Exadata X4 – Smart Flash Cache Compression – it’s Smart its Flash it’s Compression… So it shall be great, no?
If you take a look at the Datasheet about this new feature you’ll notice something interesting: “zero performance overhead for compression and decompression”. Wow, now its even better! Smart, Flash, Compression, Zero Overhead!
Lets see what more we can find about it:
MOS Doc ID 1571789.1 :
Flash Cache Compression
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. The I/Os to data in flash are orders of magnitude faster than the I/Os to data on disk. The compression and decompression operations are completely transparent to the application and database, and have no performance overhead whatsoever, even when running at rates of millions of I/Os per second. Please refer to and satisfy the additional database licensing requirements listed in the Exadata Licensing Guide before enabling this feature.
Interesting, licenses… after buying Oracle Database, Exadata Hardware, Exadata Storage Server Licenses and now what, More? Seriously?!
It seems that on top of everything you shall buy Advanced Compression Pack. If you take a look at shop.oracle.com you’ll see that the price is more than 10k per CPU socket and a Full Rack of X4-2 have a 16 CPU sockets… Quite a lot, no? Especially after you had just spent a lot, a lot more to get to this point.
But let’s not be pessimistic for the Oracle approach, lets take a look what they actually did. Maybe they had produced massive amount of code, so they shall ask for more:
[root@cell121 ~]# wc -l /opt/oracle/cell/cellsrv/deploy/scripts/unix/hwadapter/diskadp/flash/lsi/set_flash_compression.sh 167 /opt/oracle/cell/cellsrv/deploy/scripts/unix/hwadapter/diskadp/flash/lsi/set_flash_compression.sh [root@cell121 ~]#
Well, apparently no!
When you invoke the alter cell command for enabling the compression,this script is executed. In general the script is just enabling the compression which is implemented on the controller. On the controller! Nothing related with the Database, neither with the Advanced Compression Pack.
This compression is already provided from the hardware. Hardware for which you had already spent a lot of money. It’s just ridiculous.
I’m a huge fan of Oracle Exadata, but for me that’s just a bit too much.