FlashArray connects to Access Appliance as depicted in Figure 5 and as previously mentioned sends snapshots to the Access Appliance via the NFS protocol. The hosts can connect to FlashArray using fiber channel (16 or 32 Gb), iSCSI or NVMe/RoCE (RDMA over converged Ethernet). For Snap to NFS and CloudSnap, the FlashArray replication ports and bond are utilized, which depending on the FlashArray model are 10 or 25 GbE in active/passive mode. In this mode, only one network interface is active, and the other interface will only become active when the first network interface becomes unavailable. FlashArray can communicate with any of the four 10 GbE network interfaces on the Access Appliance side (two 10 GbE per node). For more bandwidth, the Access Appliance network interface can be bonded if desired.
Figure 5 - Host, FlashArray and Access Appliance Solution Connection Example
SNAP TO NFS
Currently, only one NFS offload target can be configured per FlashArray by specifying the NFS export share, the IP address or hostname of the NFS server and mount options. Once the connection is successfully established, the offload target can be defined within the protection group where volume snapshots can be offloaded or replicated. As previously stated, a protection group is where volume(s) can be specified to be protected using snapshot technology and then offloaded to a replication target. Point-in-time protection group snapshots of these volumes can be created manually or via a schedule on the FlashArray. These snapshots can then be sent or replicated to the Access Appliance either manually or by scheduling for long term retention.
As illustrated in Figure 6, there is a set of volumes defined within a protection group. Snapshots of the volumes belonging to the protection group are taken and stored locally on the FlashArray. The initial snapshot (baseline) sent to the offload target is the full, compressed volume data. For subsequent snapshots, only delta changes are sent to the offload target. This offloading technique results in lower network utilization, reduced space consumption on NFS target and less time to send the snapshot(s).
Figure 6 - Snap to NFS Example Flow
The offloaded FlashArray snapshots are fully portable, self-describing and allow for complete restoration of volume(s) to the source or another FlashArray. The data portions of the snapshots are sharded into files of maximum sizes of 70 MB and several meta-data files of less than 500 bytes. On the Access Appliance, the data and meta-data files of the snapshots are embedded within several directory structures as shown in Figure 7.
Figure 7 - Sample View of Files/Directories Representing the FlashArray Snapshot on Access
SNAPSHOT RETRIEVAL
When restoring, FlashArray can retrieve one or several volumes in the protection group from the Access Appliance. In Figure 8, the compressed data that make up the requested snapshot is requested and then re-assembled onto the FlashArray as a volume snapshot. To reduce network bandwidth, only missing data blocks not already present on the FlashArray are transferred to rebuild the entire snapshot. The volume snapshot can further be restored to a volume with an option to overwrite or make a copy if the volume exists.
Figure 8 - Snapshot Retrieval Flow