IDS Forum

RE: Cooked files vs Raw disc

Posted By: Michaelis, Daniel
Date: Thursday, 9 December 2004, at 3:47 p.m.

In Response To: Cooked files vs Raw disc (Peter J Diaz de Leon )

O.K... I just can't stand it...

First, you can NEVER "make up" the 10 to 15% difference; think about it.
Yes, you can make things faster with a caching controller with lots of
memory, but they'll always be 10 to 15% faster on the same hardware if you
use raw space than if you use cooked space. To say that it is "time
consuming" to set up raw partitions (unless you're on a Windows platform,
and then I can't speak to raw space) demonstrates a lack of understanding in
what is involved in setting up file systems. On any of the Unix platforms
I've ever worked on, the work to set up a file system is slightly greater
than setting up the raw logical volume (since file systems typically sit on
top of raw volumes, this makes sense). So unless you're willing to be
COMPLETELY ignorant about where your data resides, letting your system
administrator just drop your database on whatever disk he/she happens to
have handily lying about, you're not really saving yourself any effort. And
then, you will have reduced the price/performance ratio of your hardware by
the 10 to 15%.

Second... I can't say that I've ever tried moving an instance using the
method specified. I can't say that I think it's a good idea either. There
are just too many ways that I think that could get hosed up. That said,
there's no reason that you couldn't do this with raw space if you wanted to;
the command is just a little different. With the cooked files, you'll have
to do an FTP of the files from one system to the other; with raw space,
you'd first do a
dd if=<your_raw_device> of=<some_file_name>
Then FTP the <some_file_name> file to the remote system, finally doing a
dd if=<some_file_name> of=<remote_raw_device>
and you've accomplished the same thing. I'll admit, it's a little more
complex, but not all that much more complex.

Further, by keeping your data in raw files, you are less likely to run into
folks who think that you don't need to do database backups because, "We do
an O/S backup every night, and those files are included in the backup"... or
the system administrator who calls you saying, "Well, the
/var/<your_database> file system was filling up, so I gzip'ed all those
files there... I've gotten a few calls, and I was wondering if you could
help me... " In short, raw files provide you with a "reminder" that you're
dealing with things that should NOT be managed by the operating system in
the first place.

My experience has been that people are resistant to raw devices at first,
because they are not accustomed to them, but once you've implemented them,
folks begin to realize that there's very little difference in the
administration of the database with raw vs cooked files, and you get that
bonus 10 to 15% performance boost. Hard to argue against it...

Dan Michaelis

Database Administrator/Developer
eOriginal
351 West Camden Street
Suite 800
Baltimore, MD 21201

410.625.5187 (phone)
410.659.9799 (fax)


-----Original Message-----
From: Peter J Dia.... [mailto:pdiazdeleon@infinityhealthcare.com]
Sent: Thursday, December 09, 2004 2:28 PM
To: ids@iiug.org
Subject: Cooked files vs Raw disc [3863]


I has a bit of a discussion with one of our developers today and the
topic of cooked vs raw file systems came up, and I am looking
for opinions.

Reason 1 for not using raw disc was that a 10% to 15% reduction in
performance can be made up in hardware
using a caching controller with lots of memory. Also the time involved
in setting up and maintaining raw partitions is to time
consuming.

Reason 2 for not using raw disc was that if you use cooked files when
its time to move from the test environment to production
you can just TAR or ZIP up the cooked files and transfer them to
production and you are guaranteed that the tested TEST environment get
to production.


Thoughts?

Thanks




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Messages In This Thread

• Cooked files vs Raw disc
  Peter J Diaz de Leon -- Thursday, 9 December 2004, at 2:28 p.m.
  • RE: Cooked files vs Raw disc
    Gregory S. Williamson -- Thursday, 9 December 2004, at 3:10 p.m.
    • RE: Cooked files vs Raw disc
      Juan Manuel Naranjo -- Thursday, 9 December 2004, at 3:28 p.m.
  • RE: Cooked files vs Raw disc
    Michaelis, Daniel -- Thursday, 9 December 2004, at 3:47 p.m.
  • RE: Cooked files vs Raw disc
    malcolm weallans -- Thursday, 9 December 2004, at 6:10 p.m.
    • RE: Cooked files vs Raw disc
      Obnoxio The Chav -- Friday, 10 December 2004, at 3:17 a.m.

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