@Bob, yes you're completely right. This kind of engineering is what you get when buying a 2540 for example. All parts are nicely matched. When you build your own whitebox the parts might not match.
But that wasn't my point. Vibration, in the drive and excited by the drive, increases with the spindle speed. Despite fluid bearings or other measures, the platters are always imperfect. And at some point this imbalance can no longer be compensated for. Result vibration. The amount of energy stored in the platters increases, I presume squared, with the spindle speed. So at higher speeds the effect will get greater. Now back to the resonance. If all drives are vibrating AND in sync than nice standing waves will ripple through your chassis. I've seen this, ages ago, in the extreme on arrays were the drives were synced by an external clock signal. This was specialty hardware with a HIPPI interface. Certain modern drives have circuitry to prevent this. Still preventing the vibrations in the first is easier with lower speeds, a non revolving disk will emit zero vibrations. It's mechanically easier at 5400rpm than at 15000rpm. No vibrations equals no drive induced resonance. Back to the topic. Since TLER/ERC/CCTL drives usually have this feature as well. And I know the difference between the drives with and without I thought it would be relevant for the discussion. Regards, Frederik -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
