It's a shame that Linux doesn't have APIs as comprehensive as Windows VSS. One of the several features is something called Volume Shadow Copy Service which lets you take backups of block devices which are in use. It's kind of similar to this but more supported and I think it also interacts with user processes like databases, quiescing them so you can take a consistent snapshot.
[Also if you are playing with custom block devices in Linux -- mounted or otherwise but not /dev/sda -- https://gitlab.com/nbdkit/nbdkit https://libguestfs.org/nbdkit.1.html One filter we have which is kind of similar to blktrace is called the nbdkit-stats-filter https://libguestfs.org/nbdkit-stats-filter.1.html]