Question HDD speed inconsistent

Mar 26, 2023
I have a Seagate ST500LM021 500GB 7200RPM (Second hand drive and I got it yesterday) drive and my drive speeds are inconsistent as hell. The first time I got this, the speeds were around100MB/s read and 80MB/s write and I thought that was normal but I restarted, it suddenly dropped to 30-40MB/s read and write. I opened my PC to make sure that cables were plugged in correctly and stuff, after that I ran a test again and now its 100MB/s read and 50MB/s write(Picture shown below)? From this post I saw, It says that 100MB/s read and writes were normal. I think it's because of the temperature (My PC is a compact form factor so everything is kinda squished together) because the 2nd test I ran after I restarted that was 30-40MB/s read and write, my PC was quite warm and the 3rd test I ran (With the picture shown below), I let everything cool down for a little bit( According to CrystalDiskInfo, my disk is at 36 degrees Celsius )
Nothing at all wrong with 36 degree temperatures on a hard drive.

I'm not sure I ever heard of an HDD slowing down because of temps, could be I suppose.

Varying results from a hard drive can be due to the size of the individual files as well as the drive's caching capability.

You can get all kinds of results from Crystal Disk Mark depending on which of its many tests you choose to run from the menus.


If there's a problem with the hard drive, it would be extremely unlikely to be a temperature issue, and even in that extremely unlikely case, we're probably talking actual high temperatures. There's no reason for a hard drive to have an issue because of temperatures that aren't even typical human body temperature.

When you buy a cheap second-hand hard drive, and probably one that is really old, you should just be happy it's working and not riddled with bad sectors, and not spend time worrying about inconsistent write speeds. It's a slow, old drive at either speed and the type of files you're transferring will be a larger factor in its performance.
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Feb 4, 2019
Copy speed depends largely on "what type of files" are being copied, moved!

I have never seen consistent speeds, but just having said that I always get the feeling that my 100% working drives and OS are cheating me out of possible performance!

It's almost as if the OS, witch ever one, is always intentionally slowing down such tasks to save either the hardware or the power that would be utilized if it were to go maximum, witch rarely happens on varied tasks of moving or copying.

It's really quite the funny business, hardware manufacturer's ad's stating that one can finally get out from the slow speed always observed with mechanical drives or ssd's when you purchase a nvme, just to be haltered again by limited performance once you start utilizing the newest drive tech, but the thing that really happens is the difference in file types being copied, moved it seems, but sometimes like I said above, this observation makes one think twice if there isn't some other missing link to the whole speed equation that we don't know about.

On the other hand, don't forget that one gets very quickly used to your current speed, even if you have new tech, and that's why you get the feeling that it isn't going as fast as it should, it's either that or there is an underlying hardware or software fault.
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. . . . my drive speeds are inconsistent as hell. The first time I got this, the speeds were around100MB/s read and 80MB/s write and I thought that was normal but I restarted, it suddenly dropped to 30-40MB/s read and write.
So, nothing about what you write can be seen as a clear indication of any failure. On the contrary - since you don't go in further details on your test procedure, I can only assume that you're either measuring raw R/W performance at the inner portion and outer portion of the platters - or as already mentioned, there is a mix of small and big files, or both. Or it can be you performing a benchmark on a hdd where your windows is installed on, that last thing will cause performance hits as Windows need to interact with the hdd all the time, and will cause perceived performance drops if benchmarking that disk.

So, lot of explanations on this other then "it must be defective hdd".

However, I recommend you trying to run a disk benchmark using a proper tool.
  • HDTune - freemium software, can use unpaid version for limited time. This program create a time/performance graph so that you can spot if there is performance drops that doesn't fit the curve.
  • If you have Windows installed on that same hdd, then a benchmark cannot be properly performed on that hdd. One solution i to use a Linux Live-desktop (try without installing). Most Linux distros does include this "Gnome disks" utility (most often just named "Disks" in program menus) that is capable of performing similar benchmark as HDTune.
I also recommend you get the s.m.a.r.t. values from the hdd, as there should be information in there that can tell if the HDD is in bad shape or not.