[CentOS] Way OT ... originally "Good value for /proc/sys/vm/min_free_kbytes
MrKiwi
mrkiwi at gmail.com
Fri Dec 8 19:52:41 UTC 2006
Morten Torstensen wrote:
> John R Pierce wrote:
>> in our case, our production systems are a very large very complex
>> realtime oracle database running on large scale Sun enterprise
>> hardware on bigiron EMC storage, using dozens and dozens of raid10
>> logical volumes as you do NOT want to have a single 10TB volume,
>> sorry. by hand optimizing the tablespace layouts of the applications
>> tables and indicies, which have very specific access patterns, we can
>> get double the throughput of the blind 'just stripe the universe'
>> approach. Since
>
> Oh you would not have a single 10TB volume of course: and it is still a
> little quaint to hand optimize tablespaces. That is something we did in
> the 90s. Our own tests on multi-TB databases and modern SAN systems,
> the shotgun approach beat hand optimization every time. And we are
> talking about people with dozens of years with SQL optimization behind
> them. Intelligent I/O prefetch adaption, intelligent and dynamic access
> plans... the world of performance in the RDBM world is changing and old
> rules for performance are changing with it.
>
Im not sure im following the language correctly ...
Morten and John - you seem to be at opposite ends of the
opinion scale about hand optimising tablespaces?
Maybe you have different definitions of "hand optimising
tablespaces"?
Morten - Are your systems similar enough to Johns to make a
valid comparison about the merits of the shotgun approach vs
"hand optimising tablespaces"?
For the benefit of the rest-of-us DBAs, i understand "hand
optimising tablespaces" to mean ...
"choosing where a table (or a partition of a table) will
physically live, and where its indexes will live so that
roughly;
sum(reads/s + writes/s on spindle [1..n])^2 ) is as low as
possible. (ie balanced across all spindles). I have never
had a db span anything bigger than a redundant fibre channel
array controller (yep - a bit outdated now), but if it did,
then balance across n controllers as well.
I imagine you also decide if/which tables or indexes are
pinned in memory?
Thanks to both of you for the info so far :)
Regards,
MrKiwi
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