Puzzling Hard Drive Performance

[SpellowHouse]

What can cause a mechanical hard drive to perform like this....



The speed is acceptable but keeps dropping and in some cases will drop to zero for several seconds. The snapshot was taken when it was in the process of falling to zero (I missed the zero, but 4.64 is pretty close!).

What's really puzzling about this is that I have an identical PC and the other one is doing the same thing. If anything, it is a little worse ( they are mirrored so identical everything including HD content).

I don't think it's down to the PC, because I have SSD's in there, and they are performing just fine. It also isn't a read problem, it's a write problem. Reading is just fine.

The drives are about half full. Could this be something to do with it?

 

[jrwagh333]

Lots of small files?

 

[Armageus]

SMR drive?

 

[Donnie Fisher]

A lot of spinning drives have a flash based cache that buffers writes before they are committed to the spinning platters . So for general low size writes you’re effectively using an ssd. But for longer consistent writes it’ll be flushing out the cache to the platter and whilst doing so it’ll maybe struggle to accept more data in… so windows sees the slow down in write speed from its end.

That being said it should sustain faster speeds than what you see… unless it is an SMR drive.

 

[Rroff]

There are quite a few potential reasons including error correction (either drive, cable or interface) and things like small files and buffers like above but recent updates to Defender/Malware protection engine seem to be causing some issues with file copying - if I disable it I get expected speeds always, enabled at times speeds can be all over the place and stall at random either for a short period or indefinitely especially when copying large numbers of files. I'm also finding lately occasional false positives where Windows 10/11 will quarantine files mid copying I've 100% created myself and are not malicious.

 

[Murphy]

Could be any number of things from the type/design of the HDD to the type of files being transferred.

Are you able to say what type and size of the file (ISO, RAW, GIF, etc) it started to write to the drive right before and after it fell to zero?
How fragmented are the files on the drive?
What's the model number of the HDD?

 

[CaNsA]

Destination cache getting filled/emptied and the source drive having a higher priority access request to fulfill could be a cause.

Reads are generally faster than writes.

Source be all like "have all the things"
Desto be like "nice one, I can keep some of this here while I write the goodies"
Desto then be like "oh damn, so much stuff, slow down, stop"
Source be like "lame"
Desto "I'm good now"
Source "pathetic, here we go again"

 

[OliverQueen]

That explains the issue I was seeing last night backing up a RAID 0 (yes I know, I know!!!) array of 2 x Seagate Barracuda 3TB drives. Transferring 5.7TB of data from the drives to a 8TB USB3.0 via a USB3.0 port on the machine was showing 24MBps sustained, which I put down to moving 900GB of MP's, but when it got to the MKV's I took off my BluRay collection for Plex, it didn't change! I left it overnight & 12hrs later it was still showing 1 day remaining!!! Stopped the backup transfer & plugged the external drive back into the old 4770K machine where it usually sits as a network share & restarted transferring the remainder of the data. Was seeing sustained 110MBps (Gigabit network) transfer for first few hundred GB of files, then it dropped again ranging between 3MBps & 23MBps. Left it again for a few hours & again said it would take a day to finish!!! After a few hours I rechecked it to find that the transfer had dropped to 711KBps & basically stalled. Again stopped the transfer & run a CrystalDisk Info where the array didn't show (as it used to before). CrystalDiskMark though could see it. Opened up HWINFO to check & noticed that one drive was showing SMART Uncorrectable Sector Errors. Now running some utilities to test the drive out before I end up losing the data I haven't backed up as don't really fancy backing up the BluRay's that will be missing again!!!! Have to admit though that these drives have been running 24/7 for past 6 years & the data gets accessed a lot by myself & wife, so had money's worth from them.

After reading the comments & checking, these are also SMR drives - which not too happy about as was not made aware of this in any documentation until today... Looking at the market unless spend a bit more on Barracuda Pro drives, all the basic HDD's are SMR nowadays if 2TB & larger. Same with WD RED NAS drives (which I ordered as replacements before reading this thread ). Nor to decide if I should return them or not when delivered, or just say "Koof It" & use them as single drives/RAID1 (& lose some storage space)

TL/DR: Might be worth checking the SMART functionality of the drive for errors. No warnings from BIOS/UEFI SMART monitoring either!