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Re: I/O-Performance with HP EVA 4000
From: Henrik Hempelmann (henrik.hempelmannsap.com)
Date: Thu Feb 16 2006 - 07:16:26 CST
Robert Klemme wrote:
> 2006/2/16, Kittel, Martin <martin.kittelsap.com>:
>>>> isnt the engine supposed to know the size of tables?
>> with release 7.6 it does. For tables created in release 7.6 they are always available. However, if you have migrated from a lower release (e.g. 7.5) these counters have to be initialized first. With release 7.6.00.16 it's easiest to do this by doing 'Check Data With Update' in admin mode on your database. In a future release these counters will be initialized automatically while the database is idle.
>> You can check the current values for the sizes in the system table FILES. Files whose counters haven't been initialized yet will show NULL values for the sizes. To get the name of the tables you can join the column FILEID with TABLEID from TABLES (or FILEID from INDEXES for indexes).
> Just wanted to make sure I didn't miss anything: this refers only to
> the COUNT(*) issue, does it? Are there any other IO speed related
> optimizations that make performance behavior differ significantly
> between 7.5 and 7.6 (even if only for certain usage scenarios)? Thx!
we are currently working on speeding up the read i/o performance.
It will be possible to assign larger tables with few changing records
to a continous clustered storage area. This allows us to read larger
chunks of data in one i/o call, which actually improves read
... this will happen in a upcomming 7.6 release.
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