Storage architecture choices: SAN, NAS or DAS? - February 15, 2008
Storage area networks (SANs), which were once available only to large enterprises that could afford to pay steep premiums for the best storage, are increasingly moving downstream. "SANs combine the benefits of shared storage with those of direct-attached storage (DAS), and newer technologies make them affordable even for small businesses, says Storage Vetern and President of Sencilo Solutions of Orlando Florida. This article will explore why storage area network (SAN) devices may be right for you.
Storage acronyms: SAN, NAS and DAS
The three main ways of connecting storage to servers are SANs, network-attached storage (NAS) and DAS. With DAS, which is the most basic form of the three, the drive connects directly to the server and is often even in the same enclosure. Because DAS is simple to install and requires no large, IT-level planning, it's still what many small and medium-sized businesses (SMBs) rely on, said McCarthy.
SANs and NAS both separate data storage from servers, allowing servers to share those resources. NAS devices have their own file system, so they work best as file servers, that because their OS is designed to handle file data very quickly. SANs give block-level access and appear to computers as normal drives, so they work better for applications such as databases. Companies start needing databases once they reach about 50 users, which is why even small businesses are starting to look into storage area networks, McCarthy said. SANs handle block data well, where as file data is better off on a NAS systems. Most modern SAN are designed to handle both SAN and NAS unlike older EMC or Open Source units from Equal Logic or Lefthand Networks that require a file server. Look for units from NetApp, HDS or MDI in which you can consolidate both file and block data, and retire older File Servers.
Benefits of SANs
Why storage area networks? Depending on how many servers your client has, a SAN can offer significant advantages over a DAS array for each server. Consolidating storage devices will save your clients money by allowing them to buy capacity according to what the entire company needs, as opposed to having each server work with its own disk array, much of which may go unused. Provisioning tools can let your client dynamically allocate space -- instead of giving a server 100 GB in anticipation of growth in a few years, an IT manager can give it 25 to 50 GBs and increase that as needed, McCarthy said, this is offer known as Thin Provisioning.
Because SANs can consist of several physically separate drives or arrays, they also offer replication and disaster recovery features. For instance, you can set up two SANs with automatic, real-time replication. If the primary SAN goes down for any reason, the system will automatically fail over to the second.
SANs also complement server virtualization. One of the features of some virtualization software is the ability to move images between physical servers on the fly, without downtime. This requires the two servers to share the same storage device -- both so they can access the same data and to serve as a medium for the virtual machine (VM) image.
Cost of SANs
A SAN can works on a Fibre Channel (FC) network. The wires may be either fiber-optic or copper, but since even the copper FC wires supporting 2 to 4 Gb/sec transfers are different than Ethernet cables, all FC-connected SANs require a separate, dedicated network.
Fibre Channel equipment is expensive; the wires, which are often optical, can cost $100 to $200 each, and each device's FC adapter will cost another $400 to $1,000, said Henry Baltazar, storage analyst for The 451 Group in San Francisco. This extra infrastructure makes up the bulk of the cost for SANs that use FC, which is why storage area networks have traditionally been reserved for larger companies while smaller companies are going with iSCSI SANs.
But iSCSI, a variant on the SCSI interface that runs over IP, can eliminate those costs by connecting your SAN devices over your existing LAN. Your client will still need to make a few adjustments, such as configuring a virtual LAN (VLAN) for the SAN drives to ensure that they get all the bandwidth they need; your role should include helping the client with this implementation work. An entry-level iSCSI-attached SAN can cost as little as $10,000 including implementation services, McCarthy said. "I expect iSCSI will soon ship more units then FC-based unit, since iSCSI is far easy to run then a complex Fibre Channel ones".
About Us
Sencilo Solutions is a Florida-based integrator specializing in storage and security solutions. Sencilo delivers a comprehensive portfolio of products from best-of-breed hardware and software from multiple manufacturers including VMware, EMC, Juniper Networks, Hitachi, Symantec, Barracuda Networks, and HP. Its technical expertise is known throughout the storage and security industry. Clients include leading corporations, major financial institutions, top universities, government facilities, as well as small to medium size businesses. Sencilo's professional services include consulting, integration, project management, installation, maintenance and knowledge transfer.
Sencilo has offices throughout Florida including: Jacksonville, Daytona Beach, Miami, Tampa, St. Petersburg, Orlando, Hialeah, St. Augustine, Gainesville, Ocala, Palm Coast, Clearwater, Kissimmee, Lakeland, Maitland and Cape Canaveral
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