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Top considerations when buying a NAS array

Purchasing a network attached storage (NAS) platform for your organization requires careful consideration. The top things to consider are how to manage it, how the information will be backed up and whether the

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platform can be scaled or enhanced.

NAS management

By far the simplest NAS decision for a company running a Windows and Active Directory environment is whether or not the storage will "join" the authentication environment. A NAS system with this capability allows users to access shares and files as if they were on a Windows based file server using the same logon and permission models that you and your users are familiar with. Always choose a platform that takes part in the Windows domain because it will then let you attach to the device and set up shares using Computer Manager and connecting to a different computer.

More NAS information:
SAN or NAS?

Determine whether implementing a storage area network or network-attached storage is right for your business.

Once the shares are remotely created the NTFS permissions can be assigned in the same way as if you were simply managing a normal Windows based server. Management of the NAS device itself is a question for your preference. Some offer a client-server type application to configure disk and RAID types; most offer a web based interface. There is no one method that is better, although the web interface for management can be preferable if some configuration needs to be done from outside the corporate network.

NAS performance

As with any storage calculations the question of IOPS is important. If you need 1 TB of visible storage you should not just purchase three 500 GB drives and make a RAID 5 array. Carefully balance the number of spindles (i.e. disks) with the capacity of the disks. Bigger is never better in situations such as these. The network connectivity to the system should be able to withstand any future increase in speed. If your main network is, for example, 100 Mb, then there is no reason your storage device cannot be 1 Gb or even 10 GbE in anticipation for any future expansion.

While most NAS appliances are used simply for file sharing purposes it is possible for them to provide HTTP, NFS (Oracle for example) or other protocols for application serving. Be careful though; Microsoft Exchange, SQL and many other enterprise applications do not support being connected to a NAS, only a SAN is supported. Be sure that the application vendor certifies that their data is supported on a particular NAS appliance.

NAS scalability

There's no point in choosing a system that is restricted in the size of disk drive it can contain. The platform you choose should be expandable so that more disks can be added -- either internally or through an additional disk chassis. Look for a system that allows you to add capacity without having to shut the NAS down.

There is very little point in putting the absolute maximum capacity into a NAS the day you buy it, for two reasons. The empty disks will just spin and spin, using up power and unnecessarily increasing your support costs. Also, storage utilization tends to increase, rapidly, to the level of the storage available. Having 5 TB of storage on day one can easily lead to using 5 TB far earlier than would be the case if you had added your storage by 1 TB at a time.

NAS backup

How to back up your data is the most important decision. Any NAS device allows you to connect over to the network and run a streaming backup but what exactly are you going to use to do that streaming backup and what kind of parallel network infrastructure are you going to use in order to conduct that backup. Streaming backups eliminate the ability to backup previous versions of a file stored on the NAS; probably the biggest reason you wanted to implement the networked storage in the first place. Choose a NAS that has a SCSI interface to allow the backups to be directly moved to tape. In addition, choose a backup application that will facilitate NDMP backups so that the VSS copies of previous file versions are sent to tape as well as current ones. There is no point in having a VSS aware backup solution if you are only able to secure the current version of a file.

Just because the NAS is not storing your business critical or a SAN mandated application data, does not mean that your unstructured data is any the less important to the users. Plan on ensuring that there are enough spindles in the disks to allow the NAS to perform better than the file servers it replaces, with greater storage than the replacement systems and backed up in a more flexible manner than legacy file servers allowed.

 About the author: Mark Arnold, MCSE+M, Microsoft MVP, is the principal consultant with LMA Consulting LLC, a Philadelphia, PA-based private messaging and storage consultancy. Mark assists customers in designs of SAN-based Exchange implementations. You can contact him at mark.arnold@msexchange.me.uk.


This was first published in April 2008

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