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As I understand it one can upgrade the firmware on a Dell Equallogic server in about 15 seconds and it can be done whilst an ESXi host is connected and VMs are running but that the iSCSI timeout value needs to be increased to avoid errors on guest VMs.

I've searched VMWare and Dell's sites but can't find a best practice quide or KB article that gives details of what to do for ESXi 5.0 in order to increase the timeout and perform a "live" firmware upgrade. Is it per-host/iSCSI initiator or per target, how do you increase it and what is a sensible value?

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According to the docs it should be the "Session Recovery Timeout" parameter. But keep in mind that the guest OS's would have their own timeouts - these might need a change as well.

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Dell/Equallogic actually recommends increasing the iSCSI "LoginTimeout" value to 60 seconds for each Equallogic group IP accessed by each ESX host.

The steps below detail the recommended method, though you can also perform this globally on the iSCSI initiator as a whole (applies to all groups/iSCSI SANs being accessed).

  1. Log in to the vSphere Client and select a host
  2. Navigate to the "Configuration" tab
  3. Select "Storage Adapters"
  4. Select the iSCSI vmhba to be modified (typically the iSCSI software initiator)
  5. Click "Properties"
  6. Select the "Dynamic Discovery" tab
  7. Select the IP address for the Equallogic group
  8. Click "Settings"
  9. Click "Advanced"
  10. Scroll to "LoginTimeout" and set the value to 60
  11. Repeat 1-10 for all applicable hosts/servers
  12. Host reboot is necessary to apply changes

Value can also be modified via command line:

esxcli iscsi adapter param set -A vmhbaXX -k LoginTimeout -v 60

The firmware update on an Equallogic storage array involves a failover operation from active to passive controller module. This typically causes a loss of access for 15-30 seconds, which is well within the recommended timeout value range. It's usually best to get these settings right and test this process before an environment is in production.

VMware ESX Reference: VMware KB 2007829

Dell Equallogic Reference: iSCSI Initiator and OS Considerations (requires support account access)

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