You got transport error.

I'd power down the server. Re-seat all the disks make sure they are securely connected to the server.

/dev/rdsk/c1t1d0s7 disks probably contains the application home, it was complaining during bootup. check your vfstab file under /etc

cat /etc/vfstab | grep c1t1d0s7

or
cat /etc/vfstab |grep <application home directory> to see where it's mounted or what is mounted to c1t1d0s7

if you are lucky maybe errors in vfstab, otherwise disk crash means restore from backup tape.

Also I'm guessing here that you could be using disks with different RPM speeds hence
"Target 9 reducing sync, transfer rate" the faster disk will always spin down to the RPM speed of the slowest disk.