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I have a Hitachi 5K3000 drive (HDS5C3020ALA) 2TB drive in an external enclosure.

Today I installed an application and copied some data to it, and it is now almost completely full: Windows Explorer reports 34GB free out of 1.81TB total space.

For about 10 minutes it continually made a noise which was rather alarming to me. It sounded like the disk was being accessed, it would thrash for about 1 second or two, then pause for about a second, then start up again. It continued even when the drive was no longer being accessed according to Resource Monitor, and indeed even after I removed the device via "Safely Remove Hardware" this continued until I powered it off. I carefully picked the drive up while it was doing this and I could feel a slight vibration as it made the noise. Surely it was the read head moving across a large portion of its range. I also noticed that during the actual thrashing the HDD activity light was not active but it came on during the second-or-so pauses.

And so it went like this for a good 10 minutes, me not being sure if my drive was slowly dying. I installed HD Tune and was slightly relieved to see no SMART warnings. I have no means of backing up this much data: It would never be worth the cost. So if it was going to die, the data would die with it.

And then all of a sudden it just stopped. Blissful silence.

I run Windows 7's disk defragmenter utility, and analysis reports 0% fragmentation on this 98.2% full drive.

So is this the explanation? Modern hard disk firmwares now defragment automatically? Does this mean that disk defrag software has now become completely obsolete?

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Note that a USB drive is different from a directly-attached drive. The USB drive has an on-board processor, and these vary in sophistication. To one degree or another they manage the disk and present a high-level view of the disk to the OS. (However, I've never seen a good description of how this "high-level view" is structured.) – Daniel R Hicks Mar 7 '12 at 17:16
In this particular instance I had the enclosure connected to my computer via eSATA. – Steven Lu Mar 8 '12 at 10:13

4 Answers

up vote 6 down vote

No, they don't do that, though Windows runs defrag by default from time to time automatically.

Your HDD activity can come from various sources, OS indexing your files for search on the new HDD, anti-virus software doing some random scanning etc...

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AV program access would show up in resource manager. I'm sure anything else the OS is doing with it would stop once I "Remove Device" and make it ready to unplug. But this activity continued even in that state. – Steven Lu Mar 7 '12 at 16:06
up vote 2 down vote

They do not defragment automatically. Hard drives are ignorant of any arrangement of the data other than a given LBA = 512 or 4096 bytes.

Hard drives do have the capabilitiy to conduct self tests for SMART, and I believe they do this periodically - would guess some do this by default.

Other possible explanations:

  • Hard drive firmware bug - you might try seeing if a firmware update is available
  • Possibly some miscommunication or subtle incompatibility between the enclosure chipset and the drive - maybe the drive received some mistakenly received some weird command to do a test or something similar. Entirely possible for some drives to simply "not like" some enclosures.
  • Read about hard drive error recovery - maybe the hard drive encountered some kind of error condition and was unresponsive to the enclosure chipset for too long, and the enclosure chipset is trying to reset the drive.
  • Possibly the heat from the drive has degraded the enclosure electronics.
  • Your drive really is dying.

If you do find a firmware update for your drive, DO NOT try to apply the update over the USB enclosure. Directly connect the drive.

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up vote 1 down vote

Windows 7 has the Disk Defragmenter software on a schedule. By default it occurs once a week. Some drives still need to be defragged. Solid State Drives do not need this and would actually hurt the life of the drive. There is no software in the platter drives that auto defragment.

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I turned defragmentation scheduling off. Note this activity started immediately after I made changes on the drive. – Steven Lu Mar 7 '12 at 16:08
up vote 0 down vote

NTFS nowadays uses space reservations, thus copying big files they are highly likley to avoid fragmentation Also any small (512) allocation will caouse 512k continuous allocation.

Windows defragmenter will not defragment drives with less than 20% free space (10% after reserving MFT)

You can get a better insight with defraggler or jkdefrag.

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I'd like to point out that each answer seems to add more contradictions to the evidence I have provided. On one hand I'm glad my drive isn't dead yet, but something definitely isn't adding up. – Steven Lu Mar 7 '12 at 16:43
1  
Defraggler does show me that the files I added on most recently are in fact somewhat fragmented. I guess what the drive was doing may remain a mystery after all. – Steven Lu Mar 7 '12 at 16:48
Drive does not do anything, it just stores data blocks and then gives back. Most notably it lacks intelligence of what filesystem or even partitions are on it. NTFS MFT gets badly fragmented when use exceeds 12,5% free space (or gets close to that). – ZaB Mar 8 '12 at 0:27

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