Following errors will show up in the offline analysis under hard drive analysis or under /var/log/messages file. 

Jan 31 21:05:59 <kern.crit> VPXHOSTNAME kernel: ad0: FAILURE - WRITE_DMA timed out LBA=11882751
Jan 31 21:05:59 <kern.crit> VPXHOSTNAME kernel: ad0: FAILURE - WRITE_DMA timed out LBA=11882783
Jan 31 22:03:59 <kern.crit> VPXHOSTNAME kernel: ad0: FAILURE - WRITE_DMA timed out LBA=27859423
Feb 1 18:04:45 <kern.crit> VPXHOSTNAME kernel: ad0: FAILURE - WRITE_DMA timed out LBA=27689727


Feb2017_09_07/var/log/messages:Jan 31 21:05:59 <kern.crit> VPXHOSTNAME kernel: g_vfs_done():ad0s1e[WRITE(offset=98304, length=16384)]error = 5
Feb2017_09_07/var/log/messages:Jan 31 21:05:59 <kern.crit> VPXHOSTNAME kernel: g_vfs_done():ad0s1e[WRITE(offset=114688, length=16384)]error = 5
Feb2017_09_07/var/log/messages:Jan 31 22:03:59 <kern.crit> VPXHOSTNAME kernel: g_vfs_done():ad0s1e[WRITE(offset=8180154368, length=4096)]error = 5
Feb2017_09_07/var/log/messages:Feb 1 18:04:45 <kern.crit> VPXHOSTNAME kernel: g_vfs_done():ad0s1e[WRITE(offset=8093270016, length=16384)]error = 5

These errors could also possibly cause the VPX to reboot unexpectedly.

Run the following command in the shell:

sysctl hw.ata.to=20

The command will increase the hard drive timeout of the VPX from 5 seconds to 20 seconds (maximum it can be set) on the FreeBSD level. It should alleviate if not resolve the above errors in the messages log. 

To make this setting persist, please add it to the /flash/nsconfig/rc.netscaler file.

If the error continues to happen with this setting in place,  check storage environment.