Archive: Posts

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 in CEPH OSD servers, whether for caching / journaling or primary storage, are not very effective from a performance point of view. 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 when connected to ESXi hosts, and its solution. There are two options for improving the performance of...

Infinio’s Read Caching versus Virtunet’s Read+Write Caching Software

The biggest differences are: Virtunet's VirtuCache accelerates reads and writes. Infinio Accelerator accelerates only reads. Infinio doesn't support Linked Clones or Instant Clones, hence VDI is not supported. We support all VDI features in VMware Horizon and Citrix Xendesktop. With us you can apply caching policy at the datastore and/or VM level versus only at the VM level with Infinio. Infinio doesn't accelerate IO that originates in the VMware OS. VirtuCache accelerates all storage...

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...

CEPH Storage with Server Side Caching for Genomics

March 7, 2019:

As it relates to storage, genome sequencing workflow has two requirements.

  1. Need for cheap ($/GB) Petabyte scale storage.

  2. Need for faster processing of Genome files under analysis, many of which are a few hundred GB in size.

Reducing Build Times for DevOps

April 12, 2018: 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...

VirtuCache on ESXi 7, accelerating Netapp Ontap Select Storage

April 15, 2020:

City of Mountain View is using VirtuCache to improve the performance of Netapp's Ontap Select storage software. They were one of our first customers to upgrade to ESXi 7.0 and so they had to upgrade VirtuCache as well.

We announced General Availability of VirtuCache for ESXi 7 within 2 weeks of VMware's ESXi 7 release date.

Reducing write latencies in a VMware stretched SAN cluster

October 12, 2018: 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...
Page 1 of 3123