Hi,

Having read
https://github.com/daos-stack/daos/blob/master/doc/storage_model.md
is it the case that all storage nodes must have DCPMM (apache pass)
memory?

I was hoping to install a test installation using a metadata server with
DCPMM memory, and storage nodes with only NVMe drivers (these are not
cascade lake, so no DPCMM). However, I am now unclear whether this will
be possible.

Thanks,
Alastair.

DAOS metadata resides in persistent memory (DCPMM) on the same node as the block storage (NVMe drives). DAOS is an object store, not a file system. The metadata in the DCPMM are the data structures that each DAOS server maintains to access the application data stored in DAOS containers and objects on the SSDs.

--jc

Note that the DCPMM also captures small I/Os (< 4k) in addition to the DAOS metadata.

That being said, for a quick test setup, you can use DRAM instead of DCPMM (use a tmpfs mount).
Again this is just for testing (if you reboot of course all data / metadata in your tmpfs is gone).

Thanks,
Mohamad

On 7/26/19, 8:56 AM, "daos@daos.groups.io on behalf of Carrier, John" <daos@daos.groups.io on behalf of john.carrier@...> wrote:

DAOS metadata resides in persistent memory (DCPMM) on the same node as the block storage (NVMe drives). DAOS is an object store, not a file system. The metadata in the DCPMM are the data structures that each DAOS server maintains to access the application data stored in DAOS containers and objects on the SSDs.

--jc