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Storage Toolkit

Where do you put all your data?

Tags:
NAS,
SAN,
DAS

Scott Lowe Tech Republic

Published: 16 Dec 2004 10:50 GMT

Direct-attached storage
Just about anyone who's ever touched a server is familiar with DAS. DAS is the storage that fits right into the server or that hangs off the server. For example, storage connected to a server's external SCSI channel is also considered direct-attached storage.

DAS has enjoyed a long history and is still the storage of choice in many situations. With the fastest transfer rates between the disk system and the server, DAS is ideal in situations where fast disk access is demanded, although some new SAN equipment is starting to give DAS a run for its money in this department. Further, most applications have no trouble at all working in a DAS environment, so you don't usually need to worry about application issues and can focus on other areas that might cause problems instead.

Not all is rosy with DAS, however. First and foremost, IT managers must constantly contend with "space issues" which attend to answer to common questions:

How much storage do I need to provision for a new server?
What do I do if my provisioning wasn't quite right and I need to add space?

Some options on the market help to alleviate the storage burden related to these questions, but either way, you still need to make best-guess estimates regarding storage and then expand that storage as unanticipated needs surface.

Second, you still have to manage most DAS on a server-by-server basis meaning that you need a mechanism in place to monitor server disk usage per physical unit. Not many IT managers relish the thought of running out of disk space in the middle of the day!

DAS is ideal in a number of situations:

When fast access to storage is required, but the newest SAN technology prices remain out of reach or are not necessary.
For very cost-conscious customers, DAS will remain the least expensive storage mechanism for a long time. Of course, this is only in terms of hard physical media costs. When a full comparison with other technologies is completed that takes into consideration administrative overhead and storage efficiencies, you might find that DAS is not at the top of the chart anymore.
For very small environments that just don't need anything more.

Direct-attached Storage | Network-attached Storage
Storage-Area Networks