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This article will explain in detail how to solve the failure of DISK OPERATION ERROR switch cascaded single-mode optical fiber link. The content of the article is of high quality, so the editor will share it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

Problem description

Two IBM DS6800 are placed in the main center computer room and disaster recovery computer room respectively. Through the cascade of B5000 and McData4400 fiber exchange, the disaster recovery of LVM is realized. The two switches are connected by single-mode fiber, and the physical distance between the two computer rooms is about 3.5 km.

Because the construction of other units leads to the interruption of single-mode optical fiber, after the communication company repairs the fault, the connection of single-mode optical fiber is restored, which may be due to the increase of optical fiber connection nodes or the problem of connection quality. the loss of optical fiber link reaching 8.23DB.1 km is about 1DB. The single-mode module of the disaster recovery center is 4KM, so although the connection is open, there are continuous connection failures in the middle, resulting in disk errors reported by the operating system layer.

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# errpt

DCB479971118230710 T H hdisk86DISK OPERATION ERROR

DCB479971118211010 T H hdisk86DISK OPERATION ERROR

DC73C03A1118143810 T S fscsi0SOFTWARE PROGRAM ERROR

DC73C03A1118143810 T S fscsi0SOFTWARE PROGRAM ERROR

D666A8C71118143810 T H fcs0ADAPTER ERROR

DC73C03A1118143810 T S fscsi0SOFTWARE PROGRAM ERROR

DC73C03A1118143810 T S fscsi0SOFTWARE PROGRAM ERROR

D666A8C71118143810 T H fcs0ADAPTER ERROR

D666A8C71118143710 T H fcs0ADAPTER ERROR

C62E1EB71118143610 P H hdisk86DISK OPERATION ERROR

……

As mentioned above, AIX keeps reporting errors, reporting errors of 'DISK OPERATION ERROR'' almost every minute.

# datapath query device

DEV#:2DEVICE NAME: vpath3TYPE: 1750500POLICY:Optimized

SERIAL: 68947310208

=

Path#Adapter/Hard DiskStateModeSelectErrors

0fscsi0/hdisk86OPENNORMAL 2743907375193

1fscsi0/hdisk88OPENNORMAL00

2fscsi1/hdisk94OPENNORMAL 294658485810

3fscsi1/hdisk96OPENNORMAL00

We can see that the four links stored to the host are all open/normal states. But errors is growing.

The Hdisk86 is connected through a fcs0 device, so check the link first

# lscfg-vl fcs0

Device Specific. (Z8). 20000000C98F0996

... ...

Hardware Location Code.U5802.001.0080624-P1-C4-T1

Analysis of problems

Based on the wwn (20000000C98F0996) of the HBA card, we determined the fiber switch to which it is connected. This switch is the one with the link problem; then check that the disks that connect the IBM DS6800 to the aix host through this switch are reporting errors. Thus, it is determined that the signal attenuation after the link is restored is more than before, which leads to the failure of transmission instability of the connection of the link.

Problem solving

Replace the single-mode module of the disaster recovery center, from the original 4km to the single-mode module of 10km. After half an hour of observation, the OS layer no longer reported the error of 'DISK OPERATION ERROR', and the problem was solved.

The attenuation range of the connection of single-mode optical fiber is 5-18. At present, the attenuation of this link is in the normal range. The problem lies in the choice of single-mode module. The single-mode module of the disaster recovery center is 4KM, so it can not achieve normal and stable communication. After replacing it with 10km, the link returns to normal.

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