Replacing a failed and degraded virtual disk on Dell T110 II RAID 1 PERC S300
There isn't enough information from those events to know for certain what's going on. I would guess that the drive went offline and into a "failed" state at one point, then was reset in some way which brought it back online normally.
I would recommend that you look back through the event history a bit further for more events on physical disk 0:0 to see what triggered the initial problem. If you see a lot of Sense Key 3/11/00 or 4/xx/xx errors leading up to the failure, that's a pretty sure sign you should consider replacing it. Otherwise, you could always try reseating the drive to see if the system will start a "rebuild", or possibly reboot w/ the drive removed and set after things are up and running.
With this type of controller, I think you can even sometimes end up stuck with having to re-initialize the RAID from the BIOS and reinstall the OS to clear things up entirely. I'd recommend ensuring your driver and FW revisions are up-to-date before resorting to that (plus calling Dell support for other suggestions and assistance).