Original: http://10495845.blog.51cto.com/10485845/1721926
The storage world can be overwhelming, and choosing which storage platform to use (let alone which vendor to use) can be a real challenge. Let's start by looking at a few major storage technologies.
1. Direct Attached Storage (DAS)
This can be taken literally: connecting directly to the server, which was the earliest way disks and hosts were connected to each other. For small installations, this method may still be the best option. DAS is cheap, easy to install and support, but DAS is not scalable, and the basic installation lacks the data redundancy of the following two types of products. However, since all you're buying is a bunch of disks, don't expect too much.
DAS performance can be improved with hardware RAID SCSI cards for enhanced redundancy, or Fibre Channel connected disks for higher scalability. However, if you really do, you might as well consider one of the following solutions: NAS or SAN.
2. Network Attached Storage (NAS)
Network Attached Storage (NAS) is a storage system accessed through an IP network and uses the NFS or CIFS protocol (NFS is the Unix protocol, CIFS is the Windows protocol). Both protocols can actually operate on data at the file level, so when you change the data, you are changing the entire file. This is helpful for users who edit spreadsheets that change infrequently (since the spreadsheets reside in the local PC's memory), but is not suitable for large-scale databases, which may have many files in the hundreds of megabytes . For these large-scale demands, there is an important role for the storage infrastructure: the SAN.
3. Storage Area Network (SAN)
A storage area network allows many storage components and hosts to be connected to each other using an infrastructure called Fibre Channel. Fibre Channel includes multiple switches and fiber optic cables and is implemented like an IP network. However, SAN configurations tend to be tighter in structure, designed with redundancy in mind and minimizing the number of switch connections between hosts and disks. Unfortunately, SANs are the most expensive infrastructure to implement and therefore the most expensive to support. As for the advantages, SANs are extremely scalable. It is also very flexible if implemented properly.
So how do you choose which technology to implement? First, analyze your needs. Are you supplying the storage system to end users using PC workstations or to servers? If the former, then a NAS may be the most cost-effective solution. Today, the latest NAS servers have features designed specifically for the operating system to meet the needs of workstation-based users, including storage capacity management, fast restarts to minimize server downtime, and low-speed backup and recovery for immediate backup and recovery. Cost replication and data snapshots.
If you plan to provide storage for servers, then a DAS or SAN might be fine. Both infrastructures can provide disks that appear to the host as if they were SCSI-attached local disks, thus providing block-level access to files. As a rule of thumb, you should ask yourself the following questions: Do I need more than 10-20GB of storage? Will storage requirements increase? Can a simple hardware RAID or host-based RAID solution be used?
If the answer is yes, then DAS is more suitable. If no, then SAN should be selected.
It's worth mentioning here that hybrid technologies, such as iSCSI and SAN blades, are blurring the line between NAS and SAN. iSCSI can provide the SCSI protocol across IP networks, using dedicated hardware adapters, or using software drivers. At first glance, this solution appears to be less expensive than implementing a dedicated SAN. However, most administrators choose to implement a dedicated iSCSI network for performance reasons. SAN blades allow NAS devices to provide disks for storage area networks (SANs). This approach definitely has potential in situations where reducing the cost of the disk subsystem is critical, such as in development environments.
No matter what your disk needs are, the options for providing storage systems continue to grow and become more complex. What we can be sure of is that storage platform decisions won't get any easier in the next few years.