Horrible performance deleting files on external disk

TidBITS Talk
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I spent some money a few years back to purchase a “OWC Express 4M2 4-Slot NVMe M.2 SSD Enclosure” with 4 x 2TB NVMe M.2 2280 cards. It tests at well over 1,500 Mb/s read/write.

I put a bunch of large files on it, then deleted them. They are deleted (by Finder) at a rate of about 1 file every 5 seconds. AFAIK, the only thing Finder is doing is moving the files into the Trash folder.

Have I run into the known performance hit of formatting external disks as APFS? Should I erase this disk and reformat as HFS+?

Any advice welcome.

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Not an expert, so I’ll be interested in someone’s better advice.
But my 2 cents would be sort of an awkward/longer work around.
I would copy the files I want to Save to another drive, then erase the ssd drive.
My understanding is that it is still “better” to format ssd drives as apfs

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I wonder if Spotlight is a factor? Or perhaps the RAID software that consolidates the multiple SSDs?

It might be interesting to try the rm [remove] command in Terminal as an alternatve (but be very careful with that command).

(I wouldn’t change an APFS SSD to a different file system).

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There are a few things that might be happening, ranging from the relatively benign to very serious. Some things to consider:

  • Check the free space on your boot disk. I have noticed that when a Mac’s boot disk is getting full (around 1-2 GB free space or less), a lot of basic operations can become very slow.
  • Power down the Mac, disconnect the external drive, and then reconnect the drive.
  • Try a different cable to connect the drive.
  • Run First Aid in the Disk Utility app.
  • What kind of files are you trying to copy? Some “files” are actually bundles of thousands of files, which can make them take longer than expected to copy. For example, the GraphicConverter app is only around 600 MB, but it is a bundle of almost 14,000 files that appears as a single file to users. If I copy a 600 MB zip file, it happens so fast I barely notice it, but if I copy the 600 MB GraphicConverter app, it can take a few seconds because of the extra work involved in copying thousands of hidden files.
  • Of course, there may be a more serious problem with either the filesystem or the drive. If it is feasible, I would consider @jmhbpc’s advice of copying files elsewhere and then reformatting the external filesystem.
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Thanks all.

  1. I can’t imagine that spotlight is a problem. These are all tiff files.
  2. These are not bundles, they are tiffs
  3. The disk is ~ 25% full
  4. There isn’t any detectable problem with the file system
  5. The disk is very fast, it is just deleting large files that is slow

I suggest that everyone read the article by OWC that I referenced in the O.P. They really know what they are doing, and they strongly suggest that you never format an external disk as APFS unless it is being used for Time Machine. I suspect I should have followed their advice. If I reformat this disk, I’ll let you know my results. But, as they say, it takes weeks or months for the problems to show up on APFS disks, so if everything speeds up with HFS+, that isn’t definitive evidence that I fixed the problem.

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I don’t think that advice applies to your situation, since you are using SSDs. The issue raised by OWC is well known, but I’m pretty sure it applies only to spinning hard disk drives (HDDs), not SSDs. Something else is going on. Have you tried contacting OWC support?

Edited to add: There are scenarios where SSDs can slow down over time after certain usage patterns. I don’t recall details offhand, but I’d research the general topic of slow SSD behavior in general.

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I wonder if TRIM could an issue here. After each file is deleted it is doing garbage collection. Still, it should not take that much time per file.

I agree with @macintouch.com’s advice to use the rm command. That removes the file and bypasses Finder.

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That applies to HDDs. Since you’re using NVMe flash (SSD), that’s not an issue and there is for you no advantage to HFS+ over APFS, in fact quite the opposite: APFS gives you several things you want that HFS+ cannot.

My money would be on the RAID as the culprit behind the degraded delete performance.

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Thanks, Simon, you are right. I forgot what the OWC memo actually said.

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Thanks all for your responses.

I erased the SDD, reformatted it as APFS (RAID 0) and restored the files, and now putting files in the trash and emptying the trash is instantaneous, as it should be.

I have no idea what caused the slowdown, but it only showed up for deleting files in Finder, all other operations (read, write, new files) seemed as fast as they should be.

My bet is still that APFS caused this slowdown, but I honestly don’t know, and I’ll never be able to show that without more effective testing and note taking than I care to do.

Again, thanks to all

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I think the OWC RAID software is a more likely culprit than APFS. It may lack support for SSD Trim, which could be an issue with deletions particularly.

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