In direct attached storage (DAS) solutions, the storage media attach directly to a server, either internally or externally. Generally, external server storage refers to hardware storage arrays such as RAID arrays and JBOD arrays. These arrays connect through an external SCSI bus.
In a cross-platform environment, your DAS storage architecture can support native File Access Protocols (NFAPs). This enables data services to be accessed by clients using a variety of operating platforms. For an explanation of NFAPs, see Native File Access Protocols. The key difference between a DAS solution and a NAS solution is that the NAS server’s only job is to serve files to application servers or users; no applications run on the NAS server.
An OES server can use Novell eDirectory, NCP Server, and Novell Storage Services to assign user access rights for directories and files. NSS also allows you to manage space restrictions for volumes, directories, and users.
DAS solutions are typical of small offices and distributed network storage solutions. The DAS architecture creates islands of storage because the disks belong to the server and are not available for any overflow and support needs for other servers.
With DAS solutions, the server must be operational for its attached data to be accessible to users. If the server is offline or if the external storage device is offline, the server’s data is not available.
As your data grows, you can attach additional devices to the server up to the number of available slots on the SCSI bus. You also must consider the impact on I/O performance of adding additional devices on an already-busy SCSI bus. DAS works well for a few servers, each with a few hundred gigabytes of data.