Even if you have a fast array and storage network, and you are still experiencing high storage latencies for your high throughput VMs, it might be because of choked Queue Depths at the VM and virtual LUN device in the host. This problem will happen only if a few VMs…
VMware’s Storage Architecture
VMware has two categories of SSD Host Caches — those that swap out memory contents to SSD when host memory is full, and those that cache storage requests to host Flash / RAM. In the former category are the below VMware features. VMware’s ‘Host Cache Configuration’ feature VMware’s ‘Virtual Flash…
By caching all writes from VMs to VMware host SSD or RAM, VirtuCache reduces write latency for VMs that are deployed in a VMware Metro / Stretched Storage Cluster (vMSC), and eliminates latency of the WAN link from factoring into VM latencies, thus improving the performance of VMs however slow…
Even when Ontap Select is using high-performance enterprise SSDs, it shows high latencies because there are quite a few file system layers that the storage IO must traverse. Within Ontap Select, you first create a separate VMFS Datastore on each locally attached SSD or HDD on each host in the…
Back when I founded Virtunet in 2010, VMware VSAN had started to effectively compete with SAN arrays. The appeal of hyperconverged infrastructure was obvious, getting rid of a separate storage appliance and having Flash memory right on the VMware host was the highest performing storage configuration. For a small 3-4…
The quickest to find out if you have storage performance issues in ESXi is by doing SSH (use putty) to the ESXi host and typing the command ‘esxtop’ and then typing the letter ‘v’.
Typically, you would want to improve both read and write latency in VMware. But if your VM write latency is already quite low and it is only your read latency that is high, then it is understandable that you would want to improve only disk read latency in VMware. Improving…
If you have high disk IO write latency in VMware at the VM, Datastore, or Device level, then you could fix this issue in either of three ways – tinker around the edges in VMware, get a fast storage array and network, or use host side cache.
Storage IO path in VSAN and VirtuCache is similar to a large extent since both service storage IO from in-VMware host media. Though with VirtuCache, storage latency is lower than with VSAN for four reasons: Reads are always serviced from local cache media in VirtuCache. In VSAN there is a…
VMware has discontinued VFRC in ESXi 7.x 0 Despite the end-of-life for VFRC, if you still want to review the differences between VFRC and VirtuCache, below are the four most important ones. We cache reads (‘Write-Through’ Caching) and writes (‘Write-Back’ Caching), VMware’s VFRC caches only reads. We improve the performance…