You may have noticed that over the past few years the sizes of hard-disk drives has grown tremendously. If I look on Amazon.com today, i can see 1.5 Terabyte hard-drives for around $150. Wow! That is pretty cheap.
So, you may ask yourself, do I still need to compress imagery? I have got these massive hard-disks, maybe I don't have to worry about it. But there is something you need to be aware of....
Disk speed is pretty much the same as it was 10 or more years ago
Overlooked by many, particularly hard-ware vendors and IT departments that like spending (your) money, is that whilst there has been massive growth in the capacity of hard disks drive, they are pretty much the same SPEED that they were years ago. Speed increases have been a lot slower in coming about than the increase in disk size.
There have been some "trivial" movements with "SCSI" and SATA drives. 5400 or 7200 revolutions per minute compared to 10,000 or 15,000. Not much of a comparison when you compare it to 80GB to 1.5 Terabytes.
The constant rate of disk speed is no better emphasized that with "seek time". "Seek time" is the time it takes to "find" your information on your disk. This has stayed "static" for the most part in the last 10 or more years.
The relative slowness in hard-disk speed means that, among other things it will still take the around the same amount of time to "read" your images today as it did 10 years ago.
This means that the larger the "data" on the disc, the slower it will be to "read", regardless of having a "big hard-disk".
How does compression help?
So where does this leave "compression"? Well, there are a few factors that help speed up imagery access when using compression
- Less data needs to be read from disk.
- The data is closer together. That is, it is packed more tightly, so the disk doesn't need to travel as far to collect the required information. It can find the information it needs faster.
And.... This is the big one, the "cost" of compressing is going to be pretty much irrelevant. The computing power growth that we are experiencing now and into the forceable future means that the cost of CPU will be virtually free. CPU Cores and speeds continue to grow at a rapid rate. Trading CPU against the speed of hard-disks is a winning proposition.
What about Solid State Disks?
Solid State disks are more similar to the "RAM" memory in a computer. They present the opportunity of faster disk speed. But, the reality is the technology isn't there yet. It isn't there from a performance side of things, and it isn't there on a cost basis. Maybe in a few years it be an option, but the performance needs to increase and the price needs to come down.
Imagery growth...
Even with the increases in size of disk size, can it keep up with the rate and size of data capture? New capturing technology makes higher resolution imagery more available than ever. So, can the size of hard-disks keep up with this? I would say, not without the help of compression.