In all likelihood, companies looking to use virtualization to consolidate servers will still see some contention for disk resources, regardless of whether data resides on the server or a SAN. Say you consolidate multiple file and print servers on a single box using VMs and store the files in the VM or store all the data from all the servers on a single SAN. In either case, the VMs will be accessing the data from the same shared resource.
The performance overhead of virtualization can be viewed against two basic assumptions: IT is going to use virtualization to fully utilize servers the company owns, or a company is looking to consolidate existing servers onto newer hardware. For the purposes of baseline testing, we used the former assumption of maximizing server utilization.
Under the full-utilization scenario, IT divides up memory, in theory because existing memory isn't being fully used. Say you notice that an application running on dedicated hardware uses only part of the memory and processing capacity of that server--perhaps 512 MB out of 2 GB and 25 percent of 2.8 GHz. Migrating this application to VMware's ESX Server lets you dedicate that 512 MB and 700 MHz to the application and still have memory and processing power available. Therefore, in our tests, we divided our 2 GB of memory based on the needs of the applications running on the VM instances. SQL Server requires a minimum 1 GB of RAM, for example, while Exchange Server 2003 will run with 512 MB of RAM.
VMware has memory-page sharing technology that lets IT overcommit physical memory for VMs. This memory-page sharing lets VI3 allocate at least twice as much virtual memory as there is physical memory when running the same OS on VMs running on the same hardware. This is useful in situations in which you want to consolidate a number of low-use apps, such as file and print services, running on individual servers. A single server could run a dozen VMs because the likelihood of all these systems requiring processing power and memory at the same time is small, and even when requests exceed resources, slowed performance wouldn't be an issue.
Architecturally, VMware's ESX Server 2.0 uses a stripped-down version of Linux to host VMs, then abstracts each VM's hardware through a common virtual BIOS and virtual hardware drivers. In our initial tests, we measured the performance costs of these two layers, but also factored in less memory being available to each virtual machine; ESX Server requires roughly 200 MB of memory.
Bob Friday, Chief AI Officer for Juniper Networks, explains how the advanced technology is transforming operations.
Contact center leaders from 8x8, Awaken Intelligence, and 360insight discuss the importance of agent experience.
AI may force enterprises to rewire parts of their data centers so they are fully optimized to run such workloads. The question is do you use Ethernet or InfiniBand?
