Time Machine backup failure due to unavailable files on Mac

I see two oddities in your Etrecheck Report:

• Your external target drive for your failing backups:

disk4 - VendorCo SSD 3.0 2.10 TB

External USB Up to 480 Mb/s USB

disk4s1 - EFI (MS-DOS FAT32) [EFI] 210 MB

disk4s2 [APFS Container] 2.10 TB

disk5 [APFS Virtual drive] 2.10 TB

disk5s2 - SSD (APFS) (626.98 GB used)

Note the speed shown is 480 Mb/s, which is maybe ~ one tenth the speed of a decent SSD. You may be using a charging USB-C cable instead of a high speed rated USB-C data cable, which should get 5 Gb/s to 40 Gb/s (5000 Mb/s to 40000 Mb/s). So it might be you are using a USB-C cable not suited to SSD backups, too slow, as I had suggested in my earlier post.

• Another possibility is a low quality external SSD. Yours is identified as a "VendorCO SSD" with an odd size 2.1 TB. See this post, often counterfeit SSDs self identify as "VendorCO," which is a generic placeholder the true vendor's name. Where did you get this SSD from?

https://www.hdsentinel.com/how_to_detect_fake_pendrive_memory_card.php

https://www.facebook.com/groups/1397842270480207/posts/3815493112048432/

There are many online posts about "VendorCO" external drives that are fake SSDs or show very slow performance and incorrect disk storage.

Yours claims to be using 600 GB already -- but isn't this for your target backup drive, it should be dedicated to the backups, what is in that 600 GB of used storage. This seems anomalous also.

I would obtain a reliable known vendor SSD model and try it for your backups. Well known brands include OWC, Samsung, Western Digital, Seagate, LaCie, Crucial, Kingston ... there are many. Sold on sites like Amazon, Best Buy, BH Photo, etc.

bayardm wrote:

With a view to upgrading my 1 year old Mac to MacOS 26, I purchased a 2 Tb SSD to back up my 1 Tb system.

using Timemachine I started the back up and got an estimated 22 hr timescale. I left the PC running overnight, but when I checked this morning the back up had failed and I got a report that it couldn’t be completed as some files were not available. Can anyone explain any possible reason for this, as nothing from the original set up has been altered and only documents, images and music have been added?

Even slower SSDs handle 500 MB/s or faster. Which is 30 GB/minute or 1.8 TB/hour. So your backup should take 30 minutes or less, which matches my experience. It can take longer, maybe a few hours for 1 TB, when using mechanical (non-SSD) external backup drives. But 22 hours is excessive.

The only time I have seen this type of slowness has been on my work Mac on which my employer requires anti-virus be installed. Such security software dramatically slows down Time Machine backups, at least compared to my personal Macs. By factor of 10x or more. So what should take ~ 1 hour can take 24 hours or more, for the initial first backup.

Do you have any third party security or anti-virus?

Also, as noted by den.thed in the link they provided from Apple, some encrypted files cannot be accessed when the Mac is locked. Again, I have only seen this issue on that work Mac with the anti-virus software running in the background. I was able to "cure" it on that Mac by running a utility called "Coca" (available in the App Store or elsewhere directly) which apparently prevents the type of sleeping that makes those files unavailable. If you are concerned about your Mac being unsecured when Coca is active, you can still lock the screen which then requires a password to unlock. I have never seen this issue on any of my personal Macs, none of which have such security nor anti-virus software installed.

That error usually happens when macOS locks or sleeps mid-backup, making certain system or encrypted files temporarily inaccessible to Time Machine.

Even if you didn’t change anything, Sequoia’s background indexing, iCloud sync, or privacy permissions can also block a few files. First, make sure your Mac doesn’t sleep during backup, go to System Settings > Displays > Advanced > Prevent automatic sleeping when the display is off and toggle that on. Then, check that you’re using a proper USB-C data cable, not a charge-only one, since that can throttle transfers and trigger “unavailable file” errors.

Finally, try running EtreCheck or watching Activity Monitor for any processes (like Spotlight or Photos sync) hogging disk I/O during the backup. Once those are out of the way, Time Machine should complete normally.

What make and model is the external SSD..?

If the external SSD is formatted correctly and on a USB 3.0 or faster port.

Then the initial 300-400GB Time Machine backup should complete in less than an hour.

It's starting to sound like the SSD is not formatted correctly or is being blocked by the manufacture software.

To fix that, use Disk Utility to erase and reformat the external SSD "GUID Partition Mac / APFS"

see > Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Then select the SSD when automatically prompted or by setting it up in the Time Machine settings.

see > Back up your Mac with Time Machine - Apple Support

@steve626 has done an excellent analysis of the EtreCheck report. I agree completely.

One other items which @steve626 overlooked was how many times Spotlight has crashed.....24 times in in less than 24 hours. Unfortunately we don't know if the Spotlight crashes are due to indexing issues on the internal boot drive, or an external drive.....especially your VendorCo SSD which show 600GB of storage.

FYI, you do not want to skimp on a backup drive. You want & need a good high quality backup drive because you want & need the backup to be ready at a moments notice in case something bad happens to your files. You don't necessarily need the backup drive to be an SSD....a Hard Drive may be sufficient since since you only had a 2TB SSD for your backup drive. Don't get a no name drive. Even some name brand drives are not always the best these days.

I don't agree with @steve626 regarding Amazon, or Best Buy, or any site that is open to third party merchants & marketplace. Those third party merchants are unknown & may be scamming people (some may be fine, but too many are not....there is no way to tell them apart). If you buy directly from the Best Buy website, just make sure the item being purchased is actually from Best Buy and not a third party merchant selling through the Best Buy marketplace.

B&H mentioned by @steve626 is a respectable vendor. So is OWC.

FYI, some scammers who are selling fake & counterfeit drives are making it extremely hard to identify them. Some scammers are taking well respected name brand used worn out or failing drives & making them appear to be brand new. It is nearly impossible to tell they are used drives because the scammers have modified the drives' health information.....someone had to invent a special utility to be able to retrieve the true information from the drive (in the case I'm referencing it was a Hard Drive, not sure if the utility would work for an SSD). This is why you need to be very careful from whom you buy drives these days....in addition to the traditional issues of finding a quality product. Sorry, I cannot find the link to the article reporting this particular case.

I believe the VendorCo SSD is the main problem, but if a good quality drive also gives you problems, then you should look into those Spotlight crashes.

You may want to use Etrecheck to see if something running in the background is the cause of the slow transfer rates. By the way, even though it estimated 22 hours, those estimates can be very inaccurate, especially if many small files are copied as the Time Machine run starts up.

Using EtreCheck to Troubleshoot Potential… - Apple Community

There are various kinds and levels of "sleep" on a Mac, and all of them do lock the Mac, although if only the display is allowed to sleep and lock the device, the computer itself remains unlocked.

To check USB transfer rates, you can:

• Use Blackmagic or similar software but they must be configured to test the external drive transfer, most of these default to test the internal drive transfer rates.
• In the full System Report available from About this Mac ...=> More info ... => System Report the USB and Thunderbolt ports rates will be shown, typically 5 Gb/s to 40 Gb/s (e.g. 0.6 GB/s to 5 GB/s).
• IMPORTANT: if you are using a CHARGE USB CABLE not one rated for high rate data transfer, you may see much lower rates, USB-2 rates which can be only a few tens of MB/s which might be what you are seeing. Try a high quality Thunderbolt or USB-C data transfer cable or try a new one.
• You can simply copy some large folders back and forth and watch Activity Monitor for the transfer rates or time it your self. For instance, if it takes 60 seconds to copy 60 GB that is 1 GB/s which is reasonable for SSDs and high quality cables.
• You have two issues here, and I believe they are not related. The first is the slow data transfer, which could be because you didn't wait long enough to get a good measure of it, or there is some background process interfering, or there could be a problem with the external drive or the cable you are using. The second is the "unavailability" of some files during the backup, which may be related to something running in the background (try Etrecheck) or may be because your Mac goes into a locked sleep mode during the backup and cannot access certain files to back them up.

For basic Time Machine troubleshooting tips and solutions.

see > Time Machine troubleshooting on Mac - Apple Support

From your description:

It sounds like either third-party AV-ware or logout/lock.

see > If a Time Machine backup fails on Mac - Apple Support

bayardm wrote:

Well I deselected everything that would put my Mac into lock and still got a failed backup, after at least 10 hrs, due to inaccessible files. EtreCheck reports no problems. Although, if I connect my drive and open it up, it doesn’t show any content, possibly because there isn’t a completed backup. However, EtreCheck reports several volumes on the device all in the region of 300-400 Gb. I think I’ll just accept defeat and not upgrade to Tahoe.

Tahoe is the least of your worries here. The fact that you cannot make a good backup is very concerning if you have any important files on the internal SSD. There are a lot more new ways to permanently lose access to the files on the internal SSD due to all of the hardware, software, and security changes. Your first priority is to make a good backup of you system....assuming you have any important files stored on it.

You should post the complete EtreCheck report here so we can examine it for possible clues:

How to use the Add Text Feature When Posting an EtreCheck Report - Apple Community

@den.thed is also asking important questions, plus they have included a link to an Apple article on how to erase the whole physical external drive since the partition of the drive from the factory may cause some devices & operating systems & apps problems. If you don't erase the external drive using the instructions @den.thed linked, then that is definitely the first step to take.

I agree with the points HWTech made.

I should have noted a possible connection between the Spotlight crashes and the other issues with that external drive.

Regarding sites like Amazon, I always look for "shipped from Western Digital" or "shipped from Amazon" to avoid counterfeit product sellers. From Best Buy I have purchased many tech items but always brand name trusted manufacturers and the product always comes directly from Best Buy in original manufacturer sealed packaging. Or I often pick it up in my neighborhood but again, always in original manufacturer sealed packaging. I was not even aware of third party sellers on Best Buy, but I do see them on Amazon and I always avoid them for any tech items.

👍 steve626 and HWTech