Yellow Bricks

by Duncan Epping

performance

Disk latency and esxtop

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We just had a very good and interesting VMTN Podcast on virtualized MS SQL performance and best practices. One of the questions was about disk performance. Hemant Gaidhan talked about esxtop and how to discover possible performance issues, and specifically mentioned latency. I’ve never really looked into this section of esxtop and did a quick search and of course the “Interpreting esxtop Statistics” answered which counters to watch and what each counter represents:

Section 4.2.2 Latency Statistics
This group of counters report latency values measured at three different points in the ESX storage stack. In the context of the figure below, the latency counters in esxtop report the Guest, ESX Kernel and Device latencies. These are under the labels GAVG, KAVG and DAVG, respectively. Note that GAVG is the sum of DAVG and KAVG counters.

I recommend reading the rest of the 4.2.2 section to anyone looking for more indepth info on esxtop and storage performance. Also read page 14/15 of Hemant’s document on SQL Server performance/best practices. Another great read and tip from Hemant was the “Scalable Storage Performance” whitepaper.

mbrscan, mbralign and RCU

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A while back I wrote an article on checking your disk alignment and even changing the disk alignment from the service console. Since then a lot of people asked me for the exact link, because I don’t have a now.NetApp.com account I wasn’t able to provide it. Today I received an email from the developer, Eric Forgette, with a link to a community article which contains links to both tools, mbralign and mbrscan.

Eric is also the one who developed RCU(Rapid Cloning Utilities). I just watched the demo video on youtube. In short: It’s a vCenter pluging which enables you to deploy hundreds of VDI desktops by utilizing the capabilities of the array. Keith Aasen wrote a blog article on this plugin which has some more details. I guess with the vStorage API coming up we can expect more vendors to add storage capabilities to the vCenter GUI, think snapshots / clones and more…

Pluggable Storage Architecture, exploring the next version of ESX/vCenter

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The next version of ESX has a totally different architecture for storage. The new architecture is called “Pluggable Storage Architecture”. For my own understanding I wanted to write down how this actually works and what all the different abbreviations/acronyms mean:

  • PSA = Pluggable Storage Architecture
  • NMP = Native Multipathing
  • MPP = Multipathing Plugin
  • PSP = Path Selection Plugin
  • SATP = Storage Array Type Plugin

At the top level we have “Pluggable Storage Architecture”. This is just the name of the new concept, but it’s a well chosen name cause that’s what it is… a new storage architecture that uses plugins. Let’s start with the native VMware plugins. [Read more…] about Pluggable Storage Architecture, exploring the next version of ESX/vCenter

iSCSI multipathing with esxcli! Exploring the next version of ESX

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In the “Multivendor post to iSCSI” article by Chad Sakac and others(Netapp, EMC, Dell, HP, VMware) a new multi-pathing method for iSCSI on the next version of ESX(vSphere) had already been revealed. Read the full article for in depth information on how this works in the current version and how it will work in the next version. I guess the following section sums it:

Now, this behavior will be changing in the next major VMware release. Among other improvements, the iSCSI initiator will be able to use multiple iSCSI sessions (hence multiple TCP connections).

I was wondering how to set this up and it’s actually quite easy. You need to follow the normal guidelines for configuring iSCSI. But instead of binding two nics to one VMkernel you create two(or more) VMkernels with a 1:1 connection to a nic. Make sure that the VMkernels only have 1 active nic. All other nics must be moved down to “Unused Adapters”. Within vCenter it will turn up like this: [Read more…] about iSCSI multipathing with esxcli! Exploring the next version of ESX

Whitepaper: Performance Evaluation of AMD RVI Hardware Assist

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I recently discussed the effect of RVI/Virtualized MMU on Transparent page Sharing, and just 5 days later VMware published this extensive PDF:”Performance Evaluation of AMD RVI Hardware Assist“.

AMD recently introduced its second generation of hardware support for virtualization, incorporating MMU virtualization called Rapid Virtualization Indexing (RVI). Hardware support for MMU virtualization can improve performance, particularly for MMU-intensive workloads.

VMware ESX 3.5 leverages this RVI support in AMD processors. This paper compares the performance with and without RVI of a number of industry-standard benchmarks and microbenchmarks running in VMware ESX 3.5, Update 2 on AMD Opteron 8384 (“Shanghai”) processors.

Read the PDF for more indepth info, but I think the most important bit is:”The improvement provided by RVI increases with larger numbers of vCPUs; in the four vCPU case RVI performed 42% better than BT.” And that’s just for one of the benchmarks. If you’ve got an AMD processor or Intel Processor that supports virtualized MMU, be sure to do a benchmark and it probably will be beneficial to turn it on.