Network attached storage (NAS) appliances
are frequently touted for bringing convenience and simplicity to
network storage. Appliances include their own dedicated disks
for storage and
RAID, and most NAS appliances can be
upgraded with more or larger
disks for additional storage space. If even
more storage is required, another NAS appliance can be added to
the network. NAS devices typically run their own proprietary
operating system (OS) and are managed and configured using
integrated software utilities that run across any standard Web
browser. This allows storage administrators to check NAS status,
diagnose issues and make changes to the NAS configuration from
any workstation on the
local area network (LAN).
However, NAS appliances do pose some disadvantages. First, they
are file-based and not appropriate for every application -- some
applications simply need the SAN . Second, their LAN connectivity
can present a potential
bottleneck for network users trying to
access storage. Consequently, the choice of NAS appliance
requires careful evaluation. Now that you've reviewed the
essential issues involved in any NAS
product, this guide focuses on specific considerations for
dedicated NAS appliance products. You'll also find a series of
specifications to help make on-the-spot product comparisons
between vendors, like Agami Systems, Dell Inc., EMC Corp., IBM,
ONStor Inc., Sun Microsystems Inc. and more.
@29474 Watch for additional or hidden fees. Not all of
the features listed for a NAS appliance are standard. Some features
and functionality may carry additional costs for upgrades or
software licensing, adversely impacting the TCO. When comparing
product costs, be sure to compare costs with all necessary features
enabled, and factor in any upgrade or licensing costs involved in
future scalability.
Consider the capacity and connectivity. Select a NAS
appliance that will offer adequate storage capacity in the near
term and suitable expandability into the future. An undersized NAS
appliance will typically force users to purchase additional
appliances -- resulting in additional capital expense and
management overhead. Also, ensure that the NAS appliance provides
suitable
Fibre Channel (FC) or Ethernet connectivity
with enough ports to support the expected storage traffic. For
example, the Snap Server 18000 from Adaptec Inc. incorporates
two
Gigabit Ethernet (GigE) ports for
connectivity. By comparison, IBM's N7000 Modular Disk Storage
System supports up to 12 GigE ports or up to 16 2 Gbit FC
ports.
Consider any necessary infrastructure changes. Heavy data
transfers can easily overwhelm a LAN. Understand the implications
of traffic changes on the intended network segment, and plan to
accommodate upgrades or infrastructure changes that might be needed
to achieve best performance. For example, adding a standalone NAS
to a lightly used network segment may require a move from 100 Mbps
Ethernet to GigE or the utilization of multiple GigE ports in
busier environments. Organizations that need the performance of SAN
storage may opt for a NAS gateway, rather than a NAS appliance. The
NAS vendor might be able to help with network planning.
Consider the platform implications. The choice of
platform can have a profound impact on the scalability, performance
and manageability of NAS devices. Industry experts note that
appliances based on Microsoft Windows (e.g., Windows Storage Server
2003 Release 2) are typically simpler to implement and manage,
while proprietary appliances, such as EMC Corp.'s Celerra or
Network Appliance Inc.'s (NetApp) products, often support greater
scalability and performance. Proprietary appliances sometimes
integrate more functionality, such as snapshots, which can add
significant value to an enterprise.
Evaluate the support for RAID. Most NAS appliances offer
data protection through internal
RAID, so consider the RAID levels that will
be most beneficial for your appliance. Support for RAID 0
(striping), RAID 1 (mirroring) and RAID 5 (parity) is common.
RAID 6 (double parity) is appearing in appliances that rely on
high-density SATA disk -- though support for RAID 6 is not yet
universal. For example, Adaptec Inc.'s Snap Server 18000 and
EMC's Celerra support RAID 1 and RAID 5, but the StoreVault S500
includes RAID-DP; a variation of RAID 6 double parity. Remember
that your choice of RAID will impact the total usable storage
capacity of the appliance. For example, RAID 1 mirrors disk
contents, effectively cutting the total storage capacity in
half. RAID 5 requires a disk in every RAID group dedicated to
parity data. RAID 6 demands two additional disks in every RAID
group for parity data.
Consider other forms of NAS data protection. Beyond local
RAID features, a NAS appliance may offer support for
snapshots,
replication and
backup. Be sure to identify the suitable
snapshot or replication targets; a NAS appliance that can
replicate to any heterogeneous storage platform may be
preferable to an appliance that can only replicate to a
duplicate heterogeneous appliance. Industry experts emphasize
the importance of backup and recovery compatibility -- the NAS
appliance should be compatible with your existing
backup/recovery software and should not impose any special
requirements on backup or recovery processes. As an example, the
Adaptec Snap Server 18000 integrates BakBone Software Inc.'s
NetVault software and offers backup agent support for Veritas,
CA Inc., NetWorker and
NDMP tools.
Consider internal support for tiered storage. Some NAS
appliances can provide internal support for multiple disk types,
and this can be a notable feature for organizations that practice
tiered storage; for example, the Pantera
2200 Clustered NAS from ONStor supports serial attached SCSI
(SAS) disks for performance and SATA disks for high-volume
storage. This allows NAS appliances to be included within
storage tiers. In many cases, both drive types can be supported
simultaneously for internal tiering.
The NAS appliance product specifications page in this chapter
covers the following products:
- Adaptec Inc.; Snap Server 520
- Adaptec Inc.; Snap Server 550
- Agami Systems; Agami Information Server (AIS) 3000 & 6000
series
- BlueArc Corp.; Titan 2200 NAS
- Buffalo Technology; TeraStation Pro NAS 2.0 TB
- Dell Inc.; Dell PowerVault NX1950
- Dell Inc.; Dell Storage Server PE840
- Dell Inc.; Dell Storage Server PE2900
- Dell Inc.; Dell Storage Server PE2950
- EMC Corp.; EMC Celerra IP Storage; NS20
- EMC Corp.; EMC Celerra IP Storage; NS40
- EMC Corp.; EMC Celerra IP Storage; NS80
- Hewlett-Packard Co.; HP ProLiant DL380 G5 Storage
Server
- Hitachi Data Systems Inc.; Hitachi NAS Blade for
TagmaStore
- IBM; N7000 Modular Disk Storage System
- Iomega Corp.; StorCenter Pro NAS 250d 750 GB
- Iomega Corp.; StorCenter Pro NAS 250d 1.5T
- Intel Corp.; Intel Storage System SSR212MC2
- Network Appliance Inc.; StoreVault S500 appliance
- Network Appliance Inc.; FAS270c
- ONStor Inc.; Pantera Series Clustered NAS
- Sun Microsystems Inc.; StorageTek 5220 NAS Appliance
- Sun Microsystems Inc.; StorageTek 5320 NAS Appliance
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