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Pastimes : Dream Machine ( Build your own PC ) -- Ignore unavailable to you. Want to Upgrade?

To: Clarence Dodge who wrote (7101)	4/17/1999 8:33:00 PM
From: Spots	Respond to of 14778

>>So the point at which damage occurs ... It would be hard to damage a drive physically by powering it down, but logically is another matter. It depends entirely on what the OS is doing with it. If, for instance, you were to save a large file and suddenly turn the PC off in the middle, would you expect damage? Would you expect to be able to recover the file? Would you think the index structure could possibly be damaged? I would think all of these. If I had disk cache enabled, one does by default in NT (I don't know how to turn it off, anyhow), and I had done recent operations on the disk, possibly involving the index structure, would I expect them to be written to the disk? Only if I were a more trusting sort than I am. Put it another way: Unplugging the disk is like any other sudden power outage. Assuming it wouldn't cause physical damage like a power spike (which IS an assumption, based on your perceived effectiveness of the connection), it could definitely cause the same damage any other kind of sudden power outage could. >>How do scsi drives react differently when switched hot? I don't know that they do. I think you're confusing hot- switching backup drives with hot-switching drives with active file systems. These two things are not even close. Suppose I have a drive fail. That means automatically I'm not worried about the data on it anymore (insofar as switching is concerned), I'm worried about getting its capacity back on line for my users. THEN I can talk about hot switching spares into my system. OR, if I have a fault-tolerant setup, hardware or software, I have maintained my users' data, and I'm concerned about restoring fault tolerance in case another fault occurs. Either way, from the point of view of switching, the data on the drive switched out is toast, and the data on the drive switched in is irrelevant because it's going to act as a brand new blank drive. IF I have mirrored drives, or drives in more sophisticated fault-tolerant arrays (higher RAID numbers), THEN I can think about hot swapping backup drives without loss of data. That's because the disk controller handles the swaps (for controller based fault tolerance) or the OS handles the swaps at a level below the logical file system (for OS based fault tolerance). The important point is, in the one case the hardware, software, or both, KNOW at some level about the swap. In your case, none of them do except the electrical level. Sum it up: You're dancing with disaster, and sooner or later, disaster will make you a full partner. At which point, look in the mirror and tell that guy "That's your fault." <ggg> Spots