Solved: Re: Cisco UCS iSCSI Boot SLOW

navasysop · ‎06-07-2023

Have iSCSI Boot configured on UCS on code level 4.1(3).

UCS-FI-6248UP FI's and M5 Blades.

iSCSI Boot is working, but is SLOW. After server is booted the speed is what would be expected.

10g to the NAS controllers. Not using Appliance Ports.

Kirk J · ‎06-07-2023

A lot of times iSCSI will install ok even if there are MTU mismatches, but once regular OS/kernel is loading then MTU mismatches can cause boots to either fail or crawl. Need to make sure you don't have MTU issues (i.e. set your ESXi vmk initiator and vswitch to 1500 mtu for now). Also need to make sure you don't have some l1/l2 issuing causing lots of CRCs/drops.

Have seen some super slow boots due to lack of perennial reservations (https://kb.vmware.com/s/article/1016106)

You might want to spin up wireshark in combination with esxi's pktcap-uw (https://kb.vmware.com/s/article/2051814) and see if you are getting lots of retransmits, etc., although that may not be feasible during boot, and require an upstream capture for boot sequence.

Kirk...

View solution in original post

Kirk J · ‎06-07-2023

A lot of times iSCSI will install ok even if there are MTU mismatches, but once regular OS/kernel is loading then MTU mismatches can cause boots to either fail or crawl. Need to make sure you don't have MTU issues (i.e. set your ESXi vmk initiator and vswitch to 1500 mtu for now). Also need to make sure you don't have some l1/l2 issuing causing lots of CRCs/drops.

Have seen some super slow boots due to lack of perennial reservations (https://kb.vmware.com/s/article/1016106)

You might want to spin up wireshark in combination with esxi's pktcap-uw (https://kb.vmware.com/s/article/2051814) and see if you are getting lots of retransmits, etc., although that may not be feasible during boot, and require an upstream capture for boot sequence.

Kirk...

navasysop · ‎09-25-2023

After enabling Jumbo Frames on the UCS and Switch and Storage Device/NAS all is super fast.