InfoWorld review: Dell R815 server makes heavy virtualization light on the wallet
The Dell PowerEdge R815 and its four 12-core AMD Opteron CPUs want to run many, many virtual machines, at a much lower cost than Intel multicoreFollow @pvenezia
How many single-purpose workloads can make effective use of a box of this size? Not many. Heavily threaded applications, big database workloads, and data warehousing builds fit the picture, but a fully loaded R815 isn't likely your first choice for a Microsoft Exchange server or Web server. However, the R815 most certainly is a box you'd want to use to run a ton of virtual servers on.
Virtualization hammers RAM, I/O, and CPU, in that order. Most virtual machines in most VMware farms require surprisingly modest CPU resources, but they need as much RAM as they can get -- and a fast pipe for access to storage and client workloads. These things the R815 can definitely deliver. By spreading virtual machines across such a large logical CPU count, you're essentially immune to overextending CPU resources, and with up to 512GB of RAM, you'd be hard-pressed to exhaust that either. The AMD Magny-Cours CPU doesn't extend to the 1TB of RAM that a Nehalem-EX server can deliver, but there aren't many cases where 1TB of RAM is a realistic expenditure in this server classification.
In short, the R815 can deliver as much virtualization horsepower in a single chassis as you might expect from three or four 1U servers. The four 1G copper Ethernet interfaces pose a potential bottleneck, but if you arm the R815 with optional 10G interfaces, there's no concern about network I/O to support all those VMs.
Twin SD cards and iDRAC6
While the R815 does have a maximum raw local disk capacity of 3TB in SAS or SATA drives, you don't need disk at all for some applications. The R815 contains a matched set of SD card slots inside the chassis. These slots can accommodate standard SD flash cards, and they are configured for redundancy. It's not a RAID mirror, but whatever's written to one SD card is written to the other. Thus, it's possible to install embedded hypervisors such as VMware ESXi straight to the SD cards and boot the server without any local hard drives whatsoever, reducing heat production, power consumption, and the problems associated with spinning disk.
I found the performance of the SD cards to be sluggish compared to hard disk, but that's a given. The fact is that once the server has booted an embedded hypervisor, there aren't many reads and writes from the SD cards, so there's no realistic performance degradation. The redundancy of the SD card slots also protects against the failure of one of the SD cards. You can even select which card to boot from.