Pre-Installation Considerations

Lists the recommendations that you must follow before installing MAST Gateways.

By default, the MAST Gateway uses 16 threads for volume and file offload and recall operations and another 16 threads for handling internal operations and other operations such as reads (which triggers automatic recall requests), writes, etc. Each thread processes offload or recall of a container (associated with a volume). Each MAST Gateway can process one or more volumes (and associated containers) simultaneously depending on the number of threads available for processing the containers associated with the volumes. Each volume is assigned to a MAST Gateway for a tiering operation irrespective of the number of containers associated with the volume.

For example, suppose you have a volume with 5 containers. The MAST Gateway allocates 5 threads, one per container, to process the offload of that volume’s data; the other 11 threads are available for other tiering-related operations on other tiering-enabled volumes. However, if you have a volume with 20 containers. The MAST Gateway allocates all 16 threads to process the offload of that volume’s data and as threads are freed, other unprocessed containers associated with the volume are processed. Now, suppose that you have configured multiple MAST Gateways for the volume that has 20 containers. . Volume offload is then distributed among the multiple MAST gateways, leading to enhanced performance of the cluster. If you have multiple large volumes with multiple containers, MapR recommends more than one MAST Gateway to process all the containers associated with all the volumes.

If you have a limited number of nodes that can access the cold tier (because of controlled access to WAN, proxy setup, etc.), install and run MAST Gateway on only those nodes and set up proxy server parameters in the mastgateway.conf file. See step 5 in Configuring the MAST Gateway Service for more information on the configuration parameters to set for using a proxy server. On the other hand, if all the cluster nodes can access the tier, then consider the following before deploying the MAST Gateway:

  1. A single MAST Gateway can offload at around 300 MB/sec at full throttle. So, compute the minimum number of MAST Gateways based on network capacity of the connection to the tier.
  2. If you expect many volume offloads and recall operations to get triggered at the same time, consider installing MAST Gateways on a few more nodes or adding more MAST Gateways at a later time. See Installing the MAST Gateway for information.

In general, you must allocate at least 2GB of memory for the MAST Gateway operations. The memory consumption can increase during heavy load. See settings for configuring memory for MAST Gateway in Step 7 for Configuring the MAST Gateway Service.

NOTE
Before installing MAST Gateways, you must ensure that the system time on all the cluster nodes is the same. If the system time on CLDB and file server nodes are different, the mtime rule for migrating data might not work as intended. If you see a time skew alarm in the cluster, resolve the alarm immediately to prevent catastrophic failures.