Re: direct I/O with VxFS

From: Connor McDonald <hamcdc_at_yahoo.co.uk>
Date: Wed, 27 Jun 2001 08:07:40 -0700
Message-ID: <F001.0033A186.20010627081746@fatcity.com>

The argument for direct io is that if you already have a large cache (the oracle one), then its not much use having a second copy of that cache (the unix one) - that memory could possibly be better used elsewhere (supporting more users, large sort sizes etc etc etc)

So having direct io is giving more of the caching responsibility to the oracle buffer cache.

hth
connor

• KC <kchan_at_speednet.com.au> wrote: > Dear list,
  >
  > Our shop is running Solaris 2.6, Oracle database
  > 8.0.6 and Veritas VxFS file system. At present, all
  > database file access thru the file system buffer
  > cache, we decided to use the direct I/O mount option
  > with VxFS for performance reason. There is one issue
  > I am not sure about and hope someone on the list can
  > give me a pointer, access database file thu the file
  > system buffer cache gives us "read ahead" advantage,
  > with direct I/O I think what you read is what you
  > get (no read ahead functionality), is this an
  > issue?? If it is an issue, how do you deal with it??
  > WIth file system buffer cache, I think the database
  > block size should be the same as file system buffer
  > size and file system block size is irrelevant to how
  > much system read or write, is this still true under
  > direct I/O, I am not sure what dictate how much data
  > to read or write??
  >
  > KC
  >
  

  ---

Connor McDonald
http://www.oracledba.co.uk (mirrored at http://www.oradba.freeserve.co.uk)

"Some days you're the pigeon, some days you're the statue"

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Received on Wed Jun 27 2001 - 10:07:40 CDT