Limitations of Remote Storage

HSM is not a new concept; it has been available on legacy systems for many years. The ideal server-based HSM system should satisfy several wishes before it can be classified as a true HSM system, the dream of every network administrator. The most important of these wishes, according to our vision of the ideal HSM system, are as follows:

♦ The HSM system must be a network service, able to coexist with any distributed file system.

♦ The HSM system must support a recall override or recall prevention option.

♦ The HSM system must coexist with standard backup and restore procedures and technology.

♦ The HSM system must support all forms of removable or remote media, on any server on the network (running on Windows 2000 or 2003, of course).

The HSM system made possible by the Remote Storage service has several limitations. First, the Remote Storage service is currently available only to the server on which it is installed. This means that you have to install the service and compliant hardware on every server you wish to place under HSM or Managed Volume status. This is clearly a lot more expensive than disk quota management.

Many companies spend a lot of money investing in a good tape library system for the benefit of all servers. To replicate the investment on each server on which you need HSM would wipe out the cost benefit; sticking in new hard disks would be cheaper. A good tape system starts at about $4,000 and runs to more than $20,000 for a good DLT or DAT library system (see Chapter 20 for details on DLT and DAT systems). However, you can pick up a single 70GB hard disk for a fraction of that cost. Double this for the media duplication feature discussed earlier. Incidentally, the cheaper tape backup hardware discussed in Chapter 20, like QIC, is not supported by Remote Storage.

Second, the current version of Remote Storage does not support the capability to override recalls. This means that all software that attempts to read a file will inadvertently recall it from the library or tape drive system, unless the software has been built with Remote Storage support (such as the Backup utility that ships with Windows Server 2003).

Granted, software will have to become Remote Storage-aware, but this will be a problem for many applications, such as third-party backup software, antivirus software, indexing software, document management systems, and so on. It will take a while before all software is endowed with the ability to work on managed volumes, but it would be nice to set times or other parameters that would cause the recall not to fire. As mentioned earlier, the recall limit is a step in this direction, but it would have been better to program the service to recognize who is reading a file marker before recalling the file. The operating system knows which service or user account is accessing a file.

HSM might save you time and money managing a hard disk, but you could lose that benefit with the added diligence required in the backing up and restoring of data. Once the data has been relocated, Remote Storage leaves a file marker or placeholder on the media. (The marker is represented by the same icon owned by the file, but superimposed with a small clock.) So, what does your backup program back up . . . a placeholder, a token of what was once valuable data? And what do you restore in the event of a hard disk crash . . . the version in the backup or the version on the Remote Storage folder?

In addition, Remote Storage brings with it the possibility of losing relocated data. Placeholders and caching data can get deleted and corrupted, possibly even becoming the target of e-terror. The media used to store the data is not impervious to damage or loss. The additional brain strain is not what many Windows server administrators would welcome. The ideal HSM system should be fully integrated with a backup program.

Note Some third-party HSM products have catered to many of the aforementioned limitations, including Veritas (Symantec), which contributed much of the backup, remote, and removable storage applications in Windows 2000 and Windows Server 2003.

Despite these reservations, we are referring to the first version of what is clearly a valuable addition to the operating system. As the previous example of the newsroom demonstrated, it can be put to good use, and it works very well. If you wish to investigate the Remote Storage service further, go to Microsoft's Web site and search there using the keyword "RSS."

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