FreeBSD panic detail

Here's what's written on the console of the server:

Ad4: TIMEOUT – READ_DA retrying (2 retries left) LBA=353589343
Ad4: WARNING – removed from configuration
Sata2-master: FAILURE – READ_DMA timed out
Spec_getpages: (ad4s1f) I/) read failure: (error=6 bp 0xd6302074 vp xc26a2610 size: 65536, a_count: 65536,valid: 0x0 nread: 0, reqpae: 0, pindex: 192, pcount: 16
Vm_Fault: pager read error, poid 40823 (cp)
Panic: softdep_setup_freeblcks: inode busy
Uptime: 11d13h29m53s