enabling "random" offsets? Any info would be greatly
appreciated.
----------------
John White
High Performance Computing Services (HPCS)
(510) 486-7307
One Cyclotron Rd, MS: 50B-3209C
Lawrence Berkeley National Lab
Berkeley, CA 94720
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