I have done this exact thing on a DL360 G5 and it works fine. As other replies noted, you have to make sure your array controller cache has a good battery.
If the battery says it's bad (and that happens a lot on these older servers), it disables the write cache and it also disables other features like online expansion.
All you need to do is insert the new drives and then add all of them to the existing array. Once that's done you can do an online raid level migration with expansion.
It can take a while to do online migration/expansion, so be prepared for a few hours between when you start and when it's all done.
You can adjust the priority of the migration and expansion tasks in the advanced settings of the SSA utility but making it run at higher priority will affect the running system's I/O speed. If it's important to keep your apps running smoothly, leave it set at low priority and just let it take as long as it needs for each step.
If the battery says it's bad (and that happens a lot on these older servers), it disables the write cache and it also disables other features like online expansion.
All you need to do is insert the new drives and then add all of them to the existing array. Once that's done you can do an online raid level migration with expansion.
It can take a while to do online migration/expansion, so be prepared for a few hours between when you start and when it's all done.
You can adjust the priority of the migration and expansion tasks in the advanced settings of the SSA utility but making it run at higher priority will affect the running system's I/O speed. If it's important to keep your apps running smoothly, leave it set at low priority and just let it take as long as it needs for each step.