In HP-UX 11iv3 HP has architected a new mass storage stack and subsystems to significantly enhance scalability, performance, availability, manageability and serviceability. Maximum configuration limits have been increased to address very large SAN configurations while delivering performance with automatic load balancing, parallel I/O scan, optimized I/O forwarding and CPU locality.

 

To enhance availability, the mass storage stack monitors paths to devices, reroutes traffic and recovers from path failures when they occur. The stack has a built-intelligent retry algorithm on path failures and also implements path authentication to avoid data corruption. The introduction of native multi-pathing and path-independent persistent Device Special Files (DSFs) and the auto discovery of devices greatly enhance the overall manageability. New commands and libraries further enhance the manageability and serviceability of mass storage devices.

 

This re-architecture introduces a new representation of mass storage hardware and subsystems called the agile view. The central idea of the agile view is that disk and tape devices are identified via their World Wide Identifier (WWID) and not by a path to the device. Therefore, in the agile representation, multiple paths to a single device can be transparently treated as a single virtualized path, with I/O distributed across many paths. A persistent DSF is not affected by changes in the paths to the device. To take full advantage of this agile view, HP recommends the migration to persistent DSFs.

 

The legacy DSF format for disks is:

Example: /dev/dsk/c5t0d1 or /dev/rdsk/c6t0d1s2

 

The persistent DSF format for disks introduced with the agile view in HP-UX 11i v3 is:

Example: /dev/disk/disk2, /dev/rdisk/disk5_p2

 

By default in HP-UX 11i v3 ioscan shows the legacy view. This view is compatible with previous releases of HP-UX. To enable the agile view in output of the ioscan command you must use the new -N option.

 

In HP-UX 11iv3, the ioscan command offers two new options to map configuration information from the legacy view to agile view:

-m dsf [dsf_name] To map legacy DSFs to persistent DSFs

-m hwpath [-H hw_path] To map legacy hardware paths to lunpath hardware paths and LUN hardware paths

 

The "ioscan -m dsf [dsf_name]" command shows the mapping between character legacy DSFs and character persistent DSFs if no dsf_name is specified. As a rule, the block DSFs are mapped similarly. If a dsf_name is specified, it shows the mapping for this DSF name only.

 

Sample"ioscan -m dsf" output:

 

In the example above the persistent DSF /dev/rdisk/disk17 maps to the legacy DSF /dev/rdsk/c9t0d0. The persistent DSF /dev/rdisk/disk37 maps to the legacy DSFs /dev/rdsk/c5t0d0 and /dev/rdsk/c8t0d0. This also implies that block persistent DSF /dev/disk/disk17 (not shown) maps to block legacy DSF /dev/dsk/c9t0d0.

 

The "ioscan-m hwpath [-H hw_path]" command shows the mapping between legacy hardware paths,lunpath hardware paths, and LUN hardware paths. If a hw_path is specified with option -H, it shows the mapping for that hw_path only.

 

Sample "ioscan -m hwpath" output:

 

The Legacy H/W path is the hardware path for the legacy DSF. The Lun H/W path is the virtualized hardware path representing the LUN. The Lunpath H/W Path is the physical hardware path to the LUN. The LUN under Lun H/W Path 64000/0xfa00/0x1a shows that it has two lunpaths leading to it. Note that the last two elements of a LUN H/W path and a Lunpath H/W path use the hexadecimal notation instead of the decimal notation.