A year ago, you'd be forgiven for confusing Western Digital (NYSE: WDC) with Seagate Technology (NYSE: STX). Other than the fact that Seagate served more corporate accounts and fewer consumers than its hard-drive-maker twin, the two companies were pretty much interchangeable.

Today, you can tell a difference. Both companies reported earnings over the past few days; Western Digital's shares have dropped 8% in five days while Seagate jumped 22% today.

So what gives? Sure, Seagate's first-quarter results looked fine, with $0.34 of non-GAAP earnings per share on sales of $2.8 billion. These are modest single-digit growth figures year over year despite a difficult global economy. But that's not the real story.

Instead, storage investors are focusing on how the two companies deal with the ongoing flood damages in Thailand, which happens to be the second most important drive-manufacturing region in the world after China. And as it turns out, Western Digital has taken more damage than Seagate, which will take longer to repair.

In fact, Seagate's facilities are largely operational -- the main damage to this company's operations comes from component manufacturers that weren't as lucky. The affected suppliers are mainly mechanical-parts specialists like TDK, not storage-chip experts such as Marvell Technology Group (Nasdaq: MRVL) or Atmel (Nasdaq: ATML). This is also why Xyratex (Nasdaq: XRTX) is surging this week, as damaged manufacturing facilities will need new equipment that Xyratex sells.

So the Wonder Twins of hard-drive storage weren't quite as identical as they might have seemed. If 2011 has taught the IT industry anything, it would be not to build factories in flood zones.

The lack of cheap hard drives could boost demand for solid-state storage devices. Keep a close eye on the hard-drive guys and on SSD specialist STEC (Nasdaq: STEC) to monitor the situation. Our Foolish watchlist can help:

Fool contributor Anders Bylund holds no position in any of the companies discussed here. The Motley Fool owns shares of Western Digital and Marvell Technology Group. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. You can go over Anders' holdings and a concise bio, follow him on Twitter or Google+, or check out our Foolish disclosure policy.