RE: Virident FlashMAX SCM

  • From: "Goulet, Richard" <Richard.Goulet@xxxxxxxxxxx>
  • To: "anthony.ballo@xxxxxxxxxxx" <anthony.ballo@xxxxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 6 Jun 2012 15:01:37 +0000

Darn that myth is still running around?  No you're not missing anything, but 
the author certainly is.  Goes along with the individual who told me that you 
can drop the system tablespace.  Yes you can, but your db crashes in about 0.5 
mseconds thereafter.

Richard Goulet
Senior Oracle DBA/NA TEAM Lead
PAREXEL International
T 978.495.4127
 
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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Anthony Ballo
Sent: Tuesday, June 05, 2012 2:59 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Virident FlashMAX SCM

Was reading this white paper from Virident today:
Accelerating Oracle Databases and Reducing Storage Complexity and Costs. 
Virident FlashMAX SCM as Primary Storage.


Offered at: 
http://www.bitpipe.com/data/document.do?res_id37280483_183&srcP53040&asrc=EM_BRU_17570135&uid956921


They are making a point that switching from 8k block size to 4k would reap 
performance benefits:


When Oracle data is stored on FlashMAX devices, reducing Oracle database block 
size from the default value of 8192 bytes (8KB) to 4096 bytes (4KB) can provide 
substantial performance benefits in many applications. With HDDs, 
reading/writing 4KB takes essentially the same amount of time as 8KB as most of 
the time is spent on moving heads. In contrast, FlashMAX can perform 2x the 
amount of IOPS with 4KB block size compared to 8KB block size, or the same 
amount of IOPS at lower latencies.


They offered the steps on how to change your block size:

You can set this parameter in several different ways:

 1.  By adding it to initORACLE_SID.ora file (or changing if the parameter 
already exists)  2.  By setting the parameter in the SPFILE:
    *   SQL>alter system set db_block_size@96 scope=spfile;
    *   SQL>shutdown immediate
    *   SQL>startup
 3.  By setting it on Initialization Parameters -> Sizing tab of the DBCA

Last I checked, you could only change the default block size at DB creation. 
Sure you can have multiple block sizes supported at the Tablespace level (must 
also specify cache sizes) but it's not as simple as changing a init parameter 
and bouncing your instance - otherwise, you will see:

ORA-00209: control file blocksize mismatch, check alert log for more info

Hard to take this white paper seriously or am I missing something?


Anthony




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