Network attached storage (NAS) appliances
typically contain their own internal storage resources. Storage
capacity is expanded by simply adding more
disks to the appliance. Obviously, this only
allows users to scale up to the capacity limit of the appliance.
NAS
gateways overcome these inherent limitations
of scale and flexibility by utilizing externally connected
storage. In some cases, the external storage may be a standalone
disk array. It's also common for a NAS gateway to share storage
through a
storage area network (SAN), allowing users
to consolidate their NAS data on SAN storage and realize the
benefits of high performance and redundancy. Major NAS vendors
offer tools that can migrate data from NAS appliances to their
NAS gateway products, which can also support all NAS protocols
and many operating systems environments. Now that you've
reviewed the
essential issues involved in any NAS
product, this Buying Guide focuses on specific
considerations for NAS gateway products. You'll also find a
series of specifications to help make on-the-spot product
comparisons between vendors, like EMC Corp., Hewlett-Packard
Corp. (HP), IBM, Network Appliance Inc. (NetApp) and more.
@29998 Evaluate interoperability between the gateway and
storage. Not all gateways work with every storage subsystem.
This is particularly important if you're connecting to SAN storage.
For example, the Bobcat Series NAS gateway from ONStor Inc.
supports disk arrays from disk array vendors, including Hitachi
Data Systems Inc. (HDS), EMC, IBM and HP. It's important to start
by checking the vendor's compatibility matrix, but in-house testing
is also strongly encouraged to verify compatibility.
Even NAS gateways have capacity limits. Even though a NAS
gateway is intended to use external storage resources, there is
still a finite limit that the gateway can address. For example,
Hitachi NAS Blades can be clustered to support up to 512 terabytes
(TB) per cluster. This isn't a problem for most organizations
today, but potential storage limits should always be considered
when planning a new gateway deployment.
Remember that some features move to the storage. By
moving storage outside of the NAS gateway, remember that some
features will be dependent on the storage subsystem(s) being used.
For example, an NS700 series NAS gateway from EMC does not provide
RAID or disk scrubbing, but the gateway
supports Symmetrix and Clariion storage, which does include RAID
and disk-scrubbing features. Changing storage platforms may add
new features or remove existing features, and this can easily
change the way that data is managed through the gateway. Storage
administrators must consider how changes to the storage
infrastructure will influence NAS capabilities.
Consider the connectivity. With external storage,
connectivity is essential to ensure adequate performance across the
user base. In most cases, you can expect an array of Ethernet and
Fibre Channel (FC) ports. As an example, the
StorageTek 5320 NAS gateway from Sun Microsystems Inc. provides
four standard 10/100/1000 Base-T Ethernet ports and two
dual-port 2 Gbps FC HBAs, with up to two optional dual-port
10/100/1000 Base-T ports. The IBM N5000 gateway is similar with
four full-duplex 10/100/1000 Base-T Ethernet ports and four 2
Gbps FC ports onboard. Connectivity not only supports expansion,
but connections can also be used to enable highly available
features, such as failover for reliability or port aggregation
for improved performance.
Evaluate standard features. Pay close attention to the
variety of features that ship standard with the NAS gateway,
including clustering, mirroring, replication, reporting, volume
management and so on. For example, the IBM N5000 gateway ships with
a suite of software features, including FlexVol, snapshot, fast
boot, email alerts, NIS, DNS, SNMP, FilerView, NDMP, LDAP and
AutoSupport. In addition, a gateway should support the network
protocols of any applications that will be using NAS storage, so
consider the support for network protocols, such as CIFS, FTP, HTTP
and others.
Evaluate optional features and licenses. Don't just
assume that every function and protocol is supported as a standard
feature. There are often many features available as options that
can inflate both the initial and ongoing costs of a NAS gateway.
Examples of optional software features might include mirroring,
restoration, cloning and management tools. Even network protocols,
like NFS, CIFS, HTTP and FCP, are considered optional on the IBM
N5000 gateway, along with their FlexClone, MultiStore, Clustered
Failover (CFO), SnapMirror, SnapRestore, SnapVault, SyncMirror,
SnapValidator, SnapDrive for Windows, SnapDrive for UNIX, Single
Mailbox Recovery for Exchange, SnapManager for Exchange,
SnapManager for SQL, SnapManager for Oracle, Operations Manager,
SnapLock Enterprise and LockVault Enterprise software.Options and
licenses can dramatically increase the gateway's TCO.
Consider the impact of virtualization. Virtual server
capability allows NAS gateways to appear on the LAN as a complete
NAS device with a unique identity, IP address and security
authentication. This allows NAS gateways to be relocated,
maintained and scaled without disruptions and data migrations.
Storage virtualization allows capacity to be added and configured
as necessary, while eliminating wasted (unused) storage space.
Gateways, like the ONStor Bobcat, tout support for both types of
virtualization.
The NAS gateway product specifications page in this chapter
covers the following products:
- EMC Corp.; EMC Corp.; Celerra NS40G/NS80G NAS
gateway
- EMC Corp.; EMC Corp.; Celerra NSX NAS gateway
- Hewlett-Packard Co.; HP StorageWorks EFS Clustered
Gateway
- IBM; N5000 Gateway
- IBM; N7000 Gateway
- Neopath Networks Inc.; File Director 220 gateway
- Neopath Networks Inc.; File Director 7200 gateway
- Network Appliance Inc.; V-Series NAS gateway
- ONStor, Inc.; ONStor, Inc.; Bobcat Series NAS
Gateway
- Sun Microsystems Inc.; StorageTek 5320 NAS Gateway
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