[lustre-devel] RFC: Spill device for Lustre OSD

[Day, Timothy]

> >I haven’t seen any mention of failover yet in this conversation (may have missed it), but if the device is truly local, then in failed over configurations the data is inaccessible.  If it’s *not* local, why not just make the device part of the OST or an independent OST?
>
> It won't be local. Actually, this is designed for the cloud.

I don't understand how 'local' is being used. Cloud or not, all of the Lustre client,
servers, and backend storage service will be co-located in the same data center. I
think Patrick is asking whether the spill device will be physically connected to OSS
server, or be provided over something like SAN? Either way, presenting this
device as an independent OST brings back the pain of manually
managing data placement from the client - which this design is trying to avoid.

> We already have tiered storage based on mirroring; however, that still requires clients to move data and a file system level scanner to decide which files move to the cold tier. It's cumbersome to maintain those clients.

Agree, it's not ideal.