Re: [LSF/MM TOPIC] Software RAID Support for NV-DIMM

Dan Williams
2019-02-15T16:34:36Z

On Fri, Feb 15, 2019 at 1:57 AM Johannes Thumshirn <jthumshirn@suse.de> wrote:
>
> (This is a joint proposal with Hannes Reinecke)
>
> Servers with NV-DIMM are slowly emerging in data centers but one key feature
> for reliability of these systems hasn't been addressed up to now, data
> redundancy.
>
> While it would be best to solve this issue in the memory controller of the CPU
> itself, I don't see this coming in the next few years. This puts us as the OS
> in the burden to create the redundant copies of data for the users.
>
> If we leave of the DAX support Linux' software RAID implementations (MD,
> device-mapper and BTRFS RAID) do already work on top of pmem devices, but they
> are incompatible with DAX.
>
> In this session Hannes and I would like to discuss eventual ways how we as an
> operating system can mitigate these issues for our users.

One feature request I have heard in this space is to at least have
filesystem metadata redundancy for DAX. For applications that can
handle their own data-replication the single-point-of-failure FS
metadata becomes a larger liability.