The online dealer joins many NetApp shops in using VMware and NFS, although it has been running VMware longer than most. AutoTrader began using VMware in 2001 and has gone through every permutation of VMware storage from Fibre Channel, when that was all VMware would support, to iSCSI more recently. AutoTrader is also a longtime NetApp customer and is running some 20 FAS 3020, FAS 3040 and FAS 3050 filers, according to Jason Cornell, manager of the Windows systems group.
Most of the VMware storage is on a FAS 3040 and is used with iSCSI LUNs, but Cornell said the company is transitioning VMware to NFS mounts instead.
"Both iSCSI and NFS work fine, and the performance is about the same," he said. "It's a matter of supportability -- our admins understand supporting applications on NFS and have experience with that."
One potential drawback to the NFS move is that the Akorri Inc. monitoring tool that AutoTrader uses to troubleshoot virtual servers doesn't yet report on NFS. Cornell said that the Akorri tool has been invaluable for linking statistics on both the server and storage sides of the house, rather than focusing just on storage or just on ESX, as most tools do. But he hopes to be able to use it on NFS soon. "We're beta-testing NFS support with Akorri right now," Cornell said.
NFS gains momentum among VMware usersAn increasing number of VMware users have been coming forward in recent months to talk about using NFS. NFS mounts for VMware are still far from the norm, but experts said there are benefits to using it over block-access storage or even VMFS, VMware's virtual file system.
Although administering an Ethernet network is easier for most IT pros than managing a Fibre Channel fabric, iSCSI has its own complexities. Hardware iSCSI host bus adapters (HBAs) are required in environments looking to drive the best performance from iSCSI, and that introduces complexity and cost. And while the Ethernet protocol may be familiar to most IT staff, iSCSI may remain confusing. Meanwhile, "NFS says, here's an IP address, and here's an export," said Scott Lowe, national technical lead for virtualization with VAR ePlus inc.
Lowe, whose company resells VMware and NetApp, said another potential pitfall with iSCSI in VMware environments is that ESX requires its service console to interact with the iSCSI target. That sometimes requires ports to be added to servers or storage hardware.
Another advantage is that switching to NFS will allow AutoTrader to use NetApp's data protection features more efficiently, Cornell said. He noted that snapshots of iSCSI LUNs on his NetApp boxes require greater fractional reserve capacity overhead than file shares. NetApp says this best practice has been changed in version 7.1 of its Data OnTap operating system.
The NetApp factor
Burton Group analyst Chris Wolf agrees with Lowe that most VMware-NFS implementations have been in NetApp shops. That's because NetApp has built-in its own data protection features, such as snapshots and replication, and because NFS is "NetApp's bread and butter," as Lowe put it.
As a VMware partner, NetApp has also made those data protection features work more elegantly in its filers than standard Unix-based implementation of NFS. NetApp's filers can make hot backups of running virtual machines. Other systems will lock a virtual machine file if the virtual machine is running, requiring either a system pause or a copy of the virtual machine file to back up the data within it.
NetApp is also aggressively pushing NFS to VMware customers. "Sun could have a compelling case here, too, with Thumper," Lowe said. "They just haven't talked about it like NetApp has."