Defragmentation and NetWare
One of the truisms of NetWare is that the traditional storage system has no need of defragmentation.
In a desktop operating system (such as DOS or Windows), file storage blocks become scattered around a disk drive, meaning that multiple passes of the read head are necessary to retrieve a file. Disk defragmenter utilities organize the data blocks so that fewer passes are needed to read the file.
NetWare uses a queue-based data block retrieval mechanism called "elevator seeking" that optimizes reads based on the path the read head will travel. A fragmented file, then, should be as quickly retrieved as one that isn't.
I did some tests on this theory a number of years ago (back around 1992), and found it to be part fact, part myth.
I took a 1G-byte disk drive that typically ran 95% full and included a number of files that were frequently modified or replaced. That's a good formula for fragmenting your storage. One weekend when I had the server all to myself, I did a series of reads and writes and timed them. I then backed up all the files on the server, deleted and reinitialized the drive, then restored all of the data. Repeating the same tests, I found that read times had been reduced (I didn't keep the data, so I don't have the actual times).
The difference was relatively small (on the order of 7-10% faster), but it was enough to demonstrate to me that fragmentation was a problem with NetWare drives -- though not as big a problem as with Windows drives.
Unfortunately, when I performed those tests there were no defragmenting utilities available for NetWare. Backing up, deleting, then restoring an entire drive is both too time-consuming and too fraught with danger (suppose the backup tape breaks?) to make it worthwhile.
That's about to change. John Hanley, the man who created Ghost (the disk cloning software) and Ghost for NetWare, is about to launch a defragmenter for NetWare. This is a tool to watch for. Just as soon as it’s available, we'll be telling you more.
» posted by ITworld staff
Network World
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