Analyze the advantages and disadvantages of network storage categories

For most large and medium-sized businesses, high-performance requirements can be achieved with Fibre Channel SAN systems; relatively inexpensive iSCSI SANs and network-attached storage are often better suited for enterprises that lack experience in data storage.

"Frankly, these are good, in reality, consider the performance, availability, or some other characteristic is not the decisive factor in selecting iSCSI, Fiber or the NAS." Stephen Foskett said. He works for an independent enterprise storage consulting firm in Ohio, saying that when VMware supports these systems, "I often tell them to choose the most suitable solution, because at the end, they will find that no one is better than the other. good. "

" this is a product based on a comparison between the various storage vendors, but this is not the basis for the final decision. "Gartner research vice president Robert Passmore said. He pointed out that a NAS vendor may have more useful features than a SAN vendor, or vice versa.

some companies choose different types of storage with virtual servers, for example, tend to frequently change the data or development environment to deploy NAS; configuring high-performance systems for its production SAN, EMC senior technical marketing manager, said DaveHenry representation . Each network storage may have its advantages in a particular virtual server environment, and its pros and cons are also consistent with non-virtual server environments.

IT departments are listed below in considering which network their storage in virtual server environments using networked storage class can refer to some key advantages and disadvantages.

Network Storage Type:

1, NAS

2, FCSAN

3, iSCSI SAN

NAS

storage category: advantages

1) ease of installation, operation and maintenance and management. Organizations that lack storage administrators can bypass many storage professional protocols and terminology. They can use the familiar network interface cards (NICs), cabling, and Ethernet switches to choose a cheap precursor Ethernet network for easier service.

"You don't have to understand LUNs, don't worry about head contention," said Marc Staimer, general manager of Dragon Slayer Consulting. "Installing VMware or Xen Server will be extremely easy, just in a Hyper-V environment. under a little complicated, but still easier than iSCSI or fiber. "

" when creating a volume for the virtual hosts by VMware virtual host file system (virtual Machine fileSystem, referred to VMFS), the volume to a file The form is stored and appears as a file on the NFS file system on the NAS device," Gartner's Passmore said. "So storage vendors like NetApp and EMC can perform independent snapshots, replication, and recovery of virtual hosts. and other operations to provide only a ESX server volume. "

2) with respect to the block stored in the VMFS more simple file system extensions. "Usually, VMFS is not very flexible as a file system," Foskett analysts said. "Assuming you created a 100GB VMFS on VMware ESX, you need 110GB. The only way is to add another volume as an additional extension. to this VMFS, rather than VMFS migrate offline, create a migration to go back a new volume. "

" through NFS, you are free to expand capacity as needed, "he continued," you can so you do not have to worry about storage capacity issues. "

VMFS can now support up to 2TB, and the file system can also be combined.

3) block-based storage system that I /O queue mode, NAS flexibility to handle concurrent access to the same time as compared to the same hard disk. "This means a big difference in a virtual server environment," Foskett said. "You may inadvertently let 10, 50 or 100 I/O requests access different files on the same disk at the same time, and this may cause problem "

network storage category: inferior

1) the potential loss of performance under high traffic load. "If you don't use NAS, performance will be much better," said Bob Laliberte, senior analyst at ESG. He believes that transaction-oriented databases may not be suitable for NAS, especially in virtual environments.

2) support for advanced features Vmware slow. Vmware often supports some new features in a SAN environment, at least six months before the support in the NAS. For example, VMWare is the first to support Site Recovery Manager (SRM) in fiber and iSCSI SANs, "because these are more commonly used in large data centers," said Venue Aravamudan, senior product marketing director at VMware.

"Sometimes we focus on those areas most likely to quickly apply to these products or the API to develop," Aravamudan said, "It's only because of our own limited resources, does not mean to say which is better networked storage solutions. many users choose to use the NAS, which is currently the fastest-growing areas. "

but Vmware is still a lack of support NAS environment characteristics, such as its vStorage API for multiple links. In NFSv3, VMWare currently only supports one data path per NFS, EMC's Henry pointed out. Dragon Slayer's Staimer said he is looking forward to supporting Parallel NFS (pNFS) in the next generation of VMware products to solve this problem.

"undoubtedly has a very strong current SAN multipathing support," NetApp virtualization and cloud computing Vaughn Stewart, director mentioned in the message, "NAS must rely on network redundancy technologies to meet and flexible link aggregation path "

3) NAS has been the problem:. CPU load and file system scalability issues. "The biggest problem with most file-based storage is how much you can scale," said Staimer of Dragon Slayer Consulting. He pointed out that the scalability of each vendor is different. "The number of objects that each NAS storage system can handle still has certain limitations. When this threshold is reached, basically the database is full and no more data can be processed. you can not read any data, but there is no advance warning system. "

Foskett pointed out NAS is a centralized high-level protocol, decoding requires a lot of translation work, consume large amounts of processing power. In a virtual server environment, a physical server hosts a large number of virtual hosts. Compared to a server running a single application, a traditional server architecture that may only use 5% or 10% of processor resources has consumed more of its processor resources. He says.