Unable to establish new or existing paths to iSCSI datastores, due to all channel slots being consumed

Products

• VMware vSphere ESXi
• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x

Issue/Introduction

• When presenting new iSCSI devices some ESXi hosts
  • May be unable to establish paths to the storage device
  • May not see all expected paths to the devices 

 

Environment

VMware vSphere ESXi 

Cause

If a given iSCSI target is presented to ESXi via a very large number of IPs, ESXi may not have sufficient channel slots to probe for all possible paths to a LUN.

If a LUN is, in fact, accessible only via a subset of those IPs, the host may have exhausted its channel slots without discovering all or any or the expected paths to a LUN. 

 

In the ESXi: /var/run/log/syslog.log we can see logging "Error: All Channel Cache Slots Taken"

####-##-##T##:##:##.###Z iscsid[2098737] Login Target: iqn.1992-08.com.######:####################################### if=default addr=##.#.##.###:3260 (TPGT:#### ISID:0xd3)
####-##-##T##:##:##.###Z iscsid[2098737] Error: All Channel Cache Slots Taken
####-##-##T##:##:##.###Z iscsid[2098737] VmIscsi_SetUpBindings: Failed to assign Target/channel ID  error=-1
####-##-##T##:##:##.###Z iscsid[2098737] __session_create: Failed to assign session binding parameters
####-##-##T##:##:##.###Z iscsid[2098737] session login failed with error 5,retryCount=0
####-##-##T##:##:##.###Z iscsid[2098737] Login Target Failed: iqn.1992-08.com.######:####################################### if=default addr=##.#.##.###:3260 (TPGT:#### ISID:0xd3) err=5
####-##-##T##:##:##.###Z iscsid[2098737] Login Failed: iqn.1992-08.com.######:####################################### if=default addr=##.#.##.###:3260 (TPGT:#### ISID:0xd3) Reason: 00050000 Initiator Error: (0x0005 Login failure due to target-response.)

Resolution

Contact the storage vendor to review the iSCSI storage presentation and configuration to limit the number of IPs via which a given iSCSI target is accessible.