The Effect of Device Replacement on Agile Device Files

ManualsBrandsHP ManualsSoftwareHP-UX 11i v3 Mission-Critical OE

The Effect of Device Replacement on Agile

Device Files

Technical white paper

Table of contents

Abstract.............................................................................................................................................. 2

Understanding device discovery ............................................................................................................ 2

Field Replaceable Units ........................................................................................................................ 6

Verifying if spoofing is supported..................................................................................................... 10

Effect of io_redirect_dsf or replace_wwid on pass-thru dsf....................................................................... 10

Glossary........................................................................................................................................... 10

For more information.......................................................................................................................... 11

Providing comments to HP .................................................................................................................. 11

Summary of content (12 pages)

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The Effect of Device Replacement on Agile Device Files Technical white paper Table of contents Abstract.............................................................................................................................................. 2 Understanding device discovery ............................................................................................................ 2 Field Replaceable Units ................................................................................................
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Abstract The agile naming scheme for mass storage devices was introduced in HP-UX 11i v3, which addressed the limitations of the device naming scheme used in previous releases of HP-UX 11i. This paper explains how online device replacements effect agile device files. In addition, this paper is intended for system administrators who have basic knowledge of mass storage device naming on HP-UX 11i v3.
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Figure 1: Single path to a LUN The following is the output from the ioscan command for the configuration in Figure 1: # ioscan –m lun /dev/rdisk/disk1 disk HSV210 1 64000/0xfa00/0xa esdisk CLAIMED DEVICE online HP 0/1/0/0.0x0x500508b3009097f9.0x4001000000000000 /dev/disk/disk1 /dev/rdisk/disk1 In this command output, the handle 64000/0xfa00/0xa is associated with the LU name 0x600508b3009097f0421745217a6c0057 and device instance number 1.
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Figure 2: Multiple paths to a LUN The following ioscan command output shows two lunpaths for disk1: # ioscan –m lun /dev/rdisk/disk1 disk HSV210 1 64000/0xfa00/0xa esdisk CLAIMED DEVICE online HP 0/1/0/0.0x0x500508b3009097f9.0x4001000000000000 0/1/0/0.0x0x500508b3009097f1.0x4001000000000000 /dev/disk/disk1 /dev/rdisk/disk1 In Figure 3, when an LU is replaced, the LU name to LUN mapping changes.
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Note: When using the scsimgr replace_wwid command, if you do not specify the dsf keyword, a new device file is created. If you specify the dsf keyword, the existing dsf is retained. For information on the replace_wwid keyword, see scsimgr(1M).
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LUN path : lunpath11 Class Instance Hardware path SCSI transport protocol State Last Open or Close state = = = = = = lunpath 11 0/1/0/0.0x500508b3009097f9.0x4001000000000000 fibre_channel UNOPEN AUTH_FAILED LUN path : lunpath12 Class Instance Hardware path SCSI transport protocol State Last Open or Close state = = = = = = lunpath 12 0/1/0/0.0x500508b3009097f1.0x4001000000000000 fibre_channel UNOPEN AUTH_FAILED Field Replaceable Units Tape failures often result in FRU replacement.
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Figure 4: Original configuration 7
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Figure 5 shows FRU replacement with no spoofing. Figure 5: FRU Replacement (No spoofing) If spoofing of the target World Wide Name and LUN WWID is not supported, replacement results in the detection of a new device (a new tape has a new WWID); a new LU and a new target are presented to HP-UX. Because neither the LU nor the mapping of LUN to LU is known, HP-UX creates a new device special file. No authentication failure is flagged in this case.
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Figure 6 shows FRU replacement with spoofing. Figure 6: FRU Replacement (with target WWN spoofing) Even though both the target and the LU are replaced, because the device is spoofing the old target name (WWN), the target path does not change. However, because of the LUN-LU mapping change, HP-UX detects a new LU behind the target and flags this as an authentication failure.
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Verifying if spoofing is supported If spoofing is not supported, the host sees an increase in the number of target paths and lunpaths.
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For more information To read more about HP-UX mass storage, go to http://www.hp.com/go/hpux-core-docs. Click on the HP-UX version you want. Then, scroll down to the White papers section. Providing comments to HP HP welcomes your input. Please give us comments about this white paper, or suggestions for the mass storage or related documentation, through our technical documentation feedback website: http://www.hp.com/bizsupport/feedback/ww/webfeedback.
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