Dual hosted Sun StorageTek 3320 JBOD in Single-Bus configurations may experience parity errors.

Asset ID:	1-73-1019436.1
Update Date:	2010-09-15
Keywords:

Solution Type FAB (standard) Sure

Solution 1019436.1 : Dual hosted Sun StorageTek 3320 JBOD in Single-Bus configurations may experience parity errors.

Impact

Parity errors (0x47/0x48) on the Sun StorageTek 3320 JBOD are due to a signal reflection effect on the SCSI bus. This is referred to as impedance discontinuity. In short, part of the signal is reflected back to its origin rather then carried all the way to the far end of the wire. To begin with, the 3320 Arrays have a marginal signal quality issue that is inherent in the hardware design. By cabling the array into a Single-Bus configuration the already marginal signal is exacerbated which results in multiple sources of impedance discontinuity. Any discontinuity in impedance causes a reflection effect. Multiple discontinuity increases this impact. Adding an additional host on the same bus increases discontinuity resulting in parity errors (0x47/0x48).

While dual hosted, cabling the array into a Split-Bus configuration will reduce the amount of discontinuity of the impedance. Resulting in no parity errors (0x47/0x48) due to a signal reflection effect on the SCSI bus.

Contributing Factors

Any Sun StorageTek 3320 SCSI Array in a dual hosted Single-Bus JBOD configuration is impacted by this issue.

Symptoms

With the Sun StorageTek 3320 SCSI Array in a dual hosted Single-Bus JBOD configuration you may receive the following errors:

Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.warning] WARNING: /pci@7c0/pci@0/pci@1/pci@0,2/scsi@1 (mpt1):
Oct 22 10:59:32 sdpm2031 Target 0 reverting to async. mode
Oct 22 10:59:32 sdpm2031 mpt: [ID 675377 kern.warning] WARNING: ID[SUNWpd.mpt.sync_wide_backoff.6013]
Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.warning] WARNING: /pci@7c0/pci@0/pci@1/pci@0,2/scsi@1/sd@0,0 (sd1):
Oct 22 10:59:32 sdpm2031 Error for Command: inquiry   Error Level: Retryable
Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.notice] Requested Block: 0 Error Block: 0
Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.notice] Vendor: SEAGATE Serial Number: 070653N2EV
Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.notice] Sense Key: Aborted Command
Oct 22 10:59:32 sdpm2031 scsi: [ID 107833 kern.notice] ASC: 0x48 (initiator detected error message received), ASCQ: 0x0, FRU: 0x2

- or -

Oct 22 10:25:20 sdpm2031 mpt: [ID 675377 kern.warning] WARNING: ID[SUNWpd.mpt.sync_wide_backoff.6013]
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.warning] WARNING: /pci@7c0/pci@0/pci@1/pci@0,2/scsi@1/sd@8,0 (sd11):
Oct 22 10:25:20 sdpm2031 Error for Command: write(10)   Error Level: Retryable
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.notice] Requested Block: 19540012   Error Block: 19540012
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.notice] Vendor: FUJITSU Serial Number: 0715D02PEK
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.notice] Sense Key: Aborted Command
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.notice] ASC: 0x47 (scsi parity error), ASCQ: 0x0, FRU: 0x0
Oct 22 10:25:20 sdpm2031 scsi: [ID 107833 kern.warning] WARNING: /pci@7c0/pci@0/pci@1/pci@0,2/scsi@1 (mpt1):
Oct 22 10:25:20 sdpm2031 Target 8 reverting to async. mode
Oct 22 10:25:20 sdpm2031 mpt: [ID 675377 kern.warning] WARNING: ID[SUNWpd.mpt.sync_wide_backoff.6013]

Root Cause

Parity errors (0x47/0x48) are due to impedance discontinuity. In short the signal is reflected back to it's origin rather then transmitted to the far end of the wire. While in a Single-Bus configuration there are multiple sources if impedance discontinuity in close proximity. Any discontinuity of the impedance will result in the reflection effect.

These errors were discovered at a customer during boot. After extensive testing it was determined cabling the JBOD arrays into a Split-Bus configuration will reduce the amount of discontinuity of the impedance, resulting in no parity errors due to signal reflection effect on the SCSI bus.

Corrective Action

Workaround:

Cable dual hosted Sun StorageTek 3320 JBOD configurations into Split-Bus mode.

Resolution:

Dual hosted Single-Bus dual configurations are no longer supported. Cabling the array into Split-Bus mode using 2 meter cables is the current supported method for all new installations.

Please refer to the Sun StorEdge 3000 Family Installation, Operation and Service Manual (Sun P/N 819-1274-13), page B-8, FIGURE B-4, for step-by-step instructions on cabling the array into Split-Bus mode.

References:

    BugID: 6632802
    Escalation ID: 1-22854279
    Reference Manual: 819-1274-13

For information about FAB documents, its release processes, implementation strategies and billing information, go to the following URL:

http://tns.central/fab

For Sun Authorized Service Providers go to:

http://tns.central/SPE/fab/

In addition to the above you may email:

FAB-Manager@sun.com

Internal Contributor/submitter
Michael.Martinez@Sun.COM

Internal Eng Responsible Engineer
Michael.Martinez@Sun.COM Responsible Manager: Tejinder.Singh@Sun.COM

Internal Services Knowledge Engineer
Joe.Davis@Sun.COM

Internal Eng Business Unit Group
NWS (Storage)

Internal Sun Alert & FAB Admin Info
10-Jul-2008: Completed draft and sent to Extended Review.
14-Jul-2008: No feedback from Ext Rvw - sending to Publish.
04-Aug-2008: Chgd all instances of 3120 to 3320 per Submitter request.
12-Jan-2010: Corrected Product Name to swoRDFish inconsistency.

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