USAFRet :
With a 2 drive box, you only get the choice of RAID 0 (striped) or RAID 1 (mirrored).
Both mostly useless in a home environment.
Synology also supports JBOD mode, so adding a second drive will increase capacity.
https://www.synology.com/en-us/knowledgebase/DSM/help/DSM/StorageManager/volume_diskgroup_what_is_raid
https://www.synology.com/en-us/knowledgebase/DSM/help/DSM/StorageManager/volume_diskgroup_expand_add_disk
You'll still lose data on the entire JBOD volume if a drive dies, just as with RAID 0. (Or more accurately, you'll lose the data on the dead drive. The data on the other drive could still be recovered if you wanted, it just wouldn't work as part of the JBOD volume anymore.) But this risk is rendered moot if he keeps backups. I assume he has other plans for backups, and the point of the NAS is always-on network-accessible storage.
If you
haven't made plans for backups, do so. Having a NAS or RAID doesn't eliminate the need for a backup. Even if you call the NAS a backup because the original data also exists on other computers, the fact that it's always online and available makes it not-a-backup. If some ransomware got onto one of your computers, it could encrypt the "backed up" files on the NAS just as easily as it could encrypt the original files on the infected computer. And you would be SOL.
So ideally the backup should be offline (e.g. unplugged external drive) and off-site (on the cloud, or store the drive at work except the one day a month you backup). As photos tend to be the most valuable pieces of personal digital data, I will mention that:
■If you have a Gmail acocunt, Google Photos gives you free unlimited storage of photos downsized to 2048x2048 or smaller. You also get a free 15 GB allowance with Google Drive which can be used to store higher resolution versions of particularly important photos.
■If you subscribe to Amazon Prime, Prime Photos gives you free unlimited storage of photos of any size.
■If you subscribe to Office 365, it includes 1 TB of storage on Microsoft OneDrive which you can use for cloud backup.
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