Time Machine backup drive constantly being accessed.

[EugW]

This was new as of yesterday. My external Time Machine backup drive's disk access light was flashing as accessing all the time. It's a USB 3 portable bus-powered HD. Even after a backup was completed, it was still flashing as accessing the disk even several hours later. I made sure that the Energy Saver Prefs have "Put hard disks to sleep when possible" checked, and yes it was checked. OS is macOS Big Sur 11.6, on a 2017 i5 iMac.

I could access the backups, and I could force a backup and both worked fine. I rebooted and the drive was dormant... until I logged in and then it started accessing again. I again left it for hours and the same behaviour, even when it was not making a backup.

Finally I just deleted the drive and set it up again as a new Time Machine backup, and now it's working normally. As expected, it now goes dormant when not in use, and only gets activated as needed for backups.

What gives? What could cause the drive to be constantly accessed like that, for hours upon hours on end? Could it ever be a sign of drive failure?

---

On another note, my laptop lost the pairing with its Time Machine backup drive connected to an AirPort Extreme. It sees the drive, but wants me to set it up again as a new backup, and does not accept all the old backups on it. I think I'll just nuke that one as well and start over.

 

[Hombre53]

Turning on drive encryption would explain the activity, but that seems remote since you didn't mention that. The file system may have been damaged, hence the system may have been re-indexing or engaged in repair activity. Since you reformatted and set the drive up again, you probably solved whatever issue you may have had. A free after market app called
"DriveDX" monitors the condition of your drives and reports any issues or failures, soon or imminent. It's a free app, something you may want to look at.

 

[EugW]

Turning on drive encryption would explain the activity, but that seems remote since you didn't mention that. The file system may have been damaged, hence the system may have been re-indexing or engaged in repair activity. Since you reformatted and set the drive up again, you probably solved whatever issue you may have had. A free after market app called
"DriveDX" monitors the condition of your drives and reports any issues or failures, soon or imminent. It's a free app, something you may want to look at.

Thanks. No encryption.

I'll check out DriveDX.

On another note, my laptop lost the pairing with its Time Machine backup drive connected to an AirPort Extreme. It sees the drive, but wants me to set it up again as a new backup, and does not accept all the old backups on it. I think I'll just nuke that one as well and start over.

BTW, what seemed to trigger this was a replacement of a defective Ethernet switch. Even though it's just a dumb switch and nothing else on the network (including the settings on the AirPort Extreme) has changed, all of a sudden my Macs using it for Time Machine no longer saw it as their original Time Machine drive.

 

[EugW]

DriveDX says the drive is fine.

Spoiler

### SYSTEM INFORMATION ###
Report Timestamp                     : December 6, 2021 10:19:12 AM EST
Report Timestamp (ISO 8601 format)   : 2021-12-06T10:19:12

Application Name                     : DriveDx
Application Version                  : 1.11.0.730
Application SubBuild                 : 0
Application Edition                  : Standalone
Application Website                  : https://binaryfruit.com/drivedx
DriveDx Knowledge Base Revision      : 101/101

Computer Name                        : Eug’s Mac mini
Host Name                            : Eugs-Mac-mini
Computer Model                       : Macmini7,1

OS Boot Time                         : 2021-12-06T10:14:55
Time Since Boot                      : 00h 04m 17s
OS Name                              : macOS
OS Version                           : 10.16.0
OS Build                             : 21A559
OS Kernel Version                    : Darwin 21.1.0

SAT SMART Driver Version             : 0.10.3s
ATA Command Support Tolerance        : verypermissive
N of drives in report                : 1



### DRIVE 1 OF 1 ###
Last Checked                         : December 6, 2021 10:18:59 AM EST
Last Checked (ISO 8601 format)       : 2021-12-06T10:18:59

Advanced SMART Status                : OK
Overall Health Rating                : GOOD 100%
Overall Performance Rating           : GOOD 100%
Issues found                         : 0

Serial Number                        : 
WWN Id                               : 0 000000 000000000
Volumes                              : iMac Time Machine
Device Path                          : /dev/disk5
Total Capacity                       : 2.0 TB (2,000,398,934,016 Bytes)
Model Family                         : Toshiba 2.5" HDD MQ01UBB... (USB 3.0)
Model                                : TOSHIBA MQ01UBB200
Form Factor                          : 2.5 inches
Firmware Version                     : AY000U
Drive Type                           : HDD 5400 rpm

Power On Time                        : 6,591 hours (9 months 4 days 15 hours)
Power Cycles Count                   : 71
Current Power Cycle Time             : 0.1 hours



=== DEVICE CAPABILITIES ===
S.M.A.R.T. support enabled           : yes
DriveDx Active Diagnostic Config     : Base config [hdd.default]
Sector Logical Size                  : 512
Sector Physical Size                 : 4096
Physical Interconnect                : USB
Logical Protocol                     : USB
Removable                            : yes
Ejectable                            : no
ATA Version                          : ATA8-ACS (minor revision not indicated)
SATA Version                         : SATA 2.6, 3.0 Gb/s (current: 3.0 Gb/s)
I/O Path                             : IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/XHC1@14/XHC1@14000000/SSP4@14b00000/External USB 3.0@14b00000/IOUSBHostInterface@0/IOUSBMassStorageInterfaceNub/IOUSBMassStorageDriverNub/IOUSBMassStorageDriver/IOSCSILogicalUnitNub@0/fi_dungeon_driver_IOSATDriver/IOSATServices

Enclosure Vendor Id / Product Id     : 0x480 / 0xa200
SAT Pass Through Mode                : sat12
SAT SMART Driver Version             : 0.10.3s
SAT SMART Driver Bundle Id           : com.binaryfruit.driver.SATSMARTDriver
SAT SMART Driver I/O Class           : fi_dungeon_driver_IOSATDriver
SAT SMART Driver Architectures       : x86_64 arm 

Attributes Data Structure Revision   : 16
SMART Command Transport (SCT) flags  : 0x3d
SCT Status supported                 : yes
SCT Feature Control supported        : yes
SCT Data Table supported             : yes
Error logging capabilities           : 0x1
Self-tests supported                 : yes
Offline Data Collection capabilities : 0x5b
Offline Data Collection status       : 0x0
Auto Offline Data Collection flags   : 0x0
[Known device                       ]: yes
[Drive State Flags                  ]: 0x0


=== CURRENT POWER CYCLE STATISTICS ===
Time since computer startup         : 0 hours
Data Read                           : 128,109,056 bytes (128.1 MB)
Data Written                        : 2,723,840 bytes (2.7 MB)
Data Read/Write Ratio               : 47.03
Data Read/hour                      : 1.8 GB/hour
Data Write/hour                     : 38.2 MB/hour

Operations (Read)                   : 17,427
Read IOPS                           : 160
Operations (Write)                  : 308
Write IOPS                          : 3
Operations Read/Write Ratio         : 57
Throughput per operation (Read)     : 7.4 KB/Op
Throughput per operation (Write)    : 8.8 KB/Op

Latency Time (Read)                 : 0 ns
Latency Time (Write)                : 0 ns
Retries (Read)                      : 0
Retries (Write)                     : 0
Errors (Read)                       : 0
Errors (Write)                      : 0


=== PROBLEMS SUMMARY ===
Failed Indicators (life-span / pre-fail)  : 0 (0 / 0)
Failing Indicators (life-span / pre-fail) : 0 (0 / 0)
Warnings (life-span / pre-fail)           : 0 (0 / 0)
Recently failed Self-tests (Short / Full) : 0 (0 / 0)
I/O Error Count                           : 0 (0 / 0)
Time in Under temperature                 : 0 minutes
Time in Over temperature                  : 0 minutes


=== IMPORTANT HEALTH INDICATORS ===
ID  NAME                                         RAW VALUE                  STATUS
  5 Reallocated Sector Count                     0                          100% OK
197 Current Pending Sector Count                 0                          100% OK
198 Offline Uncorrectable Sector Count           0                          100% OK
199 UDMA CRC Error Count                         0                          100% OK


=== TEMPERATURE INFORMATION (CELSIUS) ===
Current Temperature                  : 27
Power Cycle Min Temperature          : 24
Power Cycle Max Temperature          : 27
Lifetime Min Temperature             : 19
Lifetime Max Temperature             : 49
Recommended Min Temperature          : 5
Recommended Max Temperature          : 55
Temperature Min Limit                : 5
Temperature Max Limit                : 55


=== DRIVE HEALTH INDICATORS ===
ID   | NAME                                        | TYPE      | UPDATE | RAW VALUE                  | VALUE | THRESHOLD | WORST | LAST MODIFIED        | STATUS          
   1   Raw Read Error Rate                           Pre-fail    online               0x0                100          50    100                       -    100%  OK          
   2   Throughput Performance                        Pre-fail    offline               0                 100          50    100                       -    100%  OK          
   3   Spin Up Time                                  Pre-fail    online              5,036               100           1    100                       -    100%  OK          
   4   Start Stop Count                              Life-span   online              8,749               100           0    100                       -    100%  OK          
   5   Reallocated Sector Count                      Pre-fail    online                0                 100          50    100                       -    100%  OK          
   7   Seek Error Rate                               Pre-fail    online               0x0                100          50    100                       -    100%  OK          
   8   Seek Time Performance                         Pre-fail    offline               0                 100          50    100                       -    100%  OK          
   9   Power On Hours                                Life-span   online              6,591                84           0     84                       -   84.0%  OK          
  10   Spin Retry Count                              Pre-fail    online                0                 253          30    100                       -    100%  OK          
  12   Power Cycle Count                             Life-span   online                71                100           0    100                       -    100%  OK          
 191   G-Sense Error Rate                            Life-span   online                55                100           0    100                       -    100%  OK          
 192   Power-Off Retract Count                       Life-span   online                39                100           0    100                       -    100%  OK          
 193   Load Cycle Count                              Life-span   online              9,442               100           0    100                       -    100%  OK          
 194   Temperature (Celsius)                         Life-span   online                27                100           0    100                       -    100%  OK          
 196   Reallocated Event Count                       Life-span   online                0                 100           0    100                       -    100%  OK          
 197   Current Pending Sector Count                  Life-span   online                0                 100           0    100                       -    100%  OK          
 198   Offline Uncorrectable Sector Count            Life-span   offline               0                 100           0    100                       -    100%  OK          
 199   UDMA CRC Error Count                          Life-span   online                0                 200           0    200                       -    100%  OK          
 220   Disk Shift                                    Life-span   online                0                 100           0    100                       -    100%  OK          
 222   Loaded Hours                                  Life-span   online              1,025                98           0     98                       -   98.0%  OK          
 223   Load Retry Count                              Life-span   online                0                 100           0    100                       -    100%  OK          
 224   Load Friction                                 Life-span   online                0                 100           0    100                       -    100%  OK          
 226   Load-in Time                                  Life-span   online               269                100           0    100                       -    100%  OK          
 240   Head Flying Hours                             Pre-fail    offline               0                 100           1    100                       -    100%  OK          



=== DRIVE ERROR LOG ===
error log is empty


=== DRIVE SELF-TEST LOG ===
#   | LIFETIME (H)   | TEST TYPE         | PROGRESS | STATUS                          | LBA of 1st error
1          6591        Short offline         100%     Completed without error              -

I wonder what caused the issue then. Strange. Anyhow, in the past several days since reformatting the drive and setting it up as a new Time Machine backup, it's been fine.

 

[EugW]

Initial Time Machine Backup Failures Increasingly Being Reported by Mac Users

Apple's built-in Time Machine backup solution for macOS appears to be causing problems for some Mac users running the latest versions of Monterey and Big Sur, based on a steady trickle of reports on both the MacRumors Forums and Reddit. While some users are complaining of different issues...

forums.macrumors.com

 

[jz0309]

After upgrading my iMac to Big Sur in the summer I had issues with external drives being used for Time Machine, they basically showed as "bad" in Disk Utility, and, when setting up an external drive in BS for Time Machine it automatically formats it to APFS case sensitive, had multiple posts about it ... the short answer for me was that I am now using CCC for backups, have had no issues and I am super happy with it.

 

[ignatius345]

This was new as of yesterday. My external Time Machine backup drive's disk access light was flashing as accessing all the time. It's a USB 3 portable bus-powered HD. Even after a backup was completed, it was still flashing as accessing the disk even several hours later. I made sure that the Energy Saver Prefs have "Put hard disks to sleep when possible" checked, and yes it was checked. OS is macOS Big Sur 11.6, on a 2017 i5 iMac.

I could access the backups, and I could force a backup and both worked fine. I rebooted and the drive was dormant... until I logged in and then it started accessing again. I again left it for hours and the same behaviour, even when it was not making a backup.

Finally I just deleted the drive and set it up again as a new Time Machine backup, and now it's working normally. As expected, it now goes dormant when not in use, and only gets activated as needed for backups.

What gives? What could cause the drive to be constantly accessed like that, for hours upon hours on end? Could it ever be a sign of drive failure?

---

On another note, my laptop lost the pairing with its Time Machine backup drive connected to an AirPort Extreme. It sees the drive, but wants me to set it up again as a new backup, and does not accept all the old backups on it. I think I'll just nuke that one as well and start over.

Did the Time Machine drive start off APFS formatted or HFS+, when you were first having the problem? I assume that since you reformatted it under Big Sur it's APFS now, but if it was an old HFS+ formatted backup you'd been adding to, that might have been an issue.

Time Machine has changed a ton in Big Sur and Monterey, and is now based on snapshots instead of a massive tangle of symlinks like it used to be when it used HFS+ disk format. Pretty deep dive here, and elsewhere on this site: https://eclecticlight.co/2021/10/07/upgrading-to-big-sur-or-monterey-migrating-time-machine-backups/

 

[EugW]

Did the Time Machine drive start off APFS formatted or HFS+, when you were first having the problem? I assume that since you reformatted it under Big Sur it's APFS now, but if it was an old HFS+ formatted backup you'd been adding to, that might have been an issue.

Time Machine has changed a ton in Big Sur and Monterey, and is now based on snapshots instead of a massive tangle of symlinks like it used to be when it used HFS+ disk format. Pretty deep dive here, and elsewhere on this site: https://eclecticlight.co/2021/10/07/upgrading-to-big-sur-or-monterey-migrating-time-machine-backups/

This was an APFS Time Machine backup, that I had started with Big Sur last year.

BTW, this is an issue with my Monterey laptops, since they backup wirelessly to another drive connected to an AirPort Extreme. That drive remains HFS+, since AirPort Extreme doesn't understand APFS.

 

[ignatius345]

This was an APFS Time Machine backup, that I had started with Big Sur last year.

BTW, this is an issue with my laptops, since they backup wirelessly to my drive connected to an AirPort Extreme. That drive remains HFS+, since AirPort Extreme doesn't understand APFS.

Oh, I missed that part. That does definitely add a wrinkle. I have an AirPort Extreme myself, and played with connecting a Time Machine drive at one point, but wasn't able to get it to work reliably.

 

[EugW]

Yeah, since my laptops aren't primary machines, I was OK doing it wirelessly and they worked fine backing up to that AirPort Extreme HFS+ drive, until last month when they stopped recognizing the drive completely. I reformatted that drive (again to HFS+) and now Time Machine working again.

I didn't trust this setup for my iMac, so I directly connected an external drive instead formatted in AFPS, but that eventually failed (hence this thread), after about a year. DriveDX says the drive is fine, and it's all working fine again after a reformat.

I do have other data backups, but I think I'm going to have to start doing clones again.

Also, I wonder if I should bring out my old unused Synology NAS for additional Time Machine backup targets. If I understand it correctly, I can use APFS in that context, even though the NAS is in ext4. Sparsebundles and all that...