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Saturday, 22 November 2014

Customer Problem 1: The Slow Laptop

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A while back I had a blog on Google+ linked to my freelance IT business and I started recording some case studies. I think I only did a few in the end but I thought I'd share them anyway.

The Problem:

I have just finished working on a laptop that was coming up with a lot of errors in Windows (e.g. explorer.exe crashing) and general very poor performance (e.g. Applications taking an eternity to load along with Windows itself). At first, it appeared that it was a performance issue such as a lack of memory, or that there might have been malware causing issues but resolving these made no difference. The weirdest thing about it was the inconsistency - sometimes it worked, sometimes it didn't. The first part of fixing a problem is seeing a pattern or, even better, knowing the exact circumstances under which a problem makes itself apparent (replicating the problem).

The Investigation:

The machine was relatively old (socket 775 Core 2 Duo) and had been upgraded to Windows 7 from Windows XP, yet it still had 1GB of RAM. No brainer - an upgrade to 2Gb (£15) was necessary, but didn't appear to make any difference at first. It was then I put my ear to the hard disk and heard the tell-tell sound of bad sectors. This is easy when you're working on a laptop - not so much with a desktop computer.

Bad sectors don't actually make any noise. Sectors are the physical, measurable areas on a hard disk where files are stored. Small files may only occupy a single sector but, more commonly, a file will be spread across a group of sectors. If any of these sectors become damaged, the hard drive will repeatedly attempt to access the data until it either succeeds or gives up (a bit like when a scratched CD skips). This can manifest as a repetitive 'clicking' sound, usually in a recognisable pattern. While it may appear like something taking forever to load it's actually because of the pauses during the retries.

Bad sectors usually happen when a hard drive receives some kind of physical shock or jolt when it's in the process of reading data from the disk platters. Data is read from the disk by a 'head' that floats micrometers above the magnetic disk (or platter). If the head touches the disk, physical damage can occur and this results in bad sectors. This usually occurs when a laptop is dropped or knocked. While most laptops have built-in protection to prevent this kind of damage, it can't completely quash the forces of physics. Fortunately, most hard disk manufacturers provide free software that can scan your disk and identify such damage. But, if there are too many, the program will say the disk is defective. Of course it will - they want you to buy a replacement, so the tolerance level is set very low.

This problem can occur with any laptop or computer using mechanical magnetic media such as a hard disk drive. SSDs are immune to this specific problem, but they have their own issues.

The Solution:

More fortunate still, there is free software that will 'remap' the bad sectors. It will mark the damaged parts of the disk as unusable, and attempt to relocate the data on that sector. Sometimes it works, sometimes it doesn't, and there is always a risk of data loss. If you have too many bad sectors, replacing the hard disk is usually a good idea, but if there are only a few, you might be lucky enough not to lose any data at all and continue using the drive. I use a program called ViVARD, which is on the Ultimate Boot CD (UBCD), a free collection of tools and utilities that boots from either a CD or a USB stick.

In this instance, the physical damage was not widespread and the remapping worked. I left it running all night and the client rebooted the computer in the morning. Windows immediately began running better - no crashes, no pauses, no lag, all aided by the RAM upgrade (Windows XP struggles with anything less than 2Gb).

The Lesson:

Don't move your laptop any distance when it's powered on. If you need to relocated, put it to sleep or shut it down. Most laptops go to sleep when you close the lid but make sure you check this is the case before you move it!

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