MP All Models Time Machine on infrequently mounted internal volume?

[14UG]

Possibly this belongs in another forum but I thought the MPers might be best placed to answer...

My system drive is on a PCIe NVMe and I have a scratch drive on an SSD RAID 0 on a sonnet PCIe card. The internal slots have an a;ternative system drive (used for working from home) and a 2TB spinning RAID 1 array.

The alternative system drive and the spinning RAID 1 don't mount on boot as I've edited vifs to prevent that. I don't use Innie.kext (yet).

Time Machine is set to back up the system drive (NVMe) and the RAID 1 only. If Time Machine backs up without the RAID 1 mounted (this happens all the time) the next time the RAID 1 is mounted it needs to back-up from scratch.

Here's my question (finally!)... Is there a way I can prevent an infrequently mounted volume from backing up from scratch each time?

Thanks to anyone who has bothered to read and understand the above!

 

[MarkC426]

Why not have it mount on boot, is this to save electricity.....?
If it is not used regularly it will spin down as per energy saving settings.

TM should only back up anything new and maybe a snapshot.
I think if a drive is omitted from backup and then added it does a full backup, this is then repeated if that drive is re-added (treated as a new addition).

 

[Soba]

Time Machine is set to back up the system drive (NVMe) and the RAID 0 only. If Time Machine backs up without the RAID 0 mounted (this happens all the time) the next time the RAID 0 is mounted it needs to back-up from scratch.

This should not be the case. Are you sure it is actually backing up everything each time, or is it simply running a full scan and then backing up only the changed files? Are you seeing something in the Time Machine UI that makes you think it's doing a full backup every time?

 

[14UG]

This should not be the case. Are you sure it is actually backing up everything each time, or is it simply running a full scan and then backing up only the changed files? Are you seeing something in the Time Machine UI that makes you think it's doing a full backup every time?

Thanks. Well I did a bunch of major upgrades to my MacPro (new OS, CPU tray, RAM, SMC battery, system drive you name it). The new system drive was prompted to adopt the old backup which I accepted. The initial backup was approx 1.5TB (the size of my spinning RAID 1). I thought at that point that it just needed to refresh what was a very old back up.

but the next time my spinners were mounted it said it needed to do another 1.5TB back up?

that’s what makes me think that it is somehow resetting each time it back ups with only certain drives mounting.

maybe I need to give it more time though.

I ran Applejack at some point during the upgrades (can’t actually remember when/why) and it found some corrupt Time Machine prefs which it claimed it repaired.

 

[Soba]

Thanks. Well I did a bunch of major upgrades to my MacPro (new OS, CPU tray, RAM, SMC battery, system drive you name it). The new system drive was prompted to adopt the old backup which I accepted. The initial backup was approx 1.5TB (the size of my spinning RAID 1). I thought at that point that it just needed to refresh what was a very old back up.

but the next time my spinners were mounted it said it needed to do another 1.5TB back up?

that’s what makes me think that it is somehow resetting each time it back ups with only certain drives mounting.

maybe I need to give it more time though.

I ran Applejack at some point during the upgrades (can’t actually remember when/why) and it found some corrupt Time Machine prefs which it claimed it repaired.

Understood. A few thoughts:

According to (the late, great) James Pond, Time Machine will sometimes do a full backup on a volume if it's been unmounted for many days and there are many changes to the files. (Note the last bullet point here: http://oldtoad.net/pondini.org/TM/D3.html ) About how often do you mount the RAID volume?

I am curious about what you have on the RAID volume and how the contents might be changed. Are you storing large virtual machines (such as for VMWare Fusion) or similar? If the files are very large and are changed even the slightest bit, the entire file will be backed up again. (I believe this is no longer the case in Big Sur.)

I suggest trying the Time Tracker utility to find out exactly what's being backed up every time. This will help you figure out if everything on your RAID volume is being backed up or only a large portion of it, and from there you can start figuring out if those files are actually changing or if Time Machine is the source of the problem. (Time Tracker is linked from here: http://oldtoad.net/pondini.org/TM/A2.html )

If none of this ends up helping, you can try a full reset of Time Machine. The procedure for doing that is here: http://oldtoad.net/pondini.org/TM/A4.html

Let us know what you find out.

 

[mattspace]

FYI most of the stuff you do with Pond's instructions (and also your setting a volume not to mount at boot) can be done with Tinkertool System, which is reasonably priced, and gives you a nice graphical front end to all the Time Machine tools (and masses of other stuff) that otherwise require TMUtil from the command line.