RE: Is my Oracle Server issuing more IO than it can handle
Date: Thu, 9 Dec 2010 09:14:43 -0500
Message-ID: <1B861F1ABE40A84AA92AD585B20C558B26E4E11D22_at_EX7T2-CV06.TDBFG.COM>
Power failure is not the only thing can affect disk caches and yes my previous company had it happen during a patch on the array gone bad.
I agree you're numbers are good but I have had it the other way around.... now I do admin maybe because not everyone was on the same page in configuring it because it was a shared resource with different demands on the array.
Rui Amaral
Database Administrator
ITS - SSG
TD Bank Financial Group
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Toronto, ON, CA, M5K1A2
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From: Harel Safra [mailto:harel.safra_at_gmail.com] Sent: Wednesday, December 08, 2010 11:42 AM To: Amaral, Rui
Cc: 'Oracle Dba Wannabe'; niall.litchfield_at_gmail.com; okh_at_oraconsult.de; oracle-l_at_freelists.org Subject: Re: Is my Oracle Server issuing more IO than it can handle
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).
- 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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