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DD command using block device as input
Post 302666061 by Corona688 on Tuesday 3rd of July 2012 03:43:10 PM
07-03-2012
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So far with my tests I find that reading 16kb takes about the same time as reading 512b.
Too bad there isn't a tool which can tell you more about what your disk's doing, test uncached reads, or even configure hardware read-ahead to your preference... something like hdparm...
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I need this information to set the optimal page size of my system (oracle and mysql suggest these sizes)
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Can you elaborate on why dropping the caches is a bad idea?
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How about this sudo procedure:
- drop_caches
- flush disk-cache with hdparm
- make sure dd is in memory
- position the read head randomly on disk
- with DD: read X amount of bytes from the beginning of my file (this is timed)
- drop_caches
- flush disk-cache with hdparm
- make sure dd is in memory
- position the read head randomly on disk
- with DD: read X amount of bytes from the beginning of my file (this is timed)
Last edited by Corona688; 07-03-2012 at 04:51 PM..
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ppi::token::quotelike
PPI::Token::QuoteLike(3) User Contributed Perl Documentation PPI::Token::QuoteLike(3) NAME
PPI::Token::QuoteLike - Quote-like operator abstract base class INHERITANCE
PPI::Token::QuoteLike isa PPI::Token isa PPI::Element DESCRIPTION
The "PPI::Token::QuoteLike" class is never instantiated, and simply provides a common abstract base class for the five quote-like operator classes. In PPI, a "quote-like" is the set of quote-like things that exclude the string quotes and regular expressions. The subclasses of "PPI::Token::QuoteLike" are: qw{} - PPI::Token::QuoteLike::Words `` - PPI::Token::QuoteLike::Backtick qx{} - PPI::Token::QuoteLike::Command qr// - PPI::Token::QuoteLike::Regexp <FOO> - PPI::Token::QuoteLike::Readline The names are hopefully obvious enough not to have to explain what each class is. See their pages for more details. You may note that the backtick and command quote-like are treated separately, even though they do the same thing. This is intentional, as the inherit from and are processed by two different parts of the PPI's quote engine. SUPPORT
See the support section in the main module. AUTHOR
Adam Kennedy <adamk@cpan.org> COPYRIGHT
Copyright 2001 - 2011 Adam Kennedy. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of the license can be found in the LICENSE file included with this module. perl v5.16.2 2011-02-25 PPI::Token::QuoteLike(3)