TimeMachine, multiple Macs backing up to the same NAS

[VitoBotta]

I bought an AsuStor NAS some months ago and configured 3 Macs to back up to it, using the same shared folder for simplicity at the time. However the shared folder is almost full now. I haven't seen any errors from TimeMachine or anything like that, but I have the impression that backups have become much slower.

Should I reformat and create 3 separate folders, one for each computer? Does it matter? Can the fact that the three Macs are backing up to the same folder cause data loss/corruption? Thanks

 

[kitKAC]

When Time Machine backs up to a network location sparsebundles are used (all the files are stored in what looks like one single file). If the shared location is almost full then Time Machine is most likely trimming the older backups from the sparsebundle to make room for new files, and that's what's causing the slowdown.

You can install The Time Machine Mechanic (T2M2) and see if this is the case while Time Machine is running.

https://eclecticlight.co/consolation-t2m2-and-log-utilities/

 

[VitoBotta]

When Time Machine backs up to a network location sparsebundles are used (all the files are stored in what looks like one single file). If the shared location is almost full then Time Machine is most likely trimming the older backups from the sparsebundle to make room for new files, and that's what's causing the slowdown.

You can install The Time Machine Mechanic (T2M2) and see if this is the case while Time Machine is running.

https://eclecticlight.co/consolation-t2m2-and-log-utilities/

I think I will format and start from scratch if that can help restore backup speed. Will check out that utility, thanks!

 

[Bigwaff]

I bought an AsuStor NAS some months ago and configured 3 Macs to back up to it, using the same shared folder for simplicity at the time. However the shared folder is almost full now.

Using the AsuStor admin panel, you should be able to expand the shared folder's capacity.

 

[VitoBotta]

Using the AsuStor admin panel, you should be able to expand the shared folder's capacity.

My model is on the cheap side and doesn't allow you to set a quota for each folder. But TimeMachine now does! I reformatted the NAS and reconfigured TimeMachine on the three Macs and it allowed me to configure quotas for each of them. They are all doing the first backup now and the NAS is working at Gigabit speed as expected.

 

[HobeSoundDarryl]

The "re-format and start from scratch" will only lead to the same destination UNLESS you allocate capped space to each of the 3 Macs for TM backups.

And no matter what storage you allocate, it will eventually "fill up." TM is designed to preserve your ability to go "back in time" by hanging on to progressively older versions of files UNTIL the storage space is nearly full... at which time, it will begin deleting the oldest versions that are backed up to create space for new backups. From then on, it's a rolling backup.

The analogy would be to imagine an actual time machine that can only go back so many weeks. For the sake of this example, let's imagine that is 10 weeks. If you used it today, you could travel back to exactly 10 weeks ago. However, wait a week before you use it and you could only go back 9 weeks from today. Wait another week and you could only go back 8 weeks from today. etc. The 10 weeks "rolls" forward with the passage of time.

Apple TM is not really working with time but file versions. But the idea is mostly the same: hang on to older and older versions of backed-up files until it runs out of new space for newest backups. Then it starts deleting its file versions before "10 weeks" (per the example just shared) to create space for the new "week" to be backed up today. Again, this is actually file versions instead of time, but I'm guessing the time concept is easier to grasp.

The issue with simply sharing one block of space for 3 Macs is that they won't actually divvy up the space between them... such as a concept of automatically sharing it as a third of the space for each Mac. Instead, the Mac able to backup the most frequent- like a desktop- will likely eventually hog up nearly ALL of the space. MBs not being there to back up as frequently will- when connected again- find their space for backups smaller than the Mac(s) pretty much always connected.

So if you wanted to give each of them roughly equal space (or some percentage of space you desire for each), you'll need to allocate specific space for each of them with partitioning or tools associated with the NAS that lets you cap a size in a total pool of storage for TM backup space.

 

[VitoBotta]

The "re-format and start from scratch" will only lead to the same destination UNLESS you allocate capped space to each of the 3 Macs for TM backups.

And no matter what storage you allocate, it will eventually "fill up." TM is designed to preserve your ability to go "back in time" by hanging on to progressively older versions of files UNTIL the storage space is nearly full... at which time, it will begin deleting the oldest versions that are backed up to create space for new backups. From then on, it's a rolling backup.

The analogy would be to imagine an actual time machine that can only go back so many weeks. For the sake of this example, let's imagine that is 10 weeks. If you used it today, you could travel back to exactly 10 weeks ago. However, wait a week before you use it and you could only go back 9 weeks from today. Wait another week and you could only go back 8 weeks from today. etc. The 10 weeks "rolls" forward with the passage of time.

Apple TM is not really working with time but file versions. But the idea is mostly the same: hang on to older and older versions of backed-up files until it runs out of new space for newest backups. Then it starts deleting it's time before "10 weeks" (per the example just shared) to create space for the new "week."

The issue with simply sharing one block of space for 3 Macs is that they won't actually divvy up the space between them... such as a concept of automatically sharing it as a third of the space for each Mac. Instead, the Mac able to backup the most frequent- like a desktop- will likely eventually hog up nearly ALL of the space. MBs not being there to back up as frequently will- when connected again- find their space for backups smaller than the Mac(s) pretty much always connected.

So if you wanted to give each of them roughly equal space (or some amount of spaces you desire for each), you'll need to allocate specific space for each of them.

I assigned quotas with TimeMachine, and the sum of the quotas is such to leave some free buffer on the NAS.

 

[HobeSoundDarryl]

I thought I knew a LOT about TM but I'm not aware of a way to assign TM backup size or quotas with TM. I know how to do that with partitions or volumes and/or within some NAS device, TM-supporting software... but was not aware of a way to do that within TM itself. Perhaps a new feature has been released to make this possible since I last dug into the details of TM? Or maybe something one can do in Terminal?

Update: I do see this using a Terminal command... and within the comments of that thread, apparently Sonoma does allow it to be set in the GUI when setting it up. However, a comment says that once set, it can't change without recreating the full backup. If me, I'd be tempted to accomplish the same with partitions or volume allocations and retain the ability to fatten the storage as I might add more physical drive space to a NAS over time.

But it's always nice to have options... and that is a good, simple one for multi-Mac households.

 

[VitoBotta]

I thought I knew a LOT about TM but I'm not aware of a way to assign TM backup size or quotas with TM. I know how to do that with partitions or volumes and/or within some NAS device, TM-supporting software... but was not aware of a way to do that within TM itself. Perhaps a new feature has been released to make this possible since I last dug into the details of TM? Or maybe something one can do in Terminal?

Update: I do see this using a Terminal command... and within the comments of that thread, apparently Sonoma does allow it to be set in the GUI when setting it up. However, a comment says that once set, it can't change without recreating the full backup. If me, I'd be tempted to accomplish the same with partitions or volume allocations and retain the ability to fatten the storage as I might add more physical drive space to a NAS over time.

But it's always nice to have options... and that is a good, simple one for multi-Mac households.

I didn't need any terminal commands. When you select a drive for TM it allows you to set the quota with a slider.

See the quota info in this picture