HP Integrity VM Accelerated Virtual I/O Overview

feature helps to prevent the guest from corrupting a disk, if the replacement was not intentional. In
order to validate the replacement, the guest administrator can use the replace_dsk functionality of
gvsdmgr(1M) on 11iv2 Guests or the replace_wwid/replace_leg_dsf functionality of scsimgr(1M) on
11iv3 Guests.
AVIO File backing stores commit the written data to the host disk before returning success to the guest.
This feature helps prevent data corruption on the guest disk, if the VM host were to crash or panic
after the guest write but before the host buffer cache has been flushed to the host disk.
Native Multi-pathing and Persistent DSFs
With Integrity VM 4.0, native host multi-pathing on the VM Host system benefits virtual machines
running all guest OSes. Some of the benefits of native multi-pathing are:
• optimal distribution of I/O traffic across lunpaths to LUNs,
• dynamic discovery of lunpaths and LUNs,
• automatic monitoring of lunpaths,
• automatic lunpath failover and recovery,
• intelligent I/O retry algorithms to deal with failed lunpaths,
• lunpath authentication to avoid data corruption.
The customer should configure guest storage with persistent device special files DSFs rather than use
“legacy” DSFs. The utility hpvmdevtranslate(1m) can be used to convert guest configurations from
legacy to persistent DSFs (see the Integrity VM Installation manual for further details). Refer to “HP-UX
11iv3 Native Multi-pathing for Mass Storage” whitepaper at http://docs.hp.com for further
information.
Dynamic detection of backing store attribute changes
AVIO supports dynamic detection of LUN attribute changes for HP-UX 11iv3 guests. For example,
when the host backing store goes offline, the guest dynamically detects the state change and the guest
LUN goes to offline state. Similarly when the backing store comes back online, the LUN becomes
online in the guest.
AVIO supports online expansion of backing store capacity. 11iv3 AVIO guest dynamically detects
backing store capacity increase and makes the additional space available in the guest.
WARNING: You should not dynamically expand the size of logical volume backing stores that serve
as the root disk for guests. This will cause the guest to no longer boot. Raw backing store for root
disks in a guest will support dynamic LUN expansion.
AVIO supports dynamic discovery of LUNs in the guest. When new guest LUNs are added using
hpvmmodify, these are automatically discovered in the 11iv3 guest and no ioscan is needed in the
guest.
Enhanced IO Retry and Error Policies
AVIO storage driver uses the inbuilt retry policies of the HP-UX 11iv3 host storage stack while
preventing guest io hangs. This can result in timely IO completions in the presence of device errors.
This also provides for faster failovers in Serviceguard configurations.