Does short-stroking really work on HDDs? How should it be done?

Rafael Mestdag,

Imagine that a hard drive is like a record player in which the data is on a magnetically encoded spinning record. There is an arm that pivots on a center across the disk to find the correct piece of information and the head retrieves the data to use it.

This happens very quickly as the arm /retrieval head has a short distance to move, but it does have to change direction and make many movements per second- that. the clicking / crackling sound you hear when the HD is working.

So there is a time lag- the access time in ms- for this to work. Imagine then if you can put the data in a more condensed form and better order by putting the files all into one continuous piece- defragmentation- - and the access time is less-t he information is retrieved- or written faster.

Then there is a further improvement if the space containing the information is reduced so that and taking all the spaces between the files out - consolidation. The consolidation can be improved if the total space allowed for the data is a minimal amount larger than the data volume. Say fro example, the HD i a total of 1TB but only contains 100MB. it possible for the data to be spread over the entire 1TB csapce and this means the arm has to travel all over the disk to read or write. If the 1TB HD gowver has a 120MB partition, the arm movements- the shifts in position are much shorter for access- "short- shifting". The access time of SSD's is so fast it really is not useful

So, to have short-shifting, place data or programs in a partition that is 10-15% larger than the data- it needs some room to operate efficienctly and defrag and consolidate and this will make a mechanical drive faster. The access time of SSD's is so fast it really is not useful and even degragging is a wasted wear on the memory.

The other aspect of it is to arrange the partitions so the most used information is in the partition on the outside portion of the disk where the data is in effect travelling faster.

I've used short-shifting over the years and almost always have three or four logical drives- partitions- on the mechanical drive- one for archived file, one for media, one for software, and one for system image to restore the system quickly. And, it's been quite effective, but mech'l drives are much faster and more and more, the active files under use can be kept on an SSD partition as the price per GB has dropped. The day is not too far off that mech'l drives will be rare on PC's and I think these will also be increasingly PCIe.
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[A little computer history. My father was involved with computers since the early 1960's - we had a modem the size of a desk at home in 1971- you put a phone in a cradle and dialed the system. There was no monitor, the computer (IBM 360) typed everything out and when my father would sign in, the system would type, "Good morning Bill. What would you like to do today?" - which I thought was just magic and amazingly futuristic.

He was very pleased that the company had bought a new device called a "Hard Disk" - data then was stored on tapes that had to be shunted back and forth, but a HD could retrieve the data very quickly. The platters were not 2.5" or 3.5" in diameter, but were 20" across and there I think 6 or 8 of them in a stack. The astounding thing was the total storage was 5MB- that's Mega not Giga- and the price- almost $50,000! I bought a 540MB HD in 1994 for $570- that's about $1.1 per MB so a 1TB drive at that rate would have cost $1,100,000.]

The good old days of computers are now!


Cheers,

BambiBoom

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