Help Yourself Centre What are Bad Sectors?
What are Bad Sectors?
Synopsis
A sector is a physical location on the hard drive that stores your data. A bad sector is a normal sector that has failed.Description
Bad Sectors can cause slow downs, resets, freezes and can also point to potential loss of data. There are possibly billions of sectors on a modern hard drive and just one or two bad sectors in the wrong place can be fatal for your data.
The first picture in the gallery below shows a hard drive platter. This is a disk that spins inside your hard drive. (A) shows the tracks moving outwards across the disk in concentric circles. (B) shows a 'Sector of Track' or a pizza slice. Where the track and the pizza slice intersect (C) is a sector (its a little more complicated than that, but for our usage, its enough!). Finally, you have a cluster of sectors (e.g. more than one) shown as D.
It is common to see a stripped appearence when we look at hard drive bad sectors - this is because the head that reads the disk moves across it like a record player. If the disk is spinning and the head is moving and then a shock happens, it will not take out a row of sectors but rather show a bad sector, then lots of good sectors, and then a bad sector and then good in a rough pattern. We can tell a lot by the pattern of bad sectors and this is taken into account when discussing keeping or replacing the drive.
The two other pictures show the platters (your data) and the mechanics. Note the gap between the head and the platter is less than the height of a finger print!
Gallery:
Symptoms
Freezing, Random Reboots, Blue Screens, Slow Computer
Causes
Dirt & Dust in drive, shaken or dropped, general wear & tear.
Prognosis
If there are less than 20 bad sectors and they are recovered, the drive should be useable (keep it backed up!). If more than 20 bad sectors, you'll likely need a new drive. This is a rule of thumb and the Techies will make a decision on a one by one basis.
Treatment
We use special software to try to recover the data, move it elsewhere and close the bad sector so it can no longer be used. If this doesn't work then depending on the state of the drive it could be a new drive and data transfer or a new drive, data recovery and windows reinstallation. There are many options and you'll need to talk it through. As a very general rule of thumb, if you can boot into Windows its probably repair rather than replace.
