Yes it is a system design. Backblaze's main reliability system is erasure coding[4] of shards of files, which is not RAID[1][2]. RAID mirrors disks or volumes

Yes it is a system design. Backblaze's main reliability system is erasure coding[4] of shards of files, which is not RAID[1][2]. RAID mirrors disks or volumes on block or filesystem layers, not files in userspace. That being said, I stand corrected in that they did use RAID at some point in time[3] (RAID6 on 13+2 drives), and may still be using some form of RAID. OTOH their reliability calculations don't seem to consider RAID - calculating with individual drive failures and shard rebuilds. [1] https://en.wikipedia.org/wiki/RAID https://en.wikipedia.org/wiki/RAID [2] https://en.wikipedia.org/wiki/Non-RAID_drive_architectures https://en.wikipedia.org/wiki/Non-RAID_drive_architectures [3] https://www.backblaze.com/b2/storage-pod.html https://www.backblaze.com/b2/storage-pod.html [4] https://www.backblaze.com/blog/cloud-storage-durability/ https://www.backblaze.com/blog/cloud-storage-durability/