If the hard-drive fails on the PS3 you may get a solid yellow led, this is referred to as the yellow light of death in response to the infamous red ring of death.
The yellow light will show if the console is overheating as well, but the console shuts down so you don't it for long.
The PS3's overall failure rate is about 1% and hard drives, although mechanical, have a very low failure rate (over million hours mean time between failure, so on average your hard drive would fail every 114years) which means you are very unlikely to see a YLOD, however one in three XB360 owners are unfortunate enough to see the RROD first hand.
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You hit the one percent chance four four times?