PowerVault ME4: Update to maximum SCSI persistent registrations for linear storage.
Summary: The current ME4 support matrix shows the per iSCSI LUN: 85-128 depending on IQN length, field data shows that usually the limit for persistent reservations will be nearer to 85 limit with conventional IQN names. ...
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Symptoms
The problem appears when we try to register an additional key on any device you will get the following response:
open /dev/tdmpk with flags=0x800 inquiry cdb: 12 00 00 00 24 00 duration=0 ms DellEMC VA4 G280 Peripheral device type: disk open /dev/tdmpk with flags=0x802 Persistent Reservation Out cmd: 5f 06 00 00 00 00 00 00 18 00 Persistent Reservation Out parameters: 00 00 00 00 00 00 00 00 00 54 44 00 00 00 00 00 00 ........TD...... 10 00 00 00 00 00 00 00 00 ........ duration=0 ms persistent reserve out: Fixed format, current; Sense key: Unit Attention Additional sense: Reservations preempted Raw sense data (in hex): 70 00 06 00 00 00 00 0e 00 00 00 00 2a 03 00 00 00 00 00 00 00 00 PR out (Register and ignore existing key): Unit attention sense key
All registrations prior to hitting the limit will work.
Cause
The iSCSI linear reservation limit is based on the IQN name length of the initiator. Based on observation in most instances IQN names that adhere to the iSCSI specification will cause this limit to be reach at the low end of the 85-128 value listed in the PowerVault ME4 support matrix.
Resolution
To be able to get to the maximum value of 128 the user must manually create IQN names that are no longer than 14 bytes.
An example would be: "iqn.1991-05.k" while this does not meet the iSCSI specifications the array will accept it and allow for more reservations.
Affected Products
Dell EMC PowerVault ME4012, Dell EMC PowerVault ME4024, Dell EMC PowerVault ME4084Products
ME Series, OEMR ME40XX and ME4XXArticle Properties
Article Number: 000198588
Article Type: Solution
Last Modified: 20 Jul 2023
Version: 5
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