SAS multipathing

CloudByte ElastiStor supports SAS multipathing. Having multiple physical paths to the disk array enclosure assures effective path failover by providing redundant paths for data access.

  • By default, SAS multipathing is enabled.
  • SAS multipathing is an active/passive setup
  • At any point in time, there is only one active path for I/O
  • If a failure occurs, instead of the active path, the one that was redundant (so far) takes over avoiding any interruption to data access

Prerequisites

  • Two LSI SAS616X switches
  • LSI SAS2008 HBA (at the Node side)
    • Firmware: 07.15.08.00
    • Driver: 15.00.00.00
  • SAS cables
  • Disk array enclosure with multiple IN ports (for example Dell MD1220)
  • Nodes (for example Dell R720)
  • In the Add Node page, clear all existing pools before you import an array enclosure previously connected to a different ElastiStor setup (for instance, an older version). To do this, In the Nodes page, select the Node and then at the bottom of the page, click Clear for all Pools in the table Existing Pools.

Sample setup

The following figure shows a simple SAS multipath setup:

sas_multipath

 

Verifying the setup in ElastiCenter

When you have the multipath set up, the paths are visible in the related Node page.

  1. In CloudByte ElastiCenter, click Nodes.
  2. In the Nodes page, select the Node and then click Storage. The Disk Table provides the details as highlighted in the following figure:

sas_multipath_config

In the case of a failure, as shown in the following instance the path disappears from the table:

sas_multipath_config_fail

 

The figure implies that there is only a single SAS path available.