HP MSA1000 is an entry-level disk storage capable of communicating via different types of interfaces, such as SCSI and FC, and can allow FC failover. This FC failover, however, is controller failover and not path failover. It means that if the primary controller fails entirely, the backup controller will “kick in”. However, if a multi-path capable client will fail its primary interface, there is no guarantee that communication with the disks through the backup controller.
The symptom I have encountered was that the secondary path, while exposing the disks (while the primary path was down for one of the servers) to the server, did not allow any SCSI I/O operations. This prevented the Linux server’s SCSI layer from accessing the disks. So they did appear when doing “cat /proc/scsi/scsi“, however, they were not detected using, for example, “fdisk -l“, and the system logs got filled with “SCSI Error” messages.
About a month ago, after almost two years, a new firmware update has been released (can be found here). Two versions exist – Active/Passive and Active/Active.
I have upgraded the MSA1000 storage device.
After installing the Active/Active firmware upgrade (Notice Linux users – You must have X to run the “msa1500flash” utility), and after power cycling the MSA1000 device, things start to look good.
I have tested performance with a person on-site disconnecting fiber connections on-demand, and it worked great. About 2-5 seconds failover time.
Since this system run Oracle RAC, and it uses OCFS2, I had to update the failed-node timeout to be 31 seconds (per this Oracle’s OCFS site, which includes some really good tips).
So real High Availability can be archived after upgrading MSA1000 firmware.