VirtuCache is installed in VMware vSphere kernel. It then automatically caches frequently and recently used data from any backend storage to any high speed media (RAM/SSD) in the VMware host. By bringing large amounts of 'hot' data closer to the VMware host GPU and CPU, VirtuCache improves the performance of all applications running within VMs including GPU assisted operations.
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 are behind the network and storage controller.
High write latencies in a stretched SAN cluster
Tourbillon Capital Partner is a hedge fund. They run proprietary trading software within VMware VMs that requires under 5 millisecond latencies. Tourbillon has two VMware clusters with a few nodes in each cluster. Each ESXi cluster is connected to a Pure Storage SAN array. Both ESXi clusters are in different datacenters, but connected to each other over a 10gbps WAN link. A stretched SAN cluster across these two ESXi clusters is created using Datacore software. Simply speaking what the Datacore stretched cluster accomplishes is that all VM writes are synchronously written to both Pure Storage arrays - the array that’s in the same datacenter as the VM, and also to the remote Pure Storage array. In this way Tourbillon’s IT folks assure themselves of seconds-to-minutes RPO and RTO time in case of a datacenter outage.
The problem with this architecture was that sometimes VM write latencies exceeded the 10ms ceiling that was required by their trading application. This was because writes had to go over their WAN link between datacenters. Even though the WAN link was 10gbps, it would spike to > 5ms latencies from time to time. Typically, the standard deviation for latencies in a long distance WAN link is quite a bit more than in shorter LAN links of the same speed.
Caching VM writes to in-host RAM reduced write latencies considerably
Tourbillon deployed VirtuCache to fix this issue. VirtuCache was installed in every host, in both ESXi clusters. It was configured to cache reads and writes to in-host RAM, with the write cache replicated to another host in the same datacenter, which in turn resulted in sub-millisecond VM write latencies at all times. In this way, VirtuCache effectively papered over the underlying high WAN latencies, when large volume of writes were transmitted from VMs.
Creation Museum in Kentucky, USA is a museum about Bible history and creationism. Their storage needs were typical of a museum, requiring large amounts of storage for digital multimedia content related to the various exhibits at the museum.
The Ark Encounter, in Williamstown, Kentucky, features a full-size Noah’s Ark built according to the dimensions of the Bible. Answers in Genesis (AiG) is the Christian ministry responsible for The Ark Encounter.
AiG's IT department had a few ESXi hosts connected to their HP Store VSA. As a result of increased attendance at the Ark, their VMware workload increased dramatically, which in turn resulted in performance issues within VMs.
AiG turned to VirtuCache to mitigate their storage latency issues. By caching frequently and recently used data (both reads and writes) to in-host SSDs+RAM, Virtunet resolved their storage performance issues. We competed with HP Store VSA's Adaptive Optimization(AO) feature, which is HP's tiering functionality for the VSA.
Here is how VirtuCache competes with the Store VSA's tiering functionality.
CEPH storage from Virtunet has all the features of traditional iSCSI SAN with the exception that it is reasonably priced because it uses commodity servers with all off-the-shelf hardware. And so it is ideally suited for backup and DR storage which needs to be cheap above all else.
By improving storage performance, Virtucache was able to improve the performance of Jenkins based Continuous Integration process, which in turn resulted in quicker build-test cycles.
Microsoft Dynamics AX transaction processing is write intensive and its reporting is read intensive, thus putting pressure on customer's existing storage infrastructure. By caching frequently used data from customer's existing storage to in-host SSDs, VirtuCache was able to reduce read and write latencies for AX running within VMware VMs.
EMC Fast Cache Storage Controller Based Caching for VNX Appliances versus VirtuCache Host Side Caching for Any SAN based Appliance
In case of FastCache or any storage appliance based caching, the SSD is more expensive than if the same SSD were bought retail. Also the SSD performs better in the host than in the storage appliance, since the SSD in the appliance is constrained by the network and controller.
EMC FastCache is SSD based caching functionality sold by EMC for their VNX appliances. It tiers frequently used data, mainly reads, to SSDs in the appliance from slower HDDs on the appliance.
VirtuCache is software sold by Virtunet (and competing with EMC's FastCache) that is installed in the VMware kernel along with a SSD in the same VMware host, and it caches frequently and recently used data, both reads and writes, to the in-host SSD from any SAN based storage appliance.
This blog article lists the differences between VirtuCache and EMC's FastCache.
VirtuCache accelerates storage appliances to the same extent regardless of whether they have faster SAS hard drives or slower SATA drives, and regardless of the age and speed of SAN. Thus we help postpone a SAN upgrade, or if the customer is looking at a capacity upgrade, selecting an appliance with cheaper SATA hard drives would suffice. We save them capex dollars either way.
By improving storage performance for VMs, host side caching facilitates P2V of IO intensive bare-metal servers. And it saves capex because there is no storage upgrade involved.
If you have not yet virtualized your physical servers due only to perceived storage performance issues in VMs, then deploying VirtuCache will help. Since VirtuCache caches frequently used reads and all recent writes to in-host SSD and/or in-host RAM, from any back-end storage appliance, the storage performance from within a VM will now be considerably higher than from within your existing physical Linux or Windows server. As a result, P2V of database servers and other storage IO intensive applications is a big use case for VirtuCache.
This blog article talks about how to assure yourself BEFORE you do the P2V that the VirtuCache accelerated storage + VMware infrastructure will perform better than your existing bare-metal servers.
Also a customer use case illustrates that VirtuCache accelerated bare-metal server (when VirtuCache is deployed in bare-metal Linux) performs at the same level as VirtuCache accelerated VMware VM (when VirtuCache is installed in the VMware kernel), thus proving that virtualization in itself does not reduce application performance.