My recently bought HGST 7K1000 HTS721010A9E630 hard drive is occasionally making normal quiet activity sounds, but in periodic short bursts lasting (hard to say…) from 0.1 to 0.5 seconds and occuring every 1-3 seconds. The "pattern" or "rhythm" of these sounds is rather equal during each "session" or "occurence" of these bunch of short bursts. So, for instance, at one time the bursts lasted about 0.1 seconds and pauses between them were about 1 second, at another time it was about 0.5 seconds with pauses of about 3 seconds.
In other words, it probably reads and/or writes something each 1-3 seconds. I ran Windows Resource Monitor and Sysinternals Process Monitor, but I couldn't detect if any program is using the drive. Right now the drive is "ticking" like this, but the Resource Monitor doesn't show any activity on that drive.
HGST Windows Drive Fitness Test (WinDFT) reported no errors. CHKDSK failed and said "An unspecified error occurred". Probably it failed because the partition is encrypted, I think.
For example, while WinDFT was running the extended test, there were no sounds. After I ran TrueCrypt and mounted the volume stored on the drive, the drive began making these short sounds (bursts of activity) with intervals of about 1 second, so if you didn't know the source, you could easily think that it's a small clock or a wristwatch.
I'm using a partition encrypted with TrueCrypt, but when I dismount the TrueCrypt volume and close TrueCrypt, the "ticks" remain the same. There are no active background processes or services of TrueCrypt.
The first I've noticed this was when I was copying many files of various sizes to the drive. I was copying them in portions, and between these portions, when the drive should be inactive, I could hear these bursts of activity. I thought that this has something to do with write caching and disabled the "write caching on the device" in the device properties window, but this didn't change anything. Well, why would it – who would cache the data for so long and then flush it in small portions over, say, half an hour – that's absurd.
Also, I wanted to create a different (but related) Super User question about why this hard drive is making some strange sound, probably caused by spinning of its parts, after the computer is powered off. I never heard anything like this, but I don't have much experience with laptop drives and have no experience with HGST drives, so I hope that it's a normal sound.
I can try to record all of these sounds and upload them, so that my question would have more substance. I'd like to mention, that when the drive is really in use by some program, the "ticking" disappears temporarily.
Another example and somewhat interesting fact: as I said, the drive was making these periodic short activity sounds with intervals of about 1 second even after I dismounted the TrueCrypt volume. When I mounted the volume again in about 20 minutes, the drive became silent. After about 3 minutes the "ticking" started again.
My first experience with magnetic storage is dating about 20 years back, and my instinct is telling me that periodic sounds of unknown nature are a sign of trouble, even if it's the sound of reading or writing, because often such periodic reading is done when the drive fails to read something.