In many of our presentations we have a slide or two related to Moore’s Law. The following quote is from Wikipedia:

 

“Moore’s law is the observation that, over the history of computing hardware, the number of transistors on integrated circuits doubles approximately every two years.”

 

The doubling of CPU performance approximately every two years has benefited databases both in terms of speed and cost. In the picture below we show the ‘gap challenge’ as storage performance hasn't doubled every two years.

Performance Gap.png

 

In many of my customers’ interactions rarely is CPU the bottleneck however the storage performance gap means Oracle DBAs are looking for solutions to improve the I/O response times for their databases. Looking to improve performance of part of the system generally relates to Amdahl’s law:

 

“…is used to find the maximum expected improvement to an overall system when part of the of the system is improved.”

 

This quote from the research article entitled, An Efficient Schema for Cloud Systems Based on SSD Cache Technology pulls the concepts together:

 

“For some applications which have quite high requirements on response time, simply to improve CPU performance cannot improve the overall performance of a system: hence, it is necessary to improve the I/O performance and reduce the speed difference between storage system and CPU.”

 

Oracle database(s) fall into the category of high requirements on response time with the goal of reducing the speed difference between storage system and CPU. In the research article mentioned above the characteristics of caching technology are:


  • Goals placing frequently accessed data in fast accessing device, speeding up the access and reducing latency time [4]
  • Most of the current caching algorithms take into account locality of reference and accessing frequency [3]

  

The strength of solid-state drives, commonly called flash drives, is they can be used to significantly improve I/O performance. EMC has two proven technologies that reduce the speed difference between the storage system and CPU:

 

  • Fully Automated Storage Tiering Virtual Provisioning (FAST VP) is available on both the VMAX and VNX storage arrays and identifies frequently accessed data for promotion to Flash drives. Employing the principle of locality of reference and frequency of access enables the intelligent movement of hot blocks from high capacity drives to much lower latency Flash drives.
  • FAST Cache on the VNX similarly identifies the frequently accessed data and copies the hot blocks to the Flash drives. The ‘copy’ part is the differentiator as the original block remains on the high capacity drives. By coping the hot blocks to Flash drives read performance is accelerated.

 

Caching technology is challenged in situations that involve access to blocks not frequently accessed and therefor not in cache but require the same level of performance.  The seldom accessed low latency data requirements occur when a report is only run once a week or end of month activities that is outside of the cache’s pool. Unfortunately, this could mean a report that needs to take less than 10 minutes might take significantly longer. The question is how do we solve this Caching technology challenge and meet the requirements of seldom access low latency data requirements?


An all flash drive array like EMC’s newly released XtremIO offers low latency across both types of data: frequently access (cache friendly) and seldom access (cache challenged). Because all the data will reside on Flash drives performance predictability is improved and often is in the sub-millisecond latency range. XtremIO is targeted at mission critical databases and applications that require extreme performance as the loss of milliseconds can mean loss of profit to the business. I’m including a link to the XtemIO data sheet for Oracle DBAs and everyone who have mission critical applications requiring all Flash performance.

 

The XtremIO storage does take into account the difference in performance between reads and writes based on flash drives. If you are interested in how this works please comment below or want another topic I’ll be interested to read your ideas.

 

References:

  1. Moore’s Law on Wikipedia
  2. Amdahl’s Law on Wikipedia
  3. An Efficient Schema for Cloud Systems Based on SSD Cache Technology, a research article by Jinjiang Liu, Yihua Lan, Jingjing Liang, Quanzhou Cheng, Chih Cheng Hung, Chao Yin, and Jiadong Sun
  4. Optimal Multistream Sequential Prefetching in a Shared Cache, ACM Transactions on Storage, vol. 3, no. 3 article 10, 2007

 

XtremIO Links:

 

Want to find out more, visit any EMC Forum. There are a few left this year:  http://emc.im/EMCForum2013