Apple loves SSD [solid state device] storage, which is one of the darlings of the tech world right now. But the fact is that flash SSDs aren't going to replace traditional hard disk drives (HHDs) any time soon.

Why? They're much more expensive and most of us are continually increasing our amount of digital media so we need roomy, inexpensive storage.

Of course, if we all store our music, videos and other data (including apps and valuable documents) "in the cloud" as some predict, SSD-based computers might take the lead. But as I've said repeatedly (and I won't rehash that argument here), I don't think cloud storage is going to replace traditional storage, but will, instead, complement it.

That's why hot selling, SSD-based items like the iPad and the MacBook Air are rarely used as a primary machine. They're usually companions to a Mac or (gulp) Windows system.

There's no denying that the SSD has some advantages over the HHD. Mechanical failure is the main reason HDDs crash and/or die. Over time, the moving parts that make up a traditional hard drive just wear out. SSDs have no moving parts -- they use flash memory cards -- for data storage, so they don't conk out as often.

SSDs are also beloved by those who feel the need for speed. Start-up time and disk-read time is faster in SSD hard drives than in traditional hard drives. Hard disk drives must spin up at start-up and while processing data. With no disk to cue up, SSDs start and read data more quickly.

So the SSD market will continue to grow, but is and will continue to be a fraction of the overall storage market for the time being. The iSuppli research group (http://www.isuppli.com) says that in 2010 there were 662 million HDDs shipped compared to 7.2 million SSDs.

In a white paper titled "NAND: can meet the growing storage capacity demands of the laptop PC market?” (http://macte.ch/8ZLXa) Seagate says the market for laptop PC disk drives worldwide is 69 exabytes (EB) and is forecast to grow to 95EB in 2011. But last year, the flash industry only produced 11EB of capacity. And 90% of that went into consumer devices such as smart phones, ST cards and drives. It costs over $2 billion to build an exabyte of flash production capacity.

What's more, the average capacity of a laptop hard drive is forecast to grow from nearly 300GB in 2010 to more than 350GB in 2011, notes Seagate. Laptop users want more capacity, not less.

So look for SSDs to continue to grow even as HHDs continue to thrive. In fact, the foreseeable future should see significant growth of Hybrid Hard Drives, which combine traditional hard drive storage on magnetic platters with a complement of flash memory for fast caching. This allows frequently accessed data to remain instantly available, even faster than resorting to random access memory (RAM). Flash memory is made from non-volatile memory chips, which means it stores data bits without the need of a power source. This is in contrast to RAM chips that lose all data when power is cut.

-- Dennis Sellers