Synology SHR with mixed drive sizes to mirror data?

[Enquiries]

You have the greatest site - even far better than Synology. Thank you so much for being here!

I have a DS918+ . It will be used to backup (nightly) my data from my windows computers on to the NAS for backup protection. Nothing more. I am having difficulty understanding how my data will write over all 4 drives to MIRROR my data when my drive sizes are not the same. In reality do I now have only 1TB of space to store data in a mirrored fashion? The data storage is not as much my worry as is drive failure. If you can help explain how much of my data is written on to each of those 4 drives and then explain what would happen to the data on each of those drives if a drive (or 2) failed. I hope I am wording this correctly because my confusion makes it even harder for me to explain! Thank you again - you provide an amazing level of information!

[ed]

If you chose SHR1 (RAID1) or SHR2 (RAID6) all data will be equally written across all drives. If one drive fails, you need to replace it before another fails. With SHR1 you can afford one drive failed, the second fail will destroy your data, so replace ASAP. With SHR2 two drives can fail at the same time.I hope this helps.