关于IBM3584带库的path failover问题，请帮忙看下。
对带库不熟悉，网上搜索资料的时候说有control path failover和data path failover，而我lsdev输出如下：% lsdev -Cc tape # 省略一部分输出
rmt0Available 06-00-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt1Available 06-00-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt13 Available 06-01-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt14 Available 06-01-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt26 Available 05-00-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt27 Available 05-00-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt39 Available 05-01-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt40 Available 05-01-02 IBM 3580 Ultrium Tape Drive (FCP)
smc0Available 06-00-02 IBM 3584 Library Medium Changer (FCP)
smc1Available 06-01-02 IBM 3584 Library Medium Changer (FCP)
smc2Available 06-01-02 IBM 3584 Library Medium Changer (FCP)
smc3Available 05-00-02 IBM 3584 Library Medium Changer (FCP)
smc4Available 05-00-02 IBM 3584 Library Medium Changer (FCP)
smc5Available 05-01-02 IBM 3584 Library Medium Changer (FCP)
网上资料说，若没有PRI、ALT字样，则不支持自动路径failover，需要手动failover。我想知道，是安装驱动的时候，要选择自动failover功能，还是带库里面设置自动failover的？ First, you must ensure the failover setup ready at the library side. And then, run "#instAtape -a" to ask Atape driver to configure "Data path failover" and "Control path failover". For example,
# lsdev -Cc tape
rmt1 Available 0A-08-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt2 Available 0A-08-02 IBM 3592 Tape Drive (FCP)
rmt3 Available 0A-08-02 IBM 3580 Ultrium Tape Drive (FCP)
rmt4 Available 0A-08-02 IBM 3592 Tape Drive (FCP)
rmt5 Available 0A-08-02 IBM 3592 Tape Drive (FCP)
rmt6 Available 0A-08-02 IBM 3580 Ultrium Tape Drive (FCP)
smc0 Available 0A-08-02 IBM 3584 Library Medium Changer (FCP)
smc1 Available 0A-08-02 IBM 3584 Library Medium Changer (FCP)
smc2 Available 0A-08-02 IBM 3584 Library Medium Changer (FCP)
smc3 Available 0A-08-02 IBM 3584 Library Medium Changer (FCP)
smc4 Available 0A-08-02 IBM 3584 Library Medium Changer (FCP)
The attribute of "alt_pathing" shows the multiple path failover not support yet.
# lsattr -Elrmt2
FIPS_code FIPS Drive Code False
alt_pathing no Enable Alternate Pathing Support True
# lsattr -Elsmc0
alt_pathing no Enable Alternate Pathing Support True
Run instAtape command to setup the failover
# instAtape -a
Setting alternate pathing support on rmt1...
rmt1 changed
Setting alternate pathing support on smc0...
smc0 changed
Setting alternate pathing support on rmt2...
rmt2 changed
Setting alternate pathing support on smc1...
smc1 changed
Setting alternate pathing support on rmt3...
rmt3 changed
Setting alternate pathing support on smc2...
smc2 changed
Setting alternate pathing support on rmt4...
rmt4 changed
Setting alternate pathing support on rmt5...
rmt5 changed
Setting alternate pathing support on smc3...
smc3 changed
Setting alternate pathing support on rmt6...
rmt6 changed
Setting alternate pathing support on smc4...
smc4 changed
You can see "PRI" (primary path) and "ALT"(alternate path) now.
# lsdev -Cc tape
rmt1 Available 0A-08-02-PRI IBM 3580 Ultrium Tape Drive (FCP)
rmt2 Available 0A-08-02-PRI IBM 3592 Tape Drive (FCP)
rmt3 Available 0A-08-02-PRI IBM 3580 Ultrium Tape Drive (FCP)
rmt4 Available 0A-08-02-PRI IBM 3592 Tape Drive (FCP)
rmt5 Available 0A-08-02-PRI IBM 3592 Tape Drive (FCP)
rmt6 Available 0A-08-02-ALT IBM 3580 Ultrium Tape Drive (FCP)
smc0 Available 0A-08-02-PRI IBM 3584 Library Medium Changer (FCP)
smc1 Available 0A-08-02-PRI IBM 3584 Library Medium Changer (FCP)
smc2 Available 0A-08-02-ALT IBM 3584 Library Medium Changer (FCP)
smc3 Available 0A-08-02-ALT IBM 3584 Library Medium Changer (FCP)
smc4 Available 0A-08-02-ALT IBM 3584 Library Medium Changer (FCP)
The attribute is updated automatically.
# lsattr -Elrmt2
FIPS_code FIPS Drive Code False
alt_pathing yes Enable Alternate Pathing Support True
# lsattr -Elsmc0
alt_pathing yes Enable Alternate Pathing Support True
Run itdt to display the paths:
itdt -f /dev/smc0 path
Querying SCSI paths...
Total paths configured........... 3
Primary Path Number 1
Logical Device................. smc0
Product Identification......... 03584L32
Serial Number.................. 0000000T0039040
Host Bus Adapter............... fscsi0
Control Path Drive............. rmt1
Dynamic Tracking Enabled....... No
SCSI Channel................... 0
FCP SCSI ID.................... 0x611500
FCP Logical Unit............... 0x1000000000000
FCP World Wide Port Name....... 0x500507630059f00a
FCP World Wide Node Name....... 0x500507630019f00a
Path Enabled................... Yes
Path Manually Disabled......... No
Alternate Path Number 2
Logical Device................. smc2
Product Identification......... 03584L32
Serial Number.................. 0000000T0039040
Host Bus Adapter............... fscsi0
Control Path Drive............. rmt3
Dynamic Tracking Enabled....... No
SCSI Channel................... 0
FCP SCSI ID.................... 0x611c00
FCP Logical Unit............... 0x1000000000000
FCP World Wide Port Name....... 0x500507630099f00b
FCP World Wide Node Name....... 0x500507630019f00b
Path Enabled................... Yes
Path Manually Disabled......... No
Alternate Path Number 3
Logical Device................. smc4
Product Identification......... 03584L32
Serial Number.................. 0000000T0039040
Host Bus Adapter............... fscsi0
Control Path Drive............. rmt6
Dynamic Tracking Enabled....... No
SCSI Channel................... 0
FCP SCSI ID.................... 0x611f00
FCP Logical Unit............... 0x1000000000000
FCP World Wide Port Name....... 0x500507630059f00b
FCP World Wide Node Name....... 0x500507630019f00b
Path Enabled................... Yes
Path Manually Disabled......... No
Current path.....................1
Exit with code: 0
For more details, read the sections of "Control Path Failover Support for Tape Libraries" and "Data Path Failover and Load Balancing Support for Tape Drives" in Chapter 2 in IBM DD IUG http://www-01.ibm.com/support/docview.wss?rs=577&uid=ssg1S7002972 回复 3# sun_up
谢谢。 回复 2# sun_up
请问，如果用NBU的话，需要配置path failover么？ 因为我看nbu的jnpSA的media monitor里面都能显示每个driver有多少个设备。 The above failover feature is provided from IBM tape device driver. To bring out the failover, you have to install IBM tape driver to run with NBU.
And, it is transparent to the application. In the other word, the application doesn't see any failover which runs inside driver in the kernel.
NBU may have its own failover runing at the apllication level.
哦。谢谢了。就是如果使用NBU的话，因为其有自己的failover机制，所以不用在atape驱动这里设置failover了。 Yes, you can use either one or both. The failover mechanism is different between an application and a driver.
How does an application complete its failover? You can image a device with two paths as two houses. The application opens the door to a house, works inside but fails, closes the door, goes to the other house, opens the door, repeats its previous work, and continues next work.
How does a driver finish its failover? You image a device with two paths as two rooms at a house. When the driver fails to work at a room, it walks to the other room to repeats its previous work, and continues next work. If you have more paths (rooms), the driver works around these rooms. So, you can see the failover inside a driver more simple, more quick, more effective.
Also, more than a WRITE SCSI command may be sent to the tape drive when an application asks a write operation for a big data for example to write 3 MB data. When this write operation fails, the application doesn't know which WRITE SCSI command is failed and has to re-write all of 3 MB data. For a driver, it knows the failure occurs on which WRITE command, and just retry this WRITE command.
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