Re: B*-trees

From: <cbbrowne_at_hex.net>
Date: Fri, 12 Jan 2001 04:17:45 GMT
Message-ID: <wklmsh3cwv.fsf_at_mail.hex.net>

>>>>> "Christoph" == Christoph Rupp <chrrupp_at_rz.fh-augsburg.de> writes:

>>> Depending on the structure of your data, reading from one file
>>> could also be faster, if one read operation gets more than one
>>> index table. Sure, the head of the harddrive doesn't have to move
>>> that far... now it's clear to me.
 

>> You can never be sure, what the head does.  Typically repositioning
>> the file cursor takes more time than reading a multiple amount of
>> data.

Christoph> Yesyes, that's what i meant. Therefore one file should be

Christoph> faster then several files. Thinking about many fragmented Christoph> files on my hard drive :)

Further complications are available...

-> If the data is cached in memory [competently designed OSes have

   commonly, since the 1970s, offered this feature], the disk may not    get hit for a read operation if the data is already in RAM.

-> Disk drives sometimes lie about what they're doing internally.

   They may claim to have some number of heads/sectors/clusters, but    underneath have other "geometry" so that you don't really know    what's going on.

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?OM ERROR

Received on Fri Jan 12 2001 - 05:17:45 CET