Yesterday, VMware announced general availability of vSphere 5.5 besides many new things. The list of what is new in this release of ESXi is long but I want to mention two specific ESXi Hypervisor enhancements; Support for Reliable Memory Technology and Hot-Pluggable PCIe SSD Devices.
Support for Reliable Memory Technology
What VMware calls Reliable Memory Technology is otherwise known as Fault Resilient Memory in PowerEdge servers. Basically, the system firmware configures a region of system memory as fault resilient and communicates information about it to the OS. The ESXi Hypervisor uses this information to optimize the placement of the VMkernel and other critical components in the fault resilient region of the system memory — making the hypervisor robust against memory errors. At this time it appears that Dell PowerEdge servers are the only systems that can take advantage of this new ESXi enhancement.
Hot-Pluggable PCIe SSD Devices
Dell and Micron worked closely with VMware on this feature. Now we can hot-add or hot-remove a Dell PowerEdge Express Flash PCIe SSDfrom a Dell server running vSphere ESXi 5.5, just like a SAS HDD. The PCIe layer code of ESXi is enhanced to handle surprise removals and insertions of PCIe devices. The device driver structure was also impacted to handle these events. A hot-removal leads to a permanent device loss (PDL) condition in VMware terms. PDL AutoRemove is a related enhancement also introduced in this release. PDL AutoRemove works only if there are no open handles left on the device. We still see the same storage stack restrictions in case of unplanned PDL that has been there with SAS and FC storage. VMware has multiple KB articles covering this topic of planned versus unplanned PDL.
Looking at PCIe SSDs available, in market and servers supporting them, it seems currently only Dell PowerEdge servers can take advantage of this new vSphere 5.5 enhancement. Later during day-1 of VMworld 2013, we talked about this feature in a breakout session titled: Low Latency, High Bandwidth and Now Hot-Pluggable: PCIe SSDs Are Enterprise Ready. Co-presented by Ahmad Ali of Dell and Dave Edwards of Micron.
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