When you decided where to live you had to make some conscious decisions. You had to decide where your house was in relation to things that are important to you – schools, the office, transport hubs, freeways or motorways.
You had to decide based on your method of transport how close you needed to be to those things so that your experience was acceptable or great. If you worked in New York, it would not be practical to live in beautiful New Zealand as the commute just wouldn’t work unless you could work remotely. So location is important for things that are important to you.
Storage works in much the same way. A traditional HDD has many platters and the data is typically accessed on the drive from the inside of the platter to the outside of the platter. Physics is physics so information on the inside smaller section of the platter will be quicker to read/write than information on the larger outside.
Back in the old days, DBAs would have to really think about placement of data. Either by specific spindle and RAID allocation or even getting down to block location on disks. Seek times on the inside of the platter were faster than the outside, so that is where high-performing tables and things like temp-DB needed to live.
Memory has really helped that issue, so has other forms of cache so long as the blocks that need to be cached can fit in the amount of allocated memory or cache, if not you hit a latency wall as you have to go off and seek from disk. This means your reads are essentially free, but writes still require some overhead and I/O tax.
SSD really does go a long way to resolving those issues. SSDs and other flash media are locality reference free! Essentially they are binary charges off and on that means that they are basically free for reads and writes which is why IO latencies are typically sub millisecond.
DBAs now no longer need to worry about where and how they place their data or even if they used share storage. DBAs will always worry, but now they can worry about things further up the stack.
Imagine if you could live in beautiful New Zealand, work in New York and holiday in the Caribbean without the challenges and cost overheads of mechanical travel. That is what locality free data access with SSDs and the right Storage OE can give you.