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I just tried to set up a Time Machine backup for a MacBook Air using my NAS and, when I did, my original iMac says that I can't back it up because the backup on my NAS is already in use. The backup files have different names but are on the same NAS. Is trying to put Time Machine backups for two different Macs causing this issue and, if so, is there a solution? Thanks.
iMac 21.5″ 4K
There are two important issues which should be identified. First, your backup disk should be large enough to do the job. Ideally it wold be 2 or 3 times as large as the data to be backed up. Second, you should not mix two backups to the same disk. Ideally, each computer should have its own external disk directly connected to it with a USB cable. If you insist on using only one disk, it should be formatted into two sections and each one would have a different name such as Backup A and Backup B. Then each computer would backup to its assigned format section. Remember, eventually all disks will fail, including backup disks. Having two disks increases your data's security.
There are two important issues which should be identified. First, your backup disk should be large enough to do the job. Ideally it wold be 2 or 3 times as large as the data to be backed up. Second, you should not mix two backups to the same disk. Ideally, each computer should have its own external disk directly connected to it with a USB cable. If you insist on using only one disk, it should be formatted into two sections and each one would have a different name such as Backup A and Backup B. Then each computer would backup to its assigned format section. Remember, eventually all disks will fail, including backup disks. Having two disks increases your data's security.
Thanks, HWTech! I just created two new share folders on my Synology NAS, one for my iMac and one for my MacBook. But my existing Time Machine backups on in a third, different share folder on my NAS. How do I migrate those and future backups to the new share folders? When I tried to add a backup disk for my iMac, it said there were "no available Time Machine destinations." Do I need to delete the old destination first? Many thanks.
Sorry, I don't know since I don't use TM....besides TM backups stored on a NAS may be a bit different than a TM backup stored on a locally connected external drive. From reading these forums, it doesn't appear like you can copy a TM local backup drive, but I believe it may be possible for a TM backup on a NAS.
I wouldn't touch your current backups. Did the new share work for you Macbook? I would say experiment with the Macbook by creating yet another new share to experiment test things out before trying to modify the iMac's backups. This includes trying to have two TM backups on two separate shares and also trying to move an existing backup to another share.
I would think if you added a new share, then you should be able to add it as a second backup destination, but then I don't know how TM handles backups to networked locations (it is possible to add a second local TM backup drive to have two TM backup drives).
Hopefully another contributor with more knowledge of TM and TM backups to a NAS will chime in here.
You may want to consider having two separate shares on your NAS...one dedicated to each Mac for their TM backup. This way they would be separated.
Using one NAS for Time Machine Backups on Two Different Macs
