| Arne Joris 2004-10-21, 5:45 pm |
| Bill Todd <billtodd@metrocast.net> wrote:
> it sounds like the distributed meta data service would create a
>
> Not really: where the metadata is processed has relatively little to do
> with what disk it's obtained from, unless the system goes to some
> essentially orthogonal effort to access the most local copy available.
But my metadata would also be replicated to both sites, so disk access
is *always* local (but writes are being replicated synchronously so
would be a bit slow). In that case, having meta data operations handled at
the site that is about to do I/O would not introduce *any* cross-WAN
operations at all.
>
> It doesn't sound as if you really care much about remote metadata access, at
> least as long as the amount of metadata processed is negligible compared
> with the amount of data fetched. Inter-site latencies tend not to become
> *really* noticeable until distances in the hundreds of miles are involved
> (100 miles being on the order of a millisecond, one-way).
I have latencies of 100ms round trip (thousands of miles plus the WAN is
routed which introduces switching latencies).
> And if you're mostly reading large files sequentially, it doesn't sound as
> if latency should be any real concern there, either. But unless you've got
> unlimited bandwidth between the two sites, your desire to do reads locally
> is understandable.
Yeah my main concern is not meta data access, I care mostly about data
being accessed locally.
Arne Joris
|