Re: Is my Oracle Server issuing more IO than it can handle

  • From: Harel Safra <harel.safra@xxxxxxxxx>
  • To: "Amaral, Rui" <Rui.Amaral@xxxxxxxxxxxxxxxx>
  • Date: Wed, 08 Dec 2010 18:41:32 +0200

On 08/12/2010 17:13, Amaral, Rui wrote:
Yes in theory that can be true but it depends on several factors:

Why in theory? Please have a look at a snapshot of statistics from one node of our data warehouse cluster running on EMC DMX4 storage:
*AVG_WRITE_TIME*        *TOTAL_WRITES*  *AVG_READ_TIME*         *TOTAL_READS*
1.1     40460   26.78   35864


Much better write times than read times (the high read time is also contributed from the large IO the database tends to do).

1) assuming write-back caches on the array have not been disabled (which in my 
opinion they should be)
Why do you think write back cache should be disabled? Proper storage systems have sufficient battery backups built in to flush the whole cache to disk in case of power failure.

Harel Safra

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