Re: Exadata Cacheflash Compression

That made me to ask  one more question:  The above MOC Doc saying 

Flash cache compression dynamically increases the logical capacity of the flash cache by transparently compressing user data as it is loaded into the flash cache. This allows much more data to be kept in flash, and decreases the need to access data on disk drives.


 
So, it is increasing the logical capacity of the flash cache by  transparently compressing the user data and never said the capacity is getting doubled.  So, are we really right to say that my 20TB FC will be 40TB after compression  or only store the data compressed so that I can store more?  Also, how can I see the current FC is compressed or not?

Thanks,
Thomas
On Friday, May 9, 2014 6:53 PM, Craig Dickman <dmarc-noreply_at_freelists.org> wrote:
 
As Carol said, you're correct.  I should have been more specific.


________________________________
 From: George Leonard - Business Connexion <George.Leonard_at_bcx.co.za>
To: "dmarc-noreply_at_freelists.org" <dmarc-noreply_at_freelists.org> 
Cc: ORACLE- L <oracle-l_at_freelists.org>; Roy <royxavier_at_yahoo.com> 
Sent: Friday, May 9, 2014 4:29 AM
Subject: Re: Exadata Cacheflash Compression
 


Hi Craig 

You say with X4... is this not a way of behaviour thats associated more with a SW release number, compared to a HW model/range?




Yours Sincerely

________________________________________ 
George Leonard
Oracle Engineered System Specialist

Mobile: +27.82 655 2466
eMail: george.leonard_at_bcx.co.za
Web: http://www.bcx.com
   

On 08 May 2014, at 5:26 PM, Craig Dickman <dmarc-noreply_at_freelists.org> wrote:

Here's how I understand it.  The data in flashcache is compressed by default anyway, it happens automatically.  Prior to X4, the data in the flashcache would get compressed but the extra space made available by this compression was not usable.  
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>With the release of X4, Oracle gives you the ability to enable flashcache compression which essentially gives you the ability to use the space freed up by the automatic flashcache compression.  Basically, you turn 20TB of flash cache into 40TB usable if you have Advanced Compression.
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>________________________________
> From: Thomas P S <dmarc-noreply_at_freelists.org>
>To: ORACLE- L <oracle-l_at_freelists.org>; Roy <royxavier_at_yahoo.com> 
>Sent: Thursday, May 8, 2014 6:29 AM
>Subject: Exadata Cacheflash Compression
>
>
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>Dear List,
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>We have X4-2 Half Rack with 20TB flash cache with database size 8TB.  I am very reluctant to enable flashcache compression as the size of the database is half of flashcache, but Oracle says enabling flashcache compression is a best practice.  Every code execution need time, even though FC is implemented in hardware level compression, still I believe, there will be a penalty.  In this scenario, enabling flashcache compression is a wise idea?   Any one got  falshcache I/O performance test results with compression and with out? 
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>Note: License is not an issue as we have Advanced Compression license.
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>Thanks in advance,
>
>Thomas Saviour
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