Yes and No.
I use both Raid5 & Raid10 configurations all should be backed up.
As stated above Raid5 should be backed up and can fail in a number of ways. If you have 1 drive and only 1 drive fail in the Raid5 you can put a new drive and in most cases the Raid will rebuild. BUT if your drives are old you can have a catastrophic failure. The other drives may not be up to the task of working that long or as hard as required to rebuild the Raid and if any more drives fail while it is rebuilding, say by to all data. The older the drives are the more likely that this could happen.
RAID 10/5 works by striping and mirroring your data across at least 4 drives and is the same as Mirroring, or RAID 1, means writing your data to 2 or more disks at the same time. Even if one disk fails completely, the mirror preserves the information. The chances of a drive failing in both is minimal but is still possible. This also reduces useable space by half plus some. 24TB = !!Tb. As said this is still not fool proof.
Make sure you have a UPS as a sudden loss of power can destroy all data and or may require your Raid to be verified and that can take days.
All this said you can buy WD 6tb My book for under $200, so backup your data. Most in this hobby have cables that cost more than $200.