Time Machine times-out on external USB disk, but works on 2 others

Question

Hello,
I wanted to share my experience, in case it is helpful to someone else. It appears that one of my external hard disks has a hardware fault, or that TM is overly sensitive to its state, thus preventing me using it for backup.
After upgrading from Tiger to Leopard on my Macbook Pro 2.16GHz, I had been trying over the last couple of days, without success, to backup using Time Machine to an external USB hard disk at work. It is a Maxtor disk in a BlueEye U235 case. On each attempt to make the initial backup, TM would copy between 2 and 25GB of data (of 75 total) to the disk, and then stall indefinately, without giving an error. (Ejecting the disk at this point and restarting the computer just lead to further problems with completing the backup that I won't go into here). I tried many times, each time reformatting the disk (with the GUID partition map), deleting the TM preference file, restarting and ensuring all other apps were not running. I was completely fed-up!
I subsequently tried backing up for the first time on a freshly re-partitioned (GUID map) Firewire 400 external disk (Prolific PL3507 Combo Device in a BlueEye O2 case) at home, and this worked perfectly the first time, taking a couple of hours. (All applications were closed at the time). Subsequent backups to this drive work fine.
I tried again with the disk at work and it continued to fail. Finally I decided to follow what was being thrown up to the system.log. I discovered that shortly after TM was stalling (somewhere between 10 and 40 mins after commencing the backup), repeated messages would appear in system.log saying "kernel IOSCSIPeripheralDeviceType00::setPowerState(0x4cbe100, 2 -> 1) timed out after 100683 ms" (with the "2 - > 1" and number of ms different each time), with a few minutes between each one. This suggested to me that there was some sort of intermittent failure of the disk, or the connection between the Macbook Pro and the disk, or something I don't understand. It is worth keeping in mind that this disk has been working perfectly for me - I've been backup up entire system to it every couple of days using SuperDuper, without any errors or problems.
So, I then tried using a different (LaCie) Firewire disk at work, and after reformatting / partitioning (GUID map), the backup to this worked perfectly the first time, with the entire ~68 GB completing in about 2 hours. (As an aside, switching between the TM backup disks at Home and Work works well - TM just catches up from where it last left off on the particular drive).
The message I wanted to convey is that, in my experience, TM may fail during a backup (stall in fact, as no explicit message was generated) to a disk that outwardly appears to be fully functional. I'm not sure if in my case there is a minor error with the disk, a fault with TM, or both. Interestingly, upon bringing the disk home today and switching it on it won't mount at all, on my computer or that of my partner. I'm not sure if the problems with TM were therefore indicative of imminent disk failure, or whether the trip home in the pannier on my bike has damaged the drive . So, if you're having this or some other difficulty, on a drive that you haven't purchased new, it may be worth considering that an unsuccessful TM backup may be due to a current, or imminent, problem with the disk.
Just my two cents worth.

Answer 1

Yes, I think you have a good point. The motivation for my post was just to make people aware - as there seems to be many people having problems with TM - that maybe the first drive you try, particularly if it is not new, may not work and that it is worth trying another if you can. Particularly in light of the fact that I didn't receive any explicit error messages, that is other than the one in the system.log file.
The USB disk was powered separately and was plugged directly into one of my USB ports (not via a hub). At the same time a USB mouse was plugged in. I think it is USB 2, but I'm not sure, and as it is not working now, I don't know how to check.
The rate at which data is copied to the two drives that work (via Firewire 400) seemed to be quite similar to the rate for the USB drive, until it bombed out.