[lustre-discuss] Lustre and Optane
adilger at whamcloud.com
Mon Jan 13 11:56:42 PST 2020
The most likely candidate for effectively using Optane/NVRAM would be
via Persistent Client Cache (PCC), which allows client-local storage to
be part of the Lustre namespace. Files can be cached on a local NVRAM
device (managed by a local filesystem like ext4, or possibly something
more experimental like NOVA for better performance) and then migrated
into the cache.
Once the file is in PCC, it can be accessed via the local filesystem
operations, including DAX, for very low-latency operations. See the
presentation from LAD'19 for details:
It should be noted that in Lustre 2.13, files in PCC are NOT resident in the
main filesystem, so if the client node goes offline then the files will not be
accessible until the client node is restarted. For some workloads this is OK
(e.g. files being generated locally with high IOPS that are occasionally
needed on other clients), but not for others. We will be improving PCC to
use FLR to mirror a copy into the client cache and still keep a copy in the
main filesystem, but that is not available yet.
On Jan 13, 2020, at 10:03, Dave Holland <dh3 at sanger.ac.uk<mailto:dh3 at sanger.ac.uk>> wrote:
I haven't been to LUG or LAD recently, so I'm a bit out of the loop, but
how much use is Optane finding in the Lustre world?
The main obstacle I see is that it's server-local, so building a
resilient/failover-capable system isn't straightforward.
Thanks for any observations.
** Dave Holland ** Systems Support -- Informatics Systems Group **
** 01223 496923 ** Wellcome Sanger Institute, Hinxton, UK **
Principal Lustre Architect
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