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Gateway nodes use the PowerEdge R750 but with a different RAID configuration that has four x16 slots and two x8 available for any other adapter. The four x16 slots have Mellanox ConnectX-6 Single Port VPI adapters, that can be configured for either IB HDR or Ethernet 200 Gb connections or any of the speeds supported by those adapters, at least one of those adapters must be connected to the PixStor storage solution to get access to the file system, two connections if redundancy is required on any single gateway. In addition, the gateways can be connected to other networks adding NICs supported by the PowerEdge R750 on the two x8 slots available (one internal x8 slot is used by a special PERC adapter to manage local SSDs for the OS).
The Samba’s Clustered Trivial DataBase (CTDB) is a clustered database used to manage the NFS and SMB services on the gateway nodes, providing high availability, load balancing and monitoring of the nodes in the CTDB cluster. For each of the gateways in the CTDB cluster, a Domain Name System (DNS) entry with a record for their IP is added, such that all have the same hostname, a sort of “public gateway name.” That gateway name is then used by clients to mount those services, that way the name server daemon (named) can assign all the gateways in the CTDB cluster to clients in a sequential round-robin fashion. When needed, NFS-Ganesha (an open source, user space, NFS file server) can be used as an alternative to the regular NFS server services, and it is also managed by the CTDB cluster.
Behind the gateways, a PixStor system must be accessed and exported to the clients. For characterizing the gateways in this work, a PixStor solution with high-demand metadata and the capacity expansion modules was used.
Since the backend storage remains the same, gateway node performance was not expected to change significatively. Therefore, gateway performance characterization is not included in this document.