Overview: The Next Generation Mass Storage Stack (September 2009)
Table Of Contents
- Abstract
- Background
- Features of the Next Generation Mass Storage Stack
- Impact
- Background
- Impact
- Background
- Impact
- Background
- Impact
- Impact
- Introduction to the Agile View
- Changes to I/O and Mass Storage Subsystems
- Changes to Other Subsystems
- Migrating to the Agile View
- Conclusion
- Glossary
- Appendix A: Summary of Changes
- Appendix B: Using ioscan
- Appendix C: Using scsimgr
- Appendix D: Interpreting Lunpath Hardware Paths
- For more information
Performance • Improved I/O bandwidth through native multi-pathing with choice of load balancing
algorithms
• Faster I/O scan time through parallelized scanning of mass storage devices
• Faster dump time by writing concurrently to multiple dump devices
Backward Compatibility
HP-UX 11i v3 provides full backward compatibility when using legacy mode, except in very limited cases. Legacy
DSFs remain on the system and continue to work as before, unless you explicitly disable legacy mode. All
commands execute in legacy mode by default, meaning that their behavior is unchanged from previous releases if
you use legacy options and input parameters. All legacy ioctls and APIs are supported in legacy mode on HP-UX
11i v3.
The exceptions to full backward compatibility are:
• The setboot command displays information in the agile view only, as described in Changes to Other
Subsystems: setboot(1M).
• Cold-installing HP-UX 11i v3 configures the boot, swap, and dump devices to use persistent DSFs, as
described in Installing versus Updating
.
• By default, native multi-pathing is enabled for legacy DSFs. I/O requests directed to a legacy DSF may be
silently routed through a different lunpath. This change affects LVM alternate link behavior as well as third-
party multi-pathing products. You can restore the legacy behavior using the scsimgr command, as
described in Disabling Multi-Pathing on Legacy DSFs
.
• Replacing an internal disk or a disk in a JBOD requires additional steps to notify the mass storage stack,
as described in Changes to Existing Procedures: Replacing a Disk
.
Note: Legacy mode is deprecated in HP-UX 11i v3. Refer to the HP-UX 11i Version 3 Release Notes for a
complete list of deprecated features.
Coexistence
The agile view of mass storage supersedes the existing legacy view. However, in HP-UX 11i v3 the two views can
exist in parallel. The behavior of existing legacy DSFs is not affected by any persistent DSFs on the same server.
All mass storage commands are backward compatible and function with either legacy or persistent DSFs, except
as described in Backward Compatibility
. Most applications that support both legacy and persistent DSFs support a
mix of legacy and persistent DSFs.
Installing versus Updating
If you cold-install HP-UX 11i v3, both legacy and persistent DSFs are automatically created. By default, the
installation process configures system devices like the boot, root, swap, and dump devices to use persistent DSFs.
Configuration files such as /etc/fstab and /etc/lvmtab contain references to persistent DSFs.
If you update from HP-UX 11i v2 to 11i v3, existing legacy DSFs are retained and persistent DSFs are created.
Configuration files are not updated, so system devices continue to use the existing legacy DSFs.
The following table summarizes the differences between installing and updating to HP-UX 11i v3:
Cold install HP-UX 11i v3 Update to HP-UX 11i v3
Creates legacy DSFs Maintains existing legacy DSFs
Creates persistent DSFs Creates persistent DSFs
Creates system device configuration with persistent Maintains existing system device configuration with
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