As macOS user and beginner in the Raspi/OMV-environment I was asking myself: "How can I perform a quick and easy doing backup and restore of my sd-card within macOS?". All howtos, manuals, guides, ... I found so far were based on Windows and/or Linux environments.
At the end I've got a hint from a colleague to have a look at "Apple Pi Baker".
I successfully tested it several times now backing up the sd-cards of my OMV-Raspi and Homebridge/piHole-Raspi as well as restoring the backups to new sd-cards within minutes and a few mouseclicks. It was possible also to restore a backup created from my 32GB-sd-card to a 160GB-sata-Harddrive in a sata/usb-enclosure and boot my Raspi from this without any problems.
With Apple Pi Baker it is possible with a few mouseclicks to perform an offline-backup of my 32GB-SanDisk-Extreme-sd-card containing around 6GB of data (OMV + Plex) within 8 minutes on my MacBook Pro 14" without any manual intervention. At end I've got a 4,5GB backup.zip file.
In the background Apple Pi Baker is doing a block-copy of your sd-card, shrinking and compression afterwards (restore the other way round: uncompress, enhance, copy).
On the linked website of this tool there's a very good documentation of all functions, restrictions and usage.
Maybe this information helps the one or other beginner in Raspi/OMV/Linux using macOS.
Btw.: maybe this sounds like marketing blabla, but I'm really just a satisfied user of this SW and won't get paid on this article 
