In direct attached storage (DAS) solutions, the storage media attach directly to a server, either internally or externally. Every server must have some directly attached storage devices because the NetWare sys: volume must reside (at least initially) on the server. Generally, external server storage refers to hardware storage arrays such as RAID and JOBD 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.
Novell NetWare server uses Novell eDirectory™ and Novell Storage Services to assign user access rights for directories and files, and to manage space restrictions.
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.