>>>>>>You were certainly right on that suggestion. The event logs showed many errors, including quite a few disk i/o errors. I will never know exactly how or when the problem began but I still suspect it was associated with the backup software. I ended up purchasing a new HD and restoring from an older backup, then copying only the newer files that were truly essential. The procedure was probably overkill, and took a week to fix (formated the new disk at least 3 times to get the restore done correctly), but everything seems to be working now. The down side is the lost productivity and stress; the up side is I have lots of disk space now :-)
>>>>>
>>>>>Glad you got it sorted.
>>>>>
>>>>>These days (mechanical) hard drives are incredibly cheap. If you rely heavily on a particular machine it's a good idea to have at least 2 hard drives in a mirrored (RAID1) array. Everything you do is simultaneously copied to 2 separate drives, not just one. If one fails, you're still OK until you can get a replacement drive and return to full redundancy. These days most new desktop motherboards support hardware RAID directly, as do the majority of boards less than, say, 3 or 4 years old.
>>>>>
>>>>>It's worked well for me; I've had 3 complete drive failures of WD Caviar Black 1TB drives since Feb. 2010, but zero data loss from any of those failures.
>>>>
>>>>Ah, that proves to me that those drives are not reliable. If it occurs that frequent, I'd not feel comfortable despite the RAID config.
>>>
>>>Anyone doing serious work on a computer should also have regular file-based and image backups. Those should also include offsite or cloud-based backups, to cover the case of total loss of computer and/or backup media due to theft, fire etc. There are only two types of computer users - those who are true believers in backup, and those who are about to become true believers.
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>>>I have multi-level disaster recovery in place. AFAIC RAID1 is just one of those levels; having gone through several drive failures I know it works. I actually feel more comfortable than if I'd implemented RAID1 and never had a failure, in which case I would not be sure it works. YMMV.
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>>PMFJI. You said that most desktop motherboards support hardware RAID directly. What if most work is done on a notebook? Do you know if some notebooks support it too?
>
>With laptops the main issue is physical space in the machine for a second hard drive, and power and data connectors for it. I believe some large, high-end "gaming" laptops can include 2 hard drives. In those cases I've seen 2 possibilities:
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>1. One drive is a relatively small but fast SSD for boot, OS and swap file. The other is a large capacity mechanical drive to store all of a gamer's "stuff"
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>2. Both drives are large-capacity mechanical drives configured as a RAID0 array ("high-performance" but unsafe)
>
>Any laptop motherboard that supports dual internal hard drives *probably* supports RAID1. However, in either case above you'd have to do major reconfiguration to implement RAID1.
>
>With RAID1, the redundant array capacity is the size of the smallest drive, so normally you use two drives of the same size. They should also have similar performance, in case 1 it would be a really bad idea to RAID1 a small SSD with a large mechanical drive. You'd need to replace one or the other. Case 2 already has 2 drives of the same size and type, but would require that they be wiped and reconfigured to RAID1 from RAID0, then reinstall everything. Some advanced imaging software might be able to image the RAID0 array and then resize it downwards to fit on the RAID1 configuration but I wouldn't bet on it.
>
>If your laptop has a high-performance external connector (USB 3 or eSATA 6Gbps) then I believe there are some external enclosures that can hold two or more drives configured in various RAID flavours. USB 2 is not fast enough; eSATA 3Gbps might be OK but is uncommon on laptops.

Thank you for detailed explanation. I will be replacing my notebook at some point in the near future and will consider buying one with dual drive capability. Although I do make almost daily backup of my current drive.