Development of NFS format

Networks are developed and shared. Therefore, sharing requires a storage space in the network. This also involves the NFS network file management system. Next we will look at the specific NFS format application in network storage. Most VMware-based vendors provide block-based fiber channel or iSCSI storage for their ESX servers, but some people have begun to propose Network File System NFS) it may be a more suitable choice. For example, when NFS designed a VMware-based dynamic service management host platform two years ago, IT commercial service provider T-Systems chose NFS.

Dr. Gregory Smith, Director of Dynamic Services, said, "We really think network NFS is the best choice." SAN has its advantages in throughput, but in terms of flexibility and management, NFS is much better ".

As an industrial standard shared file system, NFS volumes are easy to install and uninstall and support multiple clients. IT administrators also know about them. Smith further mentions the security advantages of NFS. Because the NFS format runs on Ethernet, T-Systems uses virtual LAN VLANs to isolate Virtual Machine VMS one by one. "The VM only sees their own things. You can place the file system on the LAN without considering the SAN, switch, and other things ."

On the contrary, the VMS in the SAN's VMFS cluster file system currently do not support separation of VM storage. It is difficult to use VMotion to migrate virtual machines through ESX hosts. Although ESX Server 3.5 that supports N_PORT ID virtualization will change this situation, NPIV is only supported by bare devices, but not by VMFS-VMware's proprietary file system.

T-Systems provides application services for approximately 70 servers and 80,000 end users. The system consists of NetApp network attached storage based on VMware's dynamic service platform. The company uses "a large number of [NetApp] OnTap Software Package functions" Smith said, including backing up through the remote image software Snappmirror and creating a 30-day archive through SnapVault, metroCluster allows you to create a dynamic Computer Cluster between Distributed Remote Data Centers. It supports failover and copies data from the master site to the remote site to ensure that the data is brand new.

Is performance at the cost controversial?

But what is its performance? "When you tell people that you plan to run VMware on NFS, people will think you are talking nonsense," said Scott Lowe, virtualization consultant for financial solutions and ePlus, an enterprise software company. This is because, from the perspective of swallowed up, the NFS format on Gigabit Ethernet cannot compete with 4G optical fiber. "If you only focus on throughput, the FC architecture beat NFS," Lowe said.

But Lowe and some of his partners pointed out an interesting paradox: the more VMS in an environment, the less obvious the FC throughput advantage. In fact, in a large environment, the actual performance of the NFS format may be better than that of the FC, Lowe said.

During the discussion of Multi-VM disk access, he said, "When you start to load VM in data storage, you are stuck in a SCSI congestion, as a result, all open hosts are blocked from accessing the LUNlogical unit number) "." The more hosts, the lower the throughput The FC can achieve. Therefore, you often cannot reach the theoretical throughput height ".

However, not everyone agrees with this idea. "It sounds a bit too FUD-Fear), Uncerntainty guess) and Doubt suspect)" said Greg Schulz, founder and analyst of StorageIO Group. "Of course, if you build a system for debate, you may encounter some problems. But if you follow the best operation method of the manufacturer, there should be no problem ". Schulz said that most fc san disk arrays recognized by VMware will publish the "Operation Guide", detailing the system speed and data volume, and the recommended maximum number of hosts, maximum number of VMS per port on the array.

In addition, the debate on disks does not exist in SAN, Schulz said. The same thing can happen on the NAS device, unless you are discussing the number of threads or login records rather than the initiator and target ends of SCSI.

James Price, president of Fairway Consulting Group, is very clear against the performance advantages of NAS. "NAS has a place," he said. "But I don't think you can find any well-trained storage engineer who will tell you that NAS can be used as the primary storage platform ".

First, the debate on disks mentioned by Lowe may be a defect in the previous version of ESX, but it is not that serious in the new version of VMFS integrated with virtualization architecture 3. Now, Price explains that no longer all hosts in the same cluster share a log through disk access. Now it is equivalent that each host has its own dedicated log, eliminates communication congestion.

Second, Price is worried about adding a layer of Protocol due to a third-party file system NFS), leading to system complexity. "The real threat to NAS is block-level input/output I/O for other file systems," he said. "It's not visible from ESX ". In addition, you cannot perform many operations when using NFS to store data, such as out-of-band operations such as backup, cluster, SAN import, and bare metal ".

However, ePlus Lowe said more users are taking the NFS route, including "a large number of users starting to migrate data from their top-level FC storage to NFS," he said. Not to mention performance issues. Part of the charm of the NFS format is derived from the features of the vendor's products, such as NetApp. "For them, backing up all the data is a huge challenge and there is no way to solve it. They have seen VMware's unified backup, but are not very satisfied. "" Lowe said. Now they have decided to use NetApp's NFS volume, through which, "they can get data from the customers who have built it, and backup is now much easier ."