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Can I improve VM performance with flash tiering?

Physical RAM and flash storage are traditional ways to improve VM performance. But the addition of mixed flash holds promise.

I haven't seen a significant adoption of tiers consisting of memory flash and solid-state drive flash. But I do think simultaneous usage of multiple flash types will increase, especially for virtualization hosts.

The primary goal for any virtualization administrator is to ensure the performance of virtual machines (VMs). Traditionally, this has meant provisioning the VM with plenty of physical RAM and using flash storage. However, mixed flash has the potential to further improve VM performance.

One factor that can affect VM performance is the Windows pagefile within the guest OS. Pagefile originated at a time when physical RAM was expensive, and even today it is used to make up for shortages in physical RAM.

Mixed flash has the potential to further improve VM performance.

Because paging involves committing memory pages to disk storage, it can greatly affect the performance of VMs. For physical servers, admins have long tried to provision the server with enough physical memory to minimize paging. This approach isn't always practical for VMs because committing large amounts of RAM to a VM decreases the VM density of the host. As such, virtualization admins have often tried to move the pagefile to an isolated storage location where it will not interfere with regular storage I/O.

More recently, memory channel flash has emerged as a good option for VM OS paging. Some organizations have had success using memory flash as a small VMware data store exclusively for guest OS paging. The virtual hard disks and other VM components continue to reside on a flash array as usual. This approach can improve overall VM performance by greatly enhancing the speed of guest OS paging operations without committing excessive RAM to the VM.

Next Steps

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This was last published in April 2015

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Are you using multiple flash types to improve VM performance? How is it working?
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In other words, increase the memory to reduce the incidence of thrashing?
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