What is I/O Multipath Management…..Why Should I Care?
I/O multipathing is the ability to manage, load balance, and queue up multiple I/O paths in both physical and virtual environments. The problem faced especially with virtual environments is that as the rate of consolidation grows, the efficiency of path management affects both performance and ultimately application availability. Think of your I/O multipath management software as the “traffic cop” that is constantly directing I/O and balancing loads to and from hosts, switches and SAN’s. This job is especially critical in virtualized environments running intensive OLTP (Online Transaction Processing) applications such as SQL Server, Oracle, Virtual Desktop, and Cloud Services. As you add more virtual machines, native multipathing applications have difficulty scaling and this often manifests as latency or outages in the field.
Let me illustrate a “real world” example of a problem that a customer faced. This customer had been experiencing performance issues with a large Oracle environment that had been virtualized. The problems started as an intermittent issue that was causing less than average I/O performance. The customer was having a great deal of difficulty diagnosing the root cause of the problem which was having a negative impact on live production. After examining hardware, switches, and cabling, the problem could still not be found. After all, at times things were running great but then bottlenecks would develop causing latency and temporary “data unavailable” to field offices. This all came to a head one day when the database crashed due to corruption in the tables which was replicated across live production. It ultimately took the customer almost four days to recover the database and restore production. The culprit turned out to be I/O errors which had developed as the paths were being managed using a “round-robin” multipathing method. Unfortunately the multipathing software did not have the intelligence to stop sending I/O down an intermittent path that ultimately went bad. The result was data corruption and a costly outage.
Intelligent Multipathing/Automation vs. Round Robin methods
So how could this disaster have been avoided? Well to give the customer credit, they had done all of the right things configuring their VMware environment as recommended with native multipathing software. The issue is that the software did not have the capability to recognize a failing data path. The software had been configured for a “Round Robin” load balancing method. In this method, I/O’s are sent to the next available path regardless if that path is the “best path”.
The difference between PowerPath/VE and native multipathing is that PowerPath/VE incorporates patented algorithms which “intelligently” direct I/O to the most efficient path, based on diagnostics and testing, instead of just queuing to the next “available” path. The result is higher performance and increased application availability. 1 PowerPath/VE delivers:
• Intelligent multipathing and I/O load balancing
• Seamless path failover and recovery
• Path optimization designed to enhance application performance with EMC VMAX/VNX/VNXe/XtremIO
• Proactive fault detection to prevent interruption to data access
• Reduced complexity and automation: “Set it and forget it” self-management
• End-to-end I/O visibility across the virtual infrastructure
PowerPath/VE Multipathing integrates path testing and diagnostics to “intelligently” send I/O down the best path while routing around flaky or failed paths. It also takes those paths out of the queue and automatically returns those paths to “active” once they are healthy again.
What does “Intelligent I/O Multipathing” do for Performance?
So it’s pretty obvious what a product like PowerPath/VE can do for application availability, but what about performance? After all, one of the main challenges with a highly consolidated virtual environment is the performance degradation that can occur as you scale it up. Another key benefit of PowerPath/VE is the “EMC array performance optimization” that has been designed into its intelligence. PowerPath engineers have optimized the I/O formula to deliver high efficiency on EMC VNX, VNXe, VMAX and XtremIO arrays. This is accomplished by optimizing PowerPath/VE software with the proprietary microcode controlling these arrays. The result has been 2-3 the I/O performance when compared to native mulitpathing. In fact, as seen below, up to a 5X increase in I/O was delivered by PowerPath/VE on EMC’s XtremIO array compared to native mulitpathing.2
Summing “IT” up!
So when it comes to availability and performance, an intelligent I/O multipathing tool like EMC PowerPath/VE maximizes your existing virtual environment by “intelligently” managing and optimizing I/O. The result is maximum I/O performance and increased application availability allowing you to deliver better service through intelligence and automation. The bottom line is that I/O multipath management is critical to your virtual environment, and all management methods and products are not created equally. Spend some time to familiarize yourself with the basics; the data you save could be your own.
1 ESG lab Validation: PowerPath/VE “Automated Path Optimization for VMware Virtual Environments” by Vinny Choinski and Mike Leone
2 PowerPath/VE 5.9 SP1 outperforms VMware NMP with database simulation workload on Jamming tests by 300% to 500% (Jamming test - SAN switch made busy with external traffic)