Hard Drive Partitioning

Scott L. Barber first posted this to Quadlist. It is reprinted with his permission.

"How come my folders/apps inflated in size when I moved them from the old drive to the new one? The size of files has jumped by more than 25% across the board. Did I do something wrong in simply dragging the entire contents from the old drive the new one?"

The HFS format has an ability to hold a maximum of 65,536 files and allocation blocks. Lets say that you had a 1 GB drive with that many files - each file could take up a 16k. Since we must deal with extremes, the minimum file size then is 16k. So, no matter how small a file is, it will always take up at least 16k on the disk. This was the infamous 2 GB limit, where files could reach a minimum allocation maximum of 32k - hence 2 GB maxed this. HFS was patched with System 7.5 to support 4 GB partitions and to eliminate certain file type sizes - which is why empty folders take up 0k. But even so, files minimums are 64k, and with 7.6, 64 GB partitions were allowed (1 MB allocations per file).

Apple replaced this just recently with Mac OS 8.1 when they created HFS Plus, a variable block allocation system that is decided on format. Block sizes are reported as 2k, but are as small as 512 bytes in certain formats and at certain sizes. Unfortunately, 68k machines cannot support this new format properly, and no one really has decent utilities to deal with it (Norton chokes - Tech Tool Pro 2.0 is the only current package that deals with them right). Only 68040 machines can read them, and it's a processing hog to work with them, so I don't recommend HFS+ with a 68040.

"Am I guessing correctly that Speed Disk (NU version 2.0) can't handle a 2 GB drive? It keeps telling me to allocate more memory to the app, but I brought it up to 10,000 and still can't get it to run."

Yep . . . it's lost - it can only handle 2 GB drives. I'd have partitioned it out into a few partitions anyway . . . one for downloads, one for work apps, one for games - keeps one bad file from wiping out everything - just one partition . . . this is important if you download a lot from the internet, and if you play a lot of poorly written games that could toast a drive. By partitioning you're protecting worthless data from damaging a drive, and protecting worthwhile data from being wiped out. I even have a 50 MB cache partition just for Netscape - so that the cache folder doesn't blow up my boot volume one day.

To give you an idea of what I mean . . .

I have a 9 GB drive. Here's how I have it partitioned out.

• Boot Volume - System folder and system related items only - 750 MB (I need the size to print large files - spools can get huge
• CD-R Master - I copy all CD's to this partition right before cutting, to avoid any optimization problems. 750 MB
• Internet Download - 1 GB - all downloads are to this drive. Nothing is ever opened here - just downloaded.
• Pentium - 1 GB - I keep my Virtual PC folders and applications here, so they don't accidentally become contaminated by any other files on the machine - if one drive file gets damaged, I must start all over again.
• Scratch Disk - 3+ GB. I unarchive all downloads to this disk and try them out before deciding to trash or keep them. I also use this for temporary or project work in graphics or web pages. This gives me a playing field without compromising the integrity of any other important partition - if an application crashes and blows up the partition, I haven't lost a thing. This is also my primary scratch disk in Photoshop - Internet Download is my secondary.
• Work drive - this is where all my serious applications and games are stored. If I think it's a safe game - one I'll play constantly, or a serious installed application, they reside here - most of the time this disk isn't written too - only run from - that's the safest way to have a drive - especially with thousands of dollars of high end software on it (Quark, the entire Adobe line, etc.) This drive is 2 GB, but only 1 GB full right now. Plenty of room to breathe.
• Cache - finally, the cache disk - 50 MB - I moved all cache folders for me and my wife and other guests over to this drive, and set the preferences there, too . . . if the cache ever blows up - it only blows up a 50 MB partition that I can always reformat. Also, I no longer have to clean it regularly - I simply wait for disaster to strike before I toast it.

Now, I'm not trying to brag about the size of my drive - I'm trying to teach - if you have a 1 GB drive, I always format 250 MB out and carve up the rest into two or three pieces - 100 MB for download, 500 for work, and 150 for scratch space. The original 250 is for Boot Volume, so that the system folder toasting doesn't take out all your applications and force a reinstall. Hope this makes sense to everyone, and teaches a little about storage security.

Addendum

I wanted to add, with a quick explanation, just how I partitioned my drive, and in what specific order, and why.

1. Boot Volume
2. CD-R Master
3. Internet Download
4. Pentium
5. Work Drive
6. Cache (see A RAM Disk Alternative before creating a Cache partition)

Boot Volume was formatted first and carved out in the very beginning in setup. I took some time determining the exact size so that this partition couldn't accidentally be relocated in another spot in the physical drive location, because the first part of a drive is always on the outside of the hard drive platen. On the outside, data is accessed faster, as more blocks are located on outer tracks than inner tracks, so more data can be read per rotation (rotation on a hard drive is fixed). When you read that a maximum drive speed is 14 MB/sec, it's always the measurement of reading the outer track. The innermost track may be 1/12th of this speed, simply because of the circumference (which is why AV drives spin faster, so that the inner tracks are more useful).

I want the Boot Volume, and subsequently any data from the system folder needed, to be available as fast as possible compared to any other data on any partition of the drive. This will make the system more stable and more responsive, and nearly guarantees that there will not be timing failures due to slow drive access to the system folder.

Next, the CD-R Master volume, my partition for cutting to my CD-R drive, is my next fastest priority. Since I must maintain a consistent high rate of data transfer, I wanted to make sure that the area being read on the drive wouldn't provide my CD-R drive any excuses to have a buffer underrun . . . again, this is a SCSI intensive process, and relies heavily on SCSI timing - I want to give a CD-R write all the possible advantages.

Internet Download needs to be fast, so that there aren't write problems with multiple downloads. If I'm downloading 30 simultaneous files, I need to know that the constant reads and writes to multiple files from Netscape's buffer won't collide on the SCSI bus, or overflow the buffer and start backing up in the SCSI chain, this is one of the most common reasons I see Netscape lock up during a file download because Netscape doesn't have a large internal application buffer to handle overruns or holds from the media chain. Usually, this causes hiccups in the TCP/IP stack and throws up a broken pipe to force a re-download of the file.

Pentium could go anywhere - I don't use it enough to care very much. It just happened to be the variable in the deck. It has higher priority than Scratch disk only because large sections of the partition are taken up by the VPC drive file, which I'd like a decent drive response out of when reading or writing inside the program.

Scratch disk was the extra space available - it doesn't really count either, except I do desire that it has a higher priority than the next two partitions, simply because Photoshop accesses it so very often as it's scratch file - I want a quick response if I can get it.

Work Drive is the last on the chain for several reasons. When Applications are launched, delays are always in the initialization of memory and application items, and are very rarely inhibited by the drive speed. I want all my applications loaded on the slowest part of the drive, so that I'm not tempted to save documents or large pictures to the drive by accident, and being on the end of the drive, used almost always as a read only partition, is damn near completely safe from all of the other partition problems. If bad writes occur to the Boot Volume, the chances of them bleeding over to the Work Drive are nil, unless they damage all of the other partitions as well. Drive failure rarely occurs on the inside tracks of a hard drive, meaning this is the safest place for all my expensive applications that would take me days to reinstall.

Scott L. Barber <serker@serker.com>