[lustre-discuss] How does Lustre client side caching work?

Michael Di Domenico mdidomenico4 at gmail.com
Wed Jul 26 05:02:25 PDT 2017


On Wed, Jul 26, 2017 at 2:19 AM, Dilger, Andreas
<andreas.dilger at intel.com> wrote:
> We have discussed integration of fscache with the Lustre client to allow
> persistent cache on NVMe/Optane/NVRAM or other fast local storage. IMHO,
> there is little benefit to cache on slower local devices (e.g. HDD) since
> Lustre can read over the network (assuming IB and decent servers) at a large
> fraction of the PCI bandwidth. That would only be a win over WAN or other
> slow networks.

i might disagree slightly with this.  i certainly have a use case
where the aggregate performance of the individual cluster nodes
reading from local disk (even using sata) outstrips the aggregate
lustre bandwidth.  the size of our clusters far out strip the
aggregate speed compared to the filesystem.  being able to cache a
file locally and re-read it a number of times would be beneficial in
some of our use cases.  and since we share our filesystems between
multiple clusters, this would also prevent one cluster from hammering
the filesystem making less usable in another


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