OTG DiskXtender Merges NTFS with Storage Devices

Microsoft Corp.'s Windows NT Server lacks native disk controls that allow for file and directory aging or file pruning. These seemingly basic disk storage functions are key to a healthy file system and the proper clean up of a disk subsystem.

OTG Software Inc.'s DiskXtender is a tool that provides system-level disk services by merging Windows NT’s inherent NT File System (NTFS) functionality with secondary and tertiary storage devices, such as WORM drives, tape drives, and jukebox systems. DiskXtender does this by using SCSI driver extensions that mesh with Windows NT, so users of the server storage have no idea where the data come from, and the server is spared the accumulation of excess storage needs. The result is a form of hierarchical storage management system.

We tested the product on a Windows NT Server 4.0 with Service Pack 4 installed on an Intel Pentium II 400-MHz server with 320 MB of memory, 40 GB of fast SCSI storage, one HP 8100I CD recordable drive, and a Seagate DDS-2 SCSI-2 tape drive. The network had Cisco routing and switching equipment providing access to our four test servers running the agent software and a dozen test client systems.

The product installs in several steps, but starts with a test to ensure that NT Server is properly installed and running correctly. Make sure the SCSI devices you intend to extend are properly installed and running correctly. You’ll add devices later to the DX Server, so further extending the system is a no-brainer. The DX Server does not require much server memory, and it will use as much storage and media as you want to extend the overall system.

We installed the product on the DX Server, which controls the entire system. This can be any server on the network, but be aware that you’ll need administrative access to the server and physical control of the machine. We tested and verified one premise that OTG says should be observed: there should be a 1-1 ratio of SCSI host adapters to SCSI disk drives to attain and maintain optimal performance.

While this can be an expensive configuration, the DX Server environment typically serves well in excess of 100,000 files per server and over 1,000 active users. If this many disk I/O calls are made to one server, even Ultra2 SCSI disk subsystems could be pressed to their limits. This can be mitigated through the use of a three-channel SCSI RAID-5 adapter, but if you want to maximize disk channel performance put one or two drives on each channel that is not in a RAID configuration. We also tested the extensibility with our SCSI tape drives to move old data out to a semipermanent medium.

One installation aspect requires noting: In busy and large installations, the underlying network must be fully capable of supporting huge volumes of data transfers. This means switched Fast Ethernet 100 Mbps networks are the minimum that should be used for DiskXtender servers. If the servers are numerous and heavily used, then it would not be unrealistic to suggest the use of switched Gigabit Ethernet load-balancing equipment and Gigabit Ethernet server adapters.

After installing the system, you need to create rules that state when and how to move old and unused files. The movement of the old data is a function of several factors: what DX server is to receive the moved data, aging of the files, and media to store the data. We were given the DX Group of users when DiskXtender was installed. We made sure that all users that were needed were assigned to that group.

We defined a set of rules that moved one-week-old data that has not been accessed within seven calendar days. The files were moved to the CD recordable disc, then purged after another seven days. Further, we assigned the media to hold the moved files in stages, and then the schedule of the move itself. All of these operations were easily carried out using the administrator program. We had no problems working with any of DiskXtender’s functionality.

The DX Server environment is managed using RPC communications inherent to Windows NT Servers. In a large environment, expect a moderate amount of network traffic between the servers, hence the suggestion to have a solid performing network infrastructure. We configured the alerts of the servers to notify specific workstations or servers, which worked as expected. We enjoyed working with the various log files, system recording formats, and other reporting mechanisms. They provided information on how the media was working, projected failures in the server storage functions, and monitored other critical information.

It takes a little bit of work to get the overall system operational, but we found DiskXtender to have solid value. True, Windows 2000 will have some new file subsystem functions, but not everyone will migrate to Windows 2000 as soon as it is released. These enterprises can immediately benefit from DiskXtender. The only problems that we experienced were some SCSI driver operability problems with older devices, but those were quickly resolved.

DiskXtender 4.1
OTG Software Inc.
Bethesda, Md.
(301) 897.1400

Price: Priced according to the number of jukeboxes in the environment.

+ Excellent storage solution
+ Easy to manage policies
+ Easy to add new devices and adapt to changing storage needs

- Requires expensive hardware, servers, and network resources to manage large-scale environments
- May require a dedicated staff in the largest solutions, such as complete data centers

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