free drive space

ok was reading a topic about defragging a hard drive where someone was advising that for best pc performance you need about 15% of your hard drive free, and it got me thinking. years ago yes i would say 10-15% was a good estimate, where memory was smaller,say 512k, along with hard drives about 50GB, max file size say 4GB for a video, so there's at least 5GB+ for file swapping etc, and read/write speeds were slower. but does that really still hold true for todays pc's where say memory is 3GB, hard drive is 500GB and max file size is still 4GB, and read/write speeds are faster but now you'd be keeping 50GB free(wasted) when you only really need say 10GB for file swapping etc. without any drastic loss in performance or has the actual size space in Gb's got nothing to do with the performance issues and it's all to do with how the drive space is allocated and used that's the problem for drastic performance losses that are noticeable like browsers web pages being slow to open. ok i understand how drives are faster when read from the outer edge of the platter and slower on the inner(or is it the other way round ) but for actual daily use even the slowest read/write speeds of todays drives shouldn't(in my opinion) be noticeable when just browsing the web or doing normal daily stuff while keeping 2% of a 500GB(10GB) free for any file swapping. gaming then yes ok where max drive speeds can make a big difference in gaming performance, i can understand keeping a drive relatively empty, but i'm not talking about hard core gamers here but the average person who's pc's have probably worked the hardest playing flash games on facebook.. even tho i use 1TB drives i still get new ones when they get to about 20% free.. and i have 4 now.. but at 15% for each drive that's 600GB wasted. so thought i'd just ask the experts for their opinions.. wow that's the longest post i've written since i don't know when..

The more free space is available, the easier it is to defragment. I assume the general theory of fragmentation is known; files get deleted, this leaves gaps, and other files are put into these gaps. If the file doesn't fit into the gap it gets fragmented between one or more gaps, and this decreases read/write performance as the head has to jump around. The reason we need to still hold that 10-15% is because files are a lot larger these days - texture packs for games can be in one large contiguous file, people download blu-ray rips of movies that go into the 10s of gigabytes etc… we use a lot more space, but the files are also a lot larger in size. To shuffle a 15GB file around to make it contiguous when there's only 10GB of free space is possible, but takes a lot longer than if there is a bunch of free space that it can be put into, other files shuffled around, and then it put where it needs to go. Also, the average person who plays flash games on Facebook isn't likely to fill their whole drive to begin with.

oh i don't know over the years you'd be surprised what fills up an average users pc. pictures/music from kids phones usually. 15% of a 1 TB drive is 150GB now you tell me what file is any where near 150GB in size, i'm not really talking about defragging(yes i do have a basic understanding on how it works and why linux doesn't need it as much) anyway but on the actual noticeable performance drop we used to see with older pc's when their drives got to full, and i mean really slow boots and slower surfing etc, that's why a %age figure first started getting used for best performance i believe. i know seek times and stuff increase with the more data a drive holds but with todays drives is 15% really necessary to keep free before someone will come looking for help because their pc is running slooow, like they used to? i don't believe it is… but then again i'm usually wrong.. and it's nice to hear everyone's thoughts/experiences on the matter.

Terry, without having a definitive answer, I've often considered the same. If we used your line of reasoning, wouldn't it be possible to for instance run a defrag as long as there remained as much FREE Space as the size of the largest file on the disk, or maybe FREE Space twice as large as the largest file just to be generous? But even that seems tight, since in other uses, for instance photo, video, or sound editing, the application software would need a space as large as the file it is working on, in order to keep backup for 'clipboard' type go-back reversal when the user didn't like the result. And some editing applications are able to go-back through several changed iterations of the same file. Experientially, it seems to me that the 15% rule remains a sensible recommendation. I do appreciate that there could be a point of waste when considering 15% of very large disks. Yet disk function (again experientially) seems to decrease at about 25% FREE Space remaining.

yes i agree with you doug drive performance takes a bigger hit the more data on it, but i'd like to see any links people might have that show by what percentage that drop is and if it effects daily usage of a pc to be noticeable enough that they need help with a slow pc. must admit never heard that performance started to drop off at the 25% free space remaining figure tho, thought it would be much higher. personally yes i think a 25GB figure would be enough free drive space on todays drives but like you and everyone else here i still follow the 10/15% rule. in theory by my thinking with linux, i guess i could fill my drives to 1% or less without it becoming unbearable slow. because we usually have a separate partition for swapping, just as long as i made it twice the size of my 6GB memory, but i'm not about to test it tho.. i also wonder if it is the hard drive or just the way windows allocates and uses it's file swapping that there needs to be a %age figure and not a set in stone figure of X GBs.