iSCSI Boot from SAN

[Gaj Anna]

Hi All

We have a 5508 UCS 2.2 environment with two FI’s and two 5k Nexus switches. The iSCSI storage is attached to the nexus and currently used for data storage only. The storage (LUN) is presented to the ESXi hosts using separate a VLAN’s X and Y and eth interfaces 2 and 3 via FI A and B.  

We have a requirement to enable iSCSI boot. Does this require to configure separate eth interfaces 4 and 5  to be used for the overlay with iSCSI nics or can we use the same eth interfaces 2 and 3 (with a new native VLAN for iscsi boot) which is also used for the current iSCSI storage?

Any recommendation on best practice would be great.

Thanks, and Regards

GA

[Kirk J]

Greetings.

You've probably seen it, but please take a look through https://www.cisco.com/c/en/us/support/docs/servers-unified-computing/ucs-manager/116003-iscsi-ucs-config-00.html

Adding additional vnics/VMNICs has the potential for ESXi to shuffle your VMNIC order.

Are you planning on reinstalling ESXi to the BFS iSCSI LUNs?

You can use what ever vnics you want for iSCSI BFS except for the first one, which is generally bound to mgmt vmk0

Kirk...

[Gaj Anna]

Hi Kirk

Thanks for the feedback.

Probably will use the existing ethernet ports used for the iscsi storage and configure seperate native vlans for iscsi boot for each Fabric A and B side. Currently iscsi storage ethernet uplink ports are attached to the Nexus as access VLAN ports and thease also need to be re-configured as trunk with the native vlan.

Currently the ESXi is booted from a native FC SAN. We want to migrate this over to the iSCSI based SAN. Current plan is to reinstall ESXi in iSCSI for the blades to boot from. Is there a better way of doing this?

Regards

GA

[Kirk J]

As ESXi only takes minimal time to reinstall, that is usually a lot quicker and cheaper (vs some $$san boot LUN migration utility)

Not related to your iSCSI question, but one thing many customers overlook, is setting up a syslog server, and pointing ESXi to it.   It is very handy to have for troubleshooting purposes as ESXi is not very good at retaining logs after a PSOD or reboot.

Will your iSCSI boot target have a different IP or IQN than your existing shared ISCSI datastore LUNs ?

Kirk...

[Gaj Anna]

Hi Kirk

Thanks for the syslog tip.

Still at planning stage. The native vlan to be configured for iscsi boot will have a seperate IP schema than the iscsi storage. We havent discussed the options from the storage side team yet. The plan is to have a seperate IP schema, LUN and IQNs defined for boot. Any other best pratices please comment.

Regards

GA

[Kirk J]

Oh, if possible, and not already in plans, definitely setup jumbo frames.  We generally see a sizable (i.e. 25-30 %) boost in performance on iSCSI and NFS when jumbo frames are enabled.  UCS uses QOS/COS to set/allow MTU sizes, so you'll either need to flag the vnics with specific COS class and allow jumbo frames for it at QOS settings,, or set best effort to 9216, in addition to making sure your upstream switches and storage controller ports are configured for it as well.

Kirk..

[Gaj Anna]

Greta thanks Kirk for the brief and tips.