![]() ![]() In this case, we’re looking at the fact that we need to issue sixteen separate operations to read or write 1MiB of data in 64KiB blocks, as opposed to a single operation if we needed to move the same data with blocksize=1M. Similarly, a 64KiB blocksize means a 16x IOPS amplification penalty for 1MiB random I/O. This refers to the fact that the block is the smallest individual amount of data which can be read or written-so a 4KiB operation requires 64KiB of actual data to be read or written. With recordsize=64K or volblocksize=64K, 4K random I/O suffers from an amplification penalty of 16x. When there’s no single storage workload to specifically tune for, we generally recommend a blocksize of 64K-this allows for decent (though not ideal) performance on both throughput-challenged (1MiB random I/O) and IOPS-challenged (4K random I/O) workloads. Generally speaking, you should match your blocksize (volblocksize if using ZVOLs, recordsize if using datasets) directly to your actual workload for the best results. The first of these configuration choices-OpenZFS blocksize-is the most flexible, and the one we devoted the least testing to. Hypervisor storage controller-eg emulated NVMe, emulated SATA/SAS, and VirtIO.Hypervisor storage type-raw device (on ZVOLs) or raw file (on datasets).There are three major categories of storage configuration tunable for virtual machines running atop OpenZFS: OpenZFS is the only back-end storage stack we’ll be testing today-its performance is generally excellent, and its feature set for virtual machine hosting is unparalleled. ![]() When we talk about configuration options that have a massive performance impact, we’re mostly talking about storage configuration-CPU configuration options tend to be fairly straightforward, but storage can be configured with different back-end formats and virtual controllers, which can have a massive impact on both throughput and latency. Today, we’re going to take a look specifically at how bhyve stacks up against the Linux Kernel Virtual Machine-but before we can do that, we need to talk about the best performing configurations under bhyve itself. Not too long ago, we walked you through setting up bhyve on FreeBSD 13.1. ![]()
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