Why are Write Latencies High Even When the EMC Unity Appliance has Plenty of System Cache Memory and Fast Cache SSDs?
If you are experiencing high write latencies in VMs when using an EMC Unity Hybrid array, it could be because the caching and tiering solutions in Unity don’t cache random small block writes, and your applications might be generating large volumes of such storage IO.
View Storage Accelerator vs. VirtuCache – VMware Host Side Storage Caching
The big difference between the two is that VSA caches only 2GB of reads from the Master VM1,2. VirtuCache caches reads + writes from all server & desktop VMs, and it can cache to TBs of in-host SSD/RAM, so that all storage IO is serviced from in-host cache.
More details in the table below.
To Improve CEPH performance for VMware, Install SSDs in VMware hosts, NOT OSD hosts.
SSDs deployed for caching in CEPH OSD servers are not very effective. The problem lies not in the SSDs, but because they are deployed at a point in the IO path that is downstream (in relation to VMs that run user applications) of where the IO bottleneck is. This post looks at this performance shortcoming of CEPH and its solution.
There are two options for improving the performance of CEPH.
Option 1 is to deploy SSDs in CEPH OSD servers for journaling (write caching) and read...
How to Select SSDs for Host Side Caching for VMware – Interface, Model, Size, Source and Raid Level ?
In terms of price/performance, enterprise NVME SSDs have now become the best choice for in-VMware host caching media. They are higher performing and cost just a little more than their lower performing SATA counterparts. The Intel P4600/P4610 NVME SSDs are my favorites. If you don’t have a spare 2.5” NVME or PCIe slot in your ESXi host, which precludes you from using NVME SSDs, you could use enterprise SATA SSDs. If you choose to go with SATA SSDs, you will also need a high queue depth RAID...
Infinio’s Read Caching versus Virtunet’s Read+Write Caching Software
The biggest differences are:
We accelerate both reads and writes, Infinio accelerates only reads.
Infinio doesn't support Linked Clones or Non Persistent VDI. We support all VDI features.
With us you can apply caching policy at the datastore and/or VM level versus only at the VM level with Infinio.
We accelerate IO originating in VMware kernel and VMs, versus only VM generated IO is accelerated by...
Virtunet Read + Write Caching Versus Datrium Read Only Caching, Part II.
In our first article, we explained the differences between our host side caching software (VirtuCache) and Datrium's (DVX DiESL). To summarize the first article, VirtuCache differs from DVX DiESL in 3 ways - (1) VirtuCache caches reads and writes to in-host cache media, Datrium caches only reads; (2) DVX DiESL only works for Datrium's own appliance, VirtuCache works for any appliance; and (3) VirtuCache can cache to in-host RAM and SSD, DVX DiESL can cache to in-host SSD only.
Now Datrium, on...
In-VMware Host Caching – Datrium’s Appliance Specific Host Cache Versus Virtunet’s Host Cache for Any Storage.
Both Datrium and us differentiate from the rest of the storage appliance vendors in that both of us cache data to cache media in the VMware host instead of the storage appliance, which is the traditional approach.
But the similarities between Datrium's and our ESXi host cache end there. The top three differences between Datrium DVX DiESL and our VirtuCache are:
Our host side caching accelerates any storage appliance, Datrium’s works only for their own appliance;
We cache...
Reducing Build Times for DevOps
ServiceNow's Itapp Dev/Ops team wanted to improve storage performance from their existing HP 3PAR storage appliance and iSCSI storage network without requiring a hardware refresh.
VirtuCache Deployment: Virtucache was installed on 3 ESXi hosts caching to 1.6TB PM1725 PCIE flash cards. In our tests the PM1725 SSD did 250MBps at 1ms VM level latencies.
VirtuCache was configured to cache both reads and writes for all VMs (Write-Back caching). Writes were replicated to another SSD on another...
Reducing write latencies in a VMware stretched SAN cluster
There are only a few applications, financial trading software being one example, that require very low latencies, lower even than what’s possible with an all-flash array (AFA). VirtuCache caching to in-host RAM results in lower VM latencies than an AFA. This is because RAM latencies are an order of magnitude lower than NVME SSDs, and in the case of VirtuCache the cache media (RAM) is connected to the host CPU through a high speed memory bus, versus in the case of an AFA where the NVME SSDs...
VMware SSD and RAM Cache for Dell VRTX
Dell's PowerEdge VRTX hyper-converged appliance can either have all hard drive datastores or all SSD datastores, but you can't have SSDs act as tiering or caching media for VRTX volumes. That's where VirtuCache comes in.