They do not use RAID. They use userspace erasure coding of data stored in files ...

jandrese · on April 15, 2020

It's software RAID. RAID isn't a piece of hardware, it's a system design.

labawi · on April 15, 2020

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

[2] https://en.wikipedia.org/wiki/Non-RAID_drive_architectures

[3] https://www.backblaze.com/b2/storage-pod.html

[4] https://www.backblaze.com/blog/cloud-storage-durability/