On Jul 31, 2011, at 12:08 PM, <jonathan.hw...@accenture.com>
<jonathan.hw...@accenture.com> wrote:
> I was asked by our IT folks if we can put hadoop name nodes storage using a
> shared disk storage unit.
What do you mean by "shared disk storage unit"? There are lots of
products out there that would claim this, so actual deployment semantics are
important.
> Does anyone have experience of how much IO throughput is required on the name
> nodes?
IO throughput is completely dependent dependent upon how many changes
are being applied to the file system and frequency of edits log merging. In
the majority of cases it is "not much". What tends to happen where the storage
is shared (such as a NAS) is that the *other* traffic blocks the writes for too
long because it is overloaded and the NN declares it dead.
> What are the latency/data throughput requirements between the master and
> data nodes - can this tolerate network routing?
If you mean "different data centers", then no. If you mean "same data
center, but with routers in between", then probably yes, but you add several
more failure points, so this isn't recommended.
> Did anyone published any throughput requirement for the best network setup
> recommendation?
Not that I know of. It is very much dependent upon the actual workload
being performed. But I wouldn't deploy anything slower than a 1:4 overcommit
(uplink-to-host) on the DN side for anything real/significant.
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Lawyers are funny people. I wonder how much they got paid for this one.
