I have a NAS containing RAID5 array (5.4TB in total, 2.9TB in use) using mdadm. Now I plan to modify some hardware of it (especially SATA controller), so I'd like to have a whole backup of this RAID5 filesystem to the external HDD before modification.
As this FS has sooooo many small files and directories, I expect normal rsync or cp would be so slow and end up with out-of-memory error.
So the question is: is there some good ways to make a backup of this kind of things? I'd like to have a mountable backup (files can be accessed when mounted on external HDD) but if it's not possible, I can stand with that.
System details:
[NAS] CentOS 7 (3.10.0-1160.11.1.el7.x86_64) [Filesystem] xfs
[External HDD] Capacity: 4TB
Thanks.