IBM Support

SCSI WRITE SAME SCSI Busy (1370) Error

Flashes (Alerts)


Abstract

IBM Spectrum Virtualize software release 8.1 introduced the SCSI UNMAP and WRITE SAME functions to the IBM FlashSystem V840/V9000 and IBM SAN Volume Controller (SVC) products.

An issue with the IBM FlashSystem storage enclosure and IBM Spectrum Virtualize communications has surfaced when a certain combination of the new introduced commands is processed.

When WRITE SAME all zeros without UNMAP are sent from the SVC or FlashSystem V840/V9000 controller, the FlashSystem storage enclosure may have problems in processing those commands. This can lead to frequent 1370 SCSI ERP errors and 1220 port excluded errors on the controller. Hosts which generate large workloads of zeros are exposed. As example IBMi.

Content

SYSTEMS EFFECTED

· FlashSystem V9000 (9846/9848) running 8.1.x.x with attached FlashSystem 840/900 (9840/9843) AE1 / AE2 / AE3

· FlashSystem V840 (9846/9848) running 8.1.x.x with attached FlashSystem 840/900 (9840/9843) AE1 / AE2 / AE3

· SVC with 8.1.x.x with attached FlashSystem 840/900 (9840/9843) AE1 / AE2 / AE3



DESCRIPTION
Hosts which generate large workloads of zeros are exposed - in IBM Spectrum Virtualize version 8.1 and above - to a problem with the way the IBM FlashSystem storage enclosure handles SCSI WRITE SAME commands without the UNMAP bit set.

With the introduction of SCSI UNMAP and WRITE SAME functions in version 8.1, the SVC and FlashSystem V840/V9000 controller internal component which handles communication with back-end storage controllers, was altered to convert 0 writes from hosts to SCSI WRITE SAME without UNMAP.

The IBM FlashSystem storage enclosure have a problem in processing these commands and as a result may return SCSI Busy (1370) errors back to the SVC or FlashSystem V840/V9000 controller if the FlashSystem storage enclosure is too busy. An accumulation of these SCSI Busy errors can result in SVC or FlashSystem V840/V9000 controller excluding the port (1220 error).




MITIGATION
Contact IBM Support to upgrade to an 8.1.x iFix which is now available for the FlashSystem V840/V9000 and SAN Volume Controller systems.
The iFix prevents the FlashSystem V840/V9000 and SAN Volume Controller systems from converting "0" (zero) writes from hosts to SCSI WRITE SAME without UNMAP.
SVC/V840/V9000 version 8.1.3.0 and later also have the mitigation. 
The issue is fixed in the 840/900 flash enclosure in 1.5.2.0 and 1.6.0.0 and later firmware.

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Document Information

Modified date:
17 February 2023

UID

ssg1S1012299

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