Postby shooraijin » Fri Oct 07, 2005 8:00 am
Volt, there's *nothing* different about server hard disks. Same mechs, same platters, same bearings. The hard disks we used in the HP minis and Sun servers at my old job were the same ones in the W2K servers and the same ones in the workstations.
Yes, over time, the bearings will wear. Over a long time. The Apple Network Server 500 in my apartment has been using the same drive for almost 10 years (an 18GB Fujitsu 7200rpm SCSI-2), and other than when I moved it up here and during a server retrofit a couple months ago, it has been running continuously. If anything, the ground strap (the part that squeals on really, really beaten-up drives) will wear long before the bearings do. All hard disks have an MTBF and estimated service life for running at speed. If you buy a lousy one, these statistics will be lower, if the vendor computes them at all, and the drive craps out sooner. But most vendors measure this in hundreds of thousands of hours.
Heat also kills drives. I have central A/C, so no problem.
Also, while the bearings will slowly wear during constant revolution, it's a greater mechanical stress during changes in velocity because, for example, in powering up you have to overcome friction at rest to get the drive spinning. This will cause greater forces on the bearings than the constant low-friction spin of an already-powered-up drive. In fairness, vendors do rate drives for start/stop cycles, and you'd have to be banging the drive several times a day to reach these conservative numbers, but you'd exhaust this quicker than even a real-world-proven MTBF or vendor-estimate service life for a drive just left spinning.
As for everything else, why do light bulbs only pop when you turn them on, not when they're already running? Thermal expansion applies to other electronics, not just light filaments. For that matter, hard disk electronics are subject to the same thing, as well as the rest of your motherboard.
EDIT: I should say, in the interest of equanimity, that I only leave computers running all the time that need to be. The servers have to be on 24/7, and my dualie G4 gets so much use that it might as well be (and I even access files from it on the road, so there's another reason). However, all of the other systems remain off unless in use. A powered-up system is vulnerable to power surges and spikes (the servers and the G4 are all connected to UPSes, but not everything else is), and having a lot of systems powered up wastes electricity and generates lots of heat. So weigh your needs and the risks and benefits.
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