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From Paul Snively <psniv...@IFILM.com>
Subject Hibernate and JCS Questions
Date Thu, 05 Dec 2002 02:19:50 GMT
Gentlemen,

My name is Paul Snively. I'm the senior Java architect for
http://www.ifilm.com, the seventh-largest video-streaming service in the
world. We are in the process of redeploying our portal using Java
technology. To that end, we have been investigating Hibernate extensively,
and are now dealing with questions surrounding data caching. Our expected
infrastructure for this redeployment involves ~10 application servers,
possibly with another layer of a hopefully smaller number of machines, but
still >1, acting as data servers.

The Hibernate documentation goes into some detail regarding caching options,
and Gavin King has been kind enough to expand on that information still
further. In particular, our current understanding is that the use of JCS in
Hibernate is recommended for clustered read-only environments, but cannot be
used in clustered read-write environments. On the other hand, the JCS
documents make quite clear that clustered "put" operations are supported and
expected to work. Following Gavin's lead, one alternative that suggested
itself to us was simply to rely on Hibernate's session-level cache
exclusively and not use JCS at all, but feedback from Gavin suggests in no
uncertain terms that such an approach is counterindicated.

So our questions basically boil down to the following:

1) How mature is JCS? Who is using it? On how many machines? With which of
the three major configurations (fully distributed, client/server,
client/cluster)?

2) What was the process by which Gavin gained sufficient confidence in JCS
to include it in Hibernate?

3) Why does Gavin indicate that JCS can't be used in a clustered read-write
environment, in contradiction to the JCS documentation?

4) If we were able to commit to using Hibernate in a read-only fashion and
doing our data writing some other way, changing the data out from under
Hibernate, which various legacy admin tools will do anyway, does this change
the preference profile between Hibernate's session-level cache vs. JCS? If
so, how?

The bottom line, quite frankly, is that we're nervous about relying on JCS
in the absence of some reassurances about its maturity and use in the real
world, as JCS is clearly attempting to solve difficult engineering issues,
and this component will prove critical to our success should we choose to
use it. The clearest alternative to us is to rely on Hibernate's own
session-level caching and to do whatever we need to do in order to make that
as efficient as humanly possible. Any feedback about our options would be
most greatly appreciated.

Many thanks,
Paul Snively

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