LinuxQuestions.org - dmesg fusses about hard drive

I think it probably is.

Here's what I got:

Code:

nv_sata: Secondary device removed

nv_sata: Secondary device added

ata4: command 0x35 timeout, stat 0x51 host_stat 0x1

ata4: status=0x51 { DriveReady SeekComplete Error }

ata4: error=0x04 { DriveStatusError }

sd 3:0:0:0: SCSI error: return code = 0x8000002

sdd: Current: sense key: Aborted Command

    Additional sense: No additional sense information

end_request: I/O error, dev sdd, sector 625142272

raid5: Disk failure on sdd, disabling device. Operation continuing on 4 devices

RAID5 conf printout:

 --- rd:5 wd:4 fd:1

 disk 0, o:1, dev:sda

 disk 1, o:1, dev:sdb

 disk 2, o:0, dev:sdd

 disk 3, o:1, dev:sde

 disk 4, o:1, dev:sdf

RAID5 conf printout:

 --- rd:5 wd:4 fd:1

 disk 0, o:1, dev:sda

 disk 1, o:1, dev:sdb

 disk 3, o:1, dev:sde

 disk 4, o:1, dev:sdf

warning: many lost ticks.

Your time source seems to be instable or some driver is hogging interupts

rip __do_softirq+0x3b/0xb0

EXT3-fs error (device md0): ext3_free_blocks_sb: bit already cleared for block 69659407

Remounting filesystem read-only

md: unbind<sdd>

md: export_rdev(sdd)

md: bind<sdd>

RAID5 conf printout:

 --- rd:5 wd:4 fd:1

 disk 0, o:1, dev:sda

 disk 1, o:1, dev:sdb

 disk 2, o:1, dev:sdd

 disk 3, o:1, dev:sde

 disk 4, o:1, dev:sdf

Now, http://www.captain.at/howto-linux-dr...tatuserror.php suggests that there's nothing wrong with the error messages

Code:

ata4: status=0x51 { DriveReady SeekComplete Error }

ata4: error=0x04 { DriveStatusError }

and normally I'd be happy to just ignore it and wander off, but for two things:
1) While I definitely have backups of the most important data on this RAID5, I just did a lot of coding today and would lose a fair amount of work. I assembled this array for the performance (of which there is plenty) and for the safety (which I would like to improve).
2) When this little hiccup happened, /dev/sdd went out of sync. This is most distressing; I'm imagining a situation in which two drives do this simultaneously.

Needless to say, I'm not playing around with this. Another drive of appropriate size has already been ordered from Newegg. However, after taking that little security measure, I'd like to know the specific nature of this problem. Is /dev/sdd unreliable? Was this caused by some software glitch that I can fix? Is it a configuration problem? Most importantly, what can I do to keep this from happening again?

Thanks for reading and for your time. Cheers!