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| Mainframe Appliance for Storage |
MAS Disk Drive NamesThe Mainframe Appliance for Storage (MAS) supports disk drives attached to the internal SCSI adapter (the six front-access drives), to the external SCSI port, and via the fibre-channel adapter(s). All of these appear to Linux as SCSI drives. Linux gives SCSI drives the device names /dev/sdx, where x is 'a' for the first drive, 'b' for the second drive, 'c' for the third drive, etc. All of the drives are discovered and (re-)named each time Linux boots. (Unfortunately) Linux has no memory of drive name assignments from prior boot cycles; the drives are re-discovered and renamed each time the system restarts. Because existing drive names will change when other drives are added or removed, it is highly recommended that you don't refer to drives by name on a regular basis, such as in mount commands, but instead use "labels" on a disk filesystems. For more information on this subject, refer to the MAS Users Guide. Please Note: Disk drive naming methodolgy changed between MAS releases 2.xx and 3.xx. Please refer to the proper section below to understand disk drive naming for your release of MAS. Name Assignments (MAS Release 2.xx) In MAS Release 2.xx, Linux assigns names to the disk drives it finds in the following sequence: 1. Drives in the internal drive bays are named first, starting at /dev/sda. The names are assigned in SCSI ID sequence, which happens to match the physical layout of the bays starting at the upper left bay and proceeding top to bottom, followed by the right bays, top to bottom. Empty bays are skipped, and don't affect drive names at all. 2. Drives on the external SCSI bus are named next, starting at the next available /dev/sdx name. They are assigned names in their SCSI ID sequence. 3. Drives attached to the fibre-channel adapter(s) are assigned the next available names, starting on the first fibre-channel adapter and then proceeding to the second adapter. If any drive is attached to both fibre-channel adapters, it does not get assigned a new name on the second adapter. It transparently gets dual-path support on the name assigned on the first adapter. Example 1: Internal drives in bays 1 and 2 (master system disks), internal drive in bay 3 (data disk). Drive names would be:
Example 2: Internal drives in bays 1 and 2 (master system disks), external SCSI drive:
Example 3: Internal drives in bays 1 and 2 (master system disks), external SCSI drive, external fibre-channel drive (SCSI ID 1) attached to both fibre-channel adapters, and external fibre-channel drive (SCSI ID 2) attached to fibre-channel adapter 2 only:
Name Assignments (MAS Release 3.xx) In MAS Release 3.xx, Linux assigns names to the disk drives it finds in the following sequence: 1. Drives on the external SCSI bus are named first, with the first being /dev/sda, the second /dev/sdb, and so on. The names are assigned in their SCSI ID sequence, lowest to highest. 2. Drives in the internal drive bays are named next, starting at the next available /dev/sdx name. They are named in SCSI ID sequence, which happens to match the physical layout of the bays starting at the upper left bay and proceeding top to bottom, followed by the right bays, top to bottom. Empty bays are skipped and don't affect drive names at all. 3. Drives attached to the fibre-channel adapter(s) are assigned the next available names, starting on the first fibre-channel adapter and then proceeding to the second adapter. If any drive is attached to both fibre-channel adapters, it does not get assigned a new name on the second adapter. It transparently gets dual-path support on the name assigned on the first adapter. Example 1: Internal drives in bays 1 and 2 (master system disks), internal drive in bay 3 (data disk). Drive names would be:
Example 2: Internal drives in bays 1 and 2 (master system disks), external SCSI drive:
Example 3: Internal drives in bays 1 and 2 (master system disks), two external SCSI drives (SCSI IDs 2 and 5), external fibre-channel drive (SCSI ID 1) attached to both fibre-channel adapters, and external fibre-channel drive (SCSI ID 2) attached to fibre-channel adapter 2 only:
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