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.
Go with enterprise grade and not consumer grade SSDs. And deploy the SSD behind a good Raid controller (queue depth > 128). Samsung SM863 and Intel S3710 are good choices. The SM863 is better value for money. Also, don't skimp on the Raid controller since you don't want it to choke before the SSD does.
Though this article is in the context of using SSDs with VirtuCache (our Host Side Caching software for VMware that improves the performance of any SAN based storage appliance), these principles apply to the larger category of host side storage software.
This blog article will cover the below topics
- Select SSD type - SATA, SAS, OR PCIe?
- Size the SSD?
- How many SSDs are needed in a VMware Host and across the VMware cluster?
- The need to locally RAID the SSD?
- Where to buy the SSD from?
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.
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.
Virtunet’s Write-Back (Read+Write) Caching Competing with Write-Through (Read-Only) Caching at a Large School District
Host side caching software needs to accelerate both reads and writes especially in light of increasing competition from all-flash arrays. Caching writes is important even for workloads that are read intensive. If we were not to accelerate writes, the reads behind the writes on the same thread will not be accelerated, thus slowing reads as well.
Using TPC-C benchmark, we showed 2x improvement in performance versus a read caching software vendor at a large district.
Typically Hadoop workloads are run on bare-metal servers. However since Stanford’s School of Medicine was 100% virtualized, and because their security, monitoring & management tools were integrated within VMware, it was easier for them to deploy Hadoop within VMs, instead of provisioning new physical servers.
The biggest challenge Stanford faced with Hadoop VMs was low throughput and high latencies for writes to disk.
Deploying VirtuCache resulted in write latencies in Hadoop reducing to an eighth of what they were before.
EHR, imaging, analytics, desktop & application virtualization applications are prone to storage performance issues in VMware, that are easily solved with VirtuCache.