The other day I was reading a computer magazine and noticed in an advertisement there were 2 types of Western Digital HDD. One type had (2MB Cache), while the other more expensive type had (8MB Cache).

Besides the obvious, (6 more MB of Cache ) what effect will this have in terms of general speed, data transfer, access times etc.
What I'm really trying to say is: Would the extra 6MB improve the creation of images from CD to HDD? What exactly does the extra 6MB of Cache do?

I'm very interested because I will be needing a new HDD sometime soon. Anyone with info, comments, suggestions please help. Thanks in advance.

Cache effects should not be measured in data transfer and access times, which measure the performance of the hard drive, and not the effect of data that may or may not be in the cache.

The advantage of a large cache is just as it appears, it allows more data to be stored. If the data that is requested is already in the cache, the hard drive need not be accessed and an instantaneous RAM transfer from the cache at the full speed of the IDE protocol in use. The larger the cache, the more likely that requested data may be in it.

If the WD Mode 5 Ultra ATA (UDMA 100) is in use, data from the cache will theoretically be transferred at 100 MB/sec, which is much faster than the hard drive transfer speed of the single drive. Western Digital's specs for this drive show a buffer (cache) to disk max speed of 736 Mb/sec, or 92 MB/sec.

As well as that, the 8MB cache WD hard-drives have a 3 year warranty from WD.

The 2MB versions only have a 1 year warranty.

The 8MB cache do result in increased performance, in any environment, especially database and raid(0) applications.

Not only the cache is increased but its firmware is especially tweaked for normal desktop usage. I'm sure you can find a review at Storagereview.

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I'm seeing Maxtor drives now with 8MB too.
I bought one of the WD a couple months ago, and have been so impressed with the improved performance, that i bought a second one for my second drive. There are some rebates on them lately. I posted in the bargin basement about that.
I notice the performance boost mainly is delivering large database and similar data. I think virus scanning is faster too. I don't see any difference in things like drive copying or imaging though.
I don't see any difference in CD burning either, although I regularly run 2 instances of Nero and burn different image files to each instance (CDRW drive) off the same HD, at 40x. It may be my imagination, but I think the 8MB HD is a little better at keeping up.
They are also whisper quiet, I can't hear them over the case fans.

I recently bought a 80Gb WD drive, and I regret it.... besides the fact that I choose the 2MB version instead of the 8MB version (stupid me), I already have bad sectors on the drive

Anyhow, I don't think you'll go wrong with buying the 8MB version of the drive. The performance increases a lot, if I may believe recent reviews... and that's sure worth a little bit more money...!

To avoid misunderstandings:

When using a proper OS (which included proper caching), the drives increased cache alone would not gain much speed. But as already said, the bigger cache is not the only improvement of WD JB drives

That would be because the caching algorithmns in the 8MB drive would allow it to read ahead and buffer more of the 1st image, then when it moves to the positon of the second image, buffer more again.

Lets assume that the drive reads 1/2 it's cache for each image.

A 2MB chace HD would read 1MB of the first image, then 1 MB of the second image.

So it would need to move the read heads (650 * 2) / 1MB = 1300 times to read the data for the 2 images.

In comparison the 8MB cache HD realises that programs are requesting the same files repeatedly, and so will read ahead by 4MB.
so (650*2) / 4 = 325.

So 1/4 of the number of seeks. The seek time we all know is the most time consuming of any HD operation, so reducing the seeks by 75% will speed up the HD significantly.

I will point out that this isn't entirely accurate because their are other factors, but I'm sure everyone gets where this is going.

But the fact that you can reduce the amount of RAM being used makes up for it. And again, each HD is different, and the OS's caching algorithms are very general, even though you can choose "desktop, server, etc" cahcing options. The caching optimisation will always be better if done by the manufacturer as they know the hardware limitations of their gear.