SAN Gets The Ink, But NAS Does The Work.
To other IT professionals, there may be some confusion about the difference between SAN and NAS. To others, there may be questions about what a NAS device really is. To some, these things don't really matter--as long as there's a device that meets a particular need, they don't really care what you call it.
In some ways, the idea of a Network Attached Storage device is a natural extension, doing for storage what a print server may have done for printing a few years ago or what a CD-ROM server may have started doing for a network a year or two ago. The idea, essentially, is that a NAS is a product that is easy to install and configure--plug in a network cable, identify the device on the network, and start working.
In essence, as long as the device is designed for storage (and not just data retrieval, as networked CD-ROM servers do), then the device is performing Network Attached Storage. To be clear, the lines can be considered somewhat blurry--would a hard drive installed into a workstation, but accessible over a network connection, be considered a NAS?
For the purposes of this article, a NAS is a device that is connected to the network by means of a network cable, in most cases, an Ethernet cable. The NAS will have one or more hard drives and may also contain such other storage devices as a tape drive or DVD-RAM drive. A pure data playback device, like a networked CD-ROM or DVD-ROM server wouldn't be considered NAS for the purposes of this article, although it can be argued that these devices allow retrieval of stored data, if not actually performing the storage tasks.
Evolution Of The NAS
Just a few years ago, the idea of Network Attached Storage was somewhat exotic. If storage was to be added to a network, this usually meant additional drives being added to a server or a JBOD box added to a server. The drives were seen as additions to existing hardware, not as an independent storage device.
Meridian Data, with its Snap Server, may have been the first with a true NAS device. This device performed the basic functions of a NAS device--providing storage that could be easily added to a network merely by connecting an Ethernet cable from the network to the drive, turning on power, and running a configuration utility. Last year, Quantum Corporation acquired Meridian. Creative Design Solutions (CDS) similarly developed hardware and software for network-attached devices. Last year, Maxtor acquired CDS.
So, in short order, two of the leading hard drive manufacturers had acquired new technologies that could leverage their drives into new markets. This year, new NAS systems, including some NAS devices that include RAID capabilities and that are designed for rack mounting are bringing the NAS products up from the small desktop and small network onto Enterprise racks.
At the low end, both Quantum's Snap Server and Maxtor's Max Attach products are available in one and two drive units. Quantum's entry level, single drive Snap Server 1000 provides 10GB storage, while the MaxAttach A0201 offers 20GB. Quantum's Snap Server 2000 is a two drive unit, offering 20GB of storage, and is priced comparably to the 20GB MaxAttach unit.
Stepping higher up the scale, both vendors offer 40GB Network Attached Storage devices. The multi-drive units can be configured for various flavors of RAID, if the user desires the extra performance or security that RAID implementations can offer. Both vendors use IDE drives in their NAS devices.
Maxtor has indicated that it will be offering a version of the MaxAttach product that is designed for rack mounting. Details were not available at press time.
At the end of February, Quantum announced a rack mount version of its Snap Server that will offer up to 120GB of storage. The unit will be RAID-enabled, allowing the user to choose which RAID level to implement. The unit will have a suggested list price of $2,999.
A HP Offering
While the Quantum and Maxtor offerings, at this instant, are designed as relatively low priced devices for adding storage to a network (the Snap 1000 with a single 10GB drive lists for $499) and might be considered to be more for the small office than for an enterprise, Hewlett-Packard has been offering a NAS device with the earmarks of a more enterprise-ready system--the HP SureStore HD Server 4000. The Server 4000 is a sturdy HP blue box with six drive bays. The base unit includes three 9GB SCSI drives, although the system can support up to six 18GB hard drives. A front panel enables the administrator to assign a MAC address and configure the device for the network.
The SureStore HD Server 4000 is available with a DAT 40 (DDS4) tape drive and can, thus, be used to back up data from the drives on the 4000. In addition, an external SCSI port allows connection of external SCSI tape drives.
The unit supports RAID 5 with hot spare capability and ships with redundant power supplies as standard features. A 300MHz 32bit RISC processor and 128MB of RAM support management of the installed components. The 4000 can be managed over a network using a standard browser. Additionally, the SureStore HD Server 4000 is also available in a rack mount configuration. IBM has recently announced a product it defines as a NAS.
Roll Your Own (Sort Of)
Axis Communications offers an enclosure with a networking interface that enables the design of a network-attached device using vendor supplied drives. Pioneer and other companies used the Axis design to develop such devices as DVD-ROM and CD-ROM servers. Conceivably, using the Axis architecture, a developer can create a network addressable device that includes multiple hard drives.
As noted in the beginning of this article, some users don't care how a NAS is defined--as long as it meets their requirements. The low end devices, with prices below $1,000, often fall below levels that require approvals by management before purchasing.
These relatively portable devices have been implemented for a wide range of applications. For example, the devices have been used to provide an easy way to add storage without the hassle of opening a server and installing a drive. With easy connection to a company's network, the downtime required to install a new drive can be eliminated.
Additionally, some NAS devices have been used for data portability. Data that must be moved from one physical location can be copied onto a NAS device and physically transported between locations.
Some computer support technicians use NAS devices as temporary drives that can hold a user's data while the user's hard drive is being replaced or repaired. Additionally, NAS devices have been used to distribute large amounts of data to multiple offices--the data is recorded onto a bank of NAS devices that are shipped from a central location out to the field. In some ways, this can almost be thought of as rotating data backup, with old NAS devices returned to the central location when NAS boxes with newer data arrive. The "old" boxes can be erased and new data recorded onto them for distribution when the next update cycle occurs.
As drive capacities continue their inexorable climb, the size (but not necessarily price) of storage capacity on NAS devices will also continue to increase. Next year's base unit may well sport 20GB or 40GB or more, minimum capacity, at about the same price as that for today's 10GB or 20GB units.
Although it may seem that the major performance limitation is the Ethernet connection between the NAS box and the network, with 10Mbit/sec or lOOMbit/sec maximum data transfer rate, according to Quantum, Ethernet may not be a significant limiting factor. Quantum's upcoming 120GB rackmount NAS device is said to provide better performance than NT file servers with similar capacity. Whatever you choose to call a NAS device, it is clear that they'll be around for some time, meeting the varied requirements of a wide range of users, from the end user/SOHO environment all the way up to the Enterprise.
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|Publication:||Computer Technology Review|
|Date:||Feb 1, 2000|
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