Many data centers that have been around for years tend to loose their organization and get messy. That is not unique. When I travel I find that many people that have underfloor messes are moving to overhead systems and vice versa in efforts to organize their data centers. Trunking cables can assist. These are factory pre-terminated cables with several wrapped in a jacket. You can install these and when all equipment is connected anything not in the common jacket can be removed.
You will certainly want to plan for the cleanup. If you have the luxury of being able to schedule some downtime, that is a bonus. You can use the same time to rearrange your equipment, move racks together to block airflow from the hot aisles into the cold aisles, etc.
If you don't have that luxury, then you may have to run on a redundant site for a while, or remediate portions of the data center at a time using your failover mechanisms. You will likely, however, be somewhat vulnerable without your primary or backup systems (depending on which you are remediating) so plan carefully. It may even be in your best interest to rent some temporary equipment to use during the fix. You can also use this time to test your disaster recovery plan.
ABOUT THE AUTHOR: As the Global Network Applications Market at The Siemon Company, Carrie Higbie supports the end-user and electronics communities. She has won the "Communication News" Editor's Choice Award for the last two years.