Re: 11gR2 smart flash cache
- From: Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx>
- To: steve.harville@xxxxxxxxx
- Date: Wed, 12 Jan 2011 16:35:57 -0600
One quick note on this... direct reads do not always indicate temp (or
even parallel). In 11g Oracle will sometimes start using direct path
reads for serial full tablescans.
I recently observed this happening a lot with one of my clients. FYI, I
believe that this particular database had an underconfigured SGA...
might be related. Interestingly, because Oracle was doing so many FTS
with direct path, the BCHR looked deceptively healthy.
-Jeremy
Steve Harville wrote:
> I have not tried this setting but I do have some experience with
> Oracle on flash drives.
> We are an EMC shop so most I/O is already cached (all writes and all
> sequential reads). The system cannot cache random reads so that is
> where I use flash drives. The temp tablespace can benefit the most
> from flash drives since it exhibits this read pattern. If "direct
> reads" are a large part of your total wait time then you can probably
> benefit from moving temp to flash.
>
> Steve Harville
>
> http://www.linkedin.com/in/steveharville
>
>
>
> On Wed, Jan 12, 2011 at 5:24 AM, Zhu,Chao <zhuchao@xxxxxxxxx> wrote:
>
>> hi, List friends,
>> Oracle has been promoting this flash cache as second tier cache for
>> oracle for a while; Just wondering whether anyone has used this within the
>> industry?
>> We typically have 30gb-60gb SGA supporting 1TB-4TB database; We found
>> usually 30gb or 60gb cache size does not really matter much for majority of
>> our database(some has big diff though, depends on workload profile/active
>> dataset); But a 300gb flashdisk might make huge difference, and help reduce
>> the IOPS load on the SAN side?
>>
>> Looking forward to industry experience;
>>
>> Thx
>>
>>
>>
>> --
>> Regards
>> Zhu Chao
>>
--
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Jeremy Schneider
Chicago
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