[openib-general] SA cache design

[Brian Long]

On Thu, 2006-01-12 at 10:16 -0800, Sean Hefty wrote:
> Brian Long wrote:
> > How much overhead is going to be incurred by using a standard RDBMS
> > instead of not caching anything?  I'm not completely familiar with the
> > IB configurations that would benefit from the proposed SA cache, but it
> > seems to me, adding a RDBMS to anything as fast as IB would actually
> > slow things down considerably.  Can an RDBMS + SA cache actually be
> > faster than no cache at all?
> 
> I'm not sure what the speed-up of any cache will be.  The SA maintains a 
> database of various related records - node records, path records, service 
> records, etc. and responds to queries.  This need doesn't go away.  The SA 
> itself is perfect candidate to be implemented using a DBMS.  (And if one had 
> been implemented over a DBMS, I'm not even sure that we'd be talking about 
> scalability issues for only a few thousand nodes.  Is the perceived lack of 
> scalability of the SA a result of the architecture or the existing implementations?)
> 
> My belief is that a DBMS will outperform anything that I could write to store 
> and retrieve these records.  Consider that a 4000 node cluster will have about 
> 8,000,000 path records.  Local caches can reduce this considerably (to about 
> 4000), and if we greatly restrict the type of queries that are supported, then 
> we can manage the retrieval of those records ourselves.
> 
> I do not want end-users to have to administer a database.  However, if the user 
> only needs to install a library, then this approach seems worth pursuing.

What about SQLite (http://www.sqlite.org/)?  This is used by yum 2.4 in
Fedora Core and other distributions.

"SQLite is a small C library that implements a self-contained,
embeddable, zero-configuration SQL database engine."

/Brian/

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       Brian Long                      |         |           |
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