5. Rotation speed
The hard disk is often the slowest element of a PC. It’s a lot slower than a processor. It’s especially because it’s mechanic. A disk is composed of a plate in constant rotation and a read/write head who moves on the plate to read and write the data. So we can improve the data transfer rate improving the rotation speed of the plate. But keep in mind that doesn’t really improve the access time because for the transfer time, the principal problem is the shift of the head.
We have to distinguish here the 2″1/2 and 3″1/2 format because the speeds are not the same.
5.1. Hard disk for laptop : 2″1/2 format
Here are the different speeds for a 2″1/2 hard disk :
- 4200 rpm : It’s the old version of the hard disk. That’s not a good idea to buy one now.
- 5400 rpm : It’s the standard speed for laptop hard disk.
- 7200 rpm : More and more hard disks are sell with this speed
A hard disk with 5400 rpm is still comfortable, but it’s really a good investment to buy a 7200rpm hard disk.
5.2. Hard disks for desktop computer : 3″1/2 format
Here are the different speeds for a 3″1/2 hard disk :
- 5400 Tours/min : It’s the old version of the hard disk, not used anymore.
- 7200 Tours/min : It’s the standard speed for desktop hard disk.
- 10’000 Tours/min : This is only SATA and SCSI hard disk. The capacity of this kind of disk is often limited.
- 15’000 Tours/min : This is only SCSI hard disk. You’ll find only this disks in servers, very expensive.
For the hard disks for store your data, I recommend to use 7200rpm hard disk. But for the main disk, to store operating system and your programs, i recommend a 10’000 rpm with little capacity (36 or 72 Go). That will improve the start of your system and of your programs. It’s really comfortable to work with.
6. Memory cache
The actual hard disk have also a cache memory. This memory is used to store the most used data bits that can be reused. When this data are requested, they come directly from the memory cache so without mechanical access, this is faster. We have several memory cache sizes :
- 64Mo (very rare)
It’s a bad idea to buy disk with less than 8Mo of memory cache. If you can, i recommend you to buy hard disk with at least 16Mo. 32Mo or 64Mo will be better but more expensive.