When booting a Dell PowerEdge Server with a RAID Controller, I came across an error that I’ve never encountered before. Upon booting the server, during POST, the server says “There are offline or missing virtual drives with preserved cache. Please check the cables to ensure that all drives are present. Press any key to enter the configuration utility”.
There is no way to go past POST without flushing or clearing the preserved cache in the controller BIOS according to a Dell article.
“The presence of Preserved Cache is obvious when the server is rebooted. A POST message is displayed that Preserved Cache is present. You will not be allowed to proceed past POST without flushing or clearing Preserved Cache in the controller BIOS. This can be done by entering the correct controller’s BIOS and pressing . Select Preserved Cache. If Preserved Cache is not a selectable option then preserved cache is not present. If it is selectable you can flush the cache to disk if the failed disk has been made healthy. If the disk cannot be made healthy the Preserved Cache must be cleared prior to regaining the ability to create a new array on that controller.” – see links below.
In order to resolve this, you select the RAID controller as per the image below, click F2 – operations, and select “Manage Preserved Cache”. Go through the prompts and it’ll eventually ask to delete the preserved cache of the disk(s) it is complaining about.
It turns out, the reason that I got this error was because of a failing drive that the server was still seeing as part of the server, was removed forcibly. Although the drive said it was failing, the block addresses were being retired, and all the virtual machines on that hard drive wouldn’t turn on anymore, it is a good idea to try to safely remove the disk if possible.
Thanks to Zeke Chen for helping while I was remote.