More Data on Partitions
In the feedback from the ConfiguringYour Partitions article there were three common questions, whichare addressed here.
Isn't the Outside Track Faster?
There has been discussion of speed advantages on disks with fixedlength sectors. Such disks have more sectors on the outermost tracks (or cylinders) than they do in the inner tracks,so data can be read faster from the outer tracks. On a 3.5" diameter disk, the innermost track is about 3"long and the outermost about 11" long. So you can read almost 4 times as much data from one revolution ofthe outermost track. Sounds impressive, but what does it really mean?
If the disk spins at 6000 RPM, it takes ten milliseconds (ms) to makeone revolution. This means that, regardless of any other factors, after you have moved the read/write head to asector, it's going to take an average of 5 ms for the disk to rotate and bring the data to the head (this is called"latency".) Sometimes you'll luck out and the data will be right there, sometimes it will take almosta full revolution; on average, it will be half a revolution, or 5 ms. Only then will the actual reading or writingof the data begin.
A sector typically holds 512 bytes. The number of sectors per trackvaries widely: a 1GB disk may have 500 sectors per track, a 2.5GB disk may have 1500. For a simple example, let'sassume 1000 sectors per track average. That means we'll have 400 sectors (200KB) on the inner track, and 1600 (800KB)on the outer track.
If you are going to read a large amount of data, more than will fiton a track (more than 200KB in this example), then having the data on the outer tracks will save time -- but notmore than 5 or 10 ms. The vast majority of disk I/Os are a lot less than 200KB, so most sites will never benefitfrom this speed difference. In addition, you may have some bad sectors, which will have been replaced with sparesectors. The Logical Cluster Number (LCN) will be in sequence with the other clusters in the file you are reading,but the physical location could be anywhere on the disk.
The bottom line is, while some sites, especially those that regularlyread hundreds of KB at a time, may benefit from the speed difference between inner and outer tracks, for most sites,the disk latency and head travel time will completely overshadow any speed gains; it's just too small a percentageof the total access time to be worth spending your time on.
FAT or NTFS for the Boot/System Partition
FAT format has been recommended for the boot partition, so that inthe event of a catastrophic failure, you can recover by booting from a bootable DOS floppy and then repair WindowsNT. The disadvantage, which many have protested, is that you lose all of the security benefits of NTFS. An alternative,which has worked for us, is to have a second boot partition on another disk drive and install WindowsNT into that. This secondary Windows NT can be a minimal installation to save disk space. Should your primary bootpartition become corrupted, you can boot to the secondary and then repair the primary. Thus you can use NTFS onall partitions, and still have a relatively easy recovery path. See the article Multiple Boot Systems for more data.
Specialized Partitions - What if You Run Out of Space?
There have been several comments on the specialized partition schemein the article Configuring Your Partitions , the objection being that you would run out of free space sooner. At some sites, this is true. Whilewe believe that our plan is best for most sites, no single plan for partitioning is going to be suitable for allsites. We know of one case where a single 4.5GB partition is the most efficient plan.
If you are going to break up a disk into smaller partitions, you needto plan ahead and leave room for expansion, especially on the system partition. However, virtually every partitionis eventually going to fill up, and a new or larger partition will be needed. We favor creating a completely newpartition and copying the data over, but not deleting the original files until you are sure the copies are good.Once you are sure you have lost no data, then you can delete the original files and use the old partition for someother purpose.
Additional Point
One person stated that we were wrong about not having to frequentlyback up a partition that contained only system files, because 1) registry and profile data are frequently updatedand 2) many applications put files on the system partition which then are updated often. We researched this andfound that he was right. At some sites (e.g., a personal machine at home), this doesn't matter, but most siteswould be well advised to keep the system partition, and probably the application partition, backed up frequently.The larger the site, the more important this will be.
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Executive Software Europe
