Upgrading 6807 VSS DUAL SUP

[Jo49201]

Hello we are planning to upgrade our two pairs of 6807 XL and I would like to question you guys about to point that i would like to confirm. 
DUAL SUP VSS (1 SUP in each chassis- SW1 and SW2)

Both VSS are running 15.2(1)SY2 and we will go to 15.5.1-SY8.

1. We will need to upgrade the ROMMON since we are one version behind. It doesn't seems to do any impact.
Appart from doing a switchover two times, it doesn't seems to have impact. Any lesson or comment about that procedure?
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/rommon/sup2t_sup6t_rommon.pdf

2.We will be going through the Fast Software Upgrades which has impact, i'm aware. I'm just trying to determine the impact. 

Already aware of the procedure: change boot variable, redundancy reload peer, redundancy force-switchover. 

I'm aware that the FPGA will need to be upgraded. Thank to Leo Laohoo multiple warning XD. 
I'm just wondering if the VSS will be able to go online after the reboot of the ''redundancy force-switchover''.
When we talk about FPGA we are mostly talking about the C6800-32P10G linecard?
So the VSS will be able to go up with it's supervisor. Both most of the data linecard will not go up?
That would mean, the downtime of the upgrade + the downtime of the linecard.

We only have VS-SUP2T-10G and C6800-32P10 in our VSS. One VSS pair has more C6800-32P10G that the other.

Would really appreciate your input on this  Leo Laohoo
Thank you. 

[Leo Laohoo]

Both chassis has C6800-32P10G so this means manual FPGA upgrade.  ISSU, FSU/eFSU/xFSU does not support FPGA upgrade so I can/will guarantee ISSU, FSU/eFSU/xFSU will fail 110%.  

My recommendation is to stick with the tried-n-tested method: 

1. Copy the IOS file into Active Supervisor Card
2. Copy the IOS file into Secondary Supervisor Card
3. Change the boot variable string to point to the new IOS version. 
4. Check the config-register is 0x2102
5. Perform an MD5 hash check of the IOS files to make sure they are not corrupt. 
6. Save the config
7. Reboot. 
8. Perform the FPGA upgrade to the C6800-32P10G.

[Leo Laohoo]

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@Jo49201 wrote:
When we talk about FPGA we are mostly talking about the C6800-32P10G linecard?
So the VSS will be able to go up with it's supervisor. Both most of the data linecard will not go up?

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C6800-32P10G will need to have an FPGA upgrade done manually. 

The C6800-32P10G will power up but will be disabled until the FPGA gets upgraded.  If I remembered correctly, this process will take around 7 minutes long.