I've been looking into getting a new RAID-1 solution, and hence will have some shiny new HDD's to play with.
In the past I've always partitioned my drives - ALWAYS apart from the organisational benefits, i was led to believe it was marginally more efficient (when viewing the root of a partition it only needed to examine that region of the disk, as opposed to examining the whole disk to display the root), and that fragmentation could be kept a little better if you heavily use one partition and only lightly use another..
I want to make the "right" choice for my new drives: So, is there really any reason beyond organisational (C - programs, D - Music, E - Videos, F - Games etc... etc..) to partition a large drive?
Having data in separate partitions, (apart from the OS partition) can still be a lifesaver. I've seen many situations where the active partition on a HDD might fail, and data can still be recovered from logical partitions on the disk, without resorting to an expensive data recovery operation, when all software solutions fail.
Having separate partitions is also very useful when using imaging software to back up data. Although many programs allow images to be burned directly to CD/DVD disks, I still think the better solution is to first place the image on a separate HDD partition, and then burn the image to optical media. This gives you more than one method to restore a partition if damaged or infected by a virus, and also gives you a better chance of the image data being valid. Nothing hurts more than needing to restore a partition and then discovering the image data is corrupt.
Even with NTFS, fragmentation is still an issue, and so, having data that is less frequently accessed in separate partitions is a good idea. This way, since the OS partition normally needs defragmented more often than any other, it encourages users to defragment the smaller partition more frequently; speeding up launch application speed, and saving wear and tear on the HDD, which lengthens the life of the disk.
And finally, being able to move data from partition to partition can be an extremely useful option to have available, if something goes wrong with a partition table, or the system needs to be reorganized for one reason or another - (case in point; adding extra disk drives, and wanting to transfer data without backing it up first to optical media.) I did this recently, myself, as I added 240GB to a system, and the previously created partitions on the original disks could be resized and used for other purposes. Having to move around a quarter of a million files was time-consuming, but far easier with a simple cut-and-paste than backing up all the data first (which was already copied and secured across the network, for those who flinch at the idea of losing the data due to a glitch or a power loss! LOL!)
Because of these reasons, I think that intelligently partitioning off a hard drive is still the best solution, even in these days of affordable RAID mirrors, network backups, and cheaper, large HDDs. Data is data ... and no one likes to lose it.
I rarely think about partitioning in terms of simple organization. Folders and subdirectories are sufficient for keeping a system nice and neat. Saving data (and being able to restore it without error), and keeping a hard drive at low fragmentation levels ... those are more important priorities.
When backing up data, having varied methods available is certainly not redundant. You'll pat yourself on the back at a later date if that "Games" partition becomes inaccessible, and instead of having to recreate the partition and reinstall all the applications, a recent image is readily available on another hard drive, (and if those games are on the OS partition, you'll also be looking at reinstalling the entire OS ... needlessly, from my point of view.) Optical media is definitely a good idea for partition restoration, but replacing that partition is a heck of a lot easier if there is also a verified, valid copy on a separate area of a disk.
Some may claim that having one partition is sufficient if backups are made regularly, especially with NTFS in place, but in rebuttal ... Time can sometimes be an issue (unless you live the life of Riley), and it's faster to restore a partition from a disk than from optical media. And you can't image a partition and copy the image to it at the same time. I consider my images on DVD to be the backup for my primary backup, which is kept on the last logical drive of the least frequently accessed HDD in the system.
Well, that's my long-winded opinion, anyway. <GRIN>
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