Eu não usei este ajuste antes, mas você provavelmente quer ajustar o eh_timeout (tratamento de erros timeout) para o disco em questão:
[root@localhost device]# cat /sys/block/sda/device/eh_timeout
10
[root@localhost device]#
O acima mostra sda
definido para 10 segundos. Do Red Hat Knowledgebase:
In certain storage configurations (for example, configurations with many LUNs), the SCSI error handling code can spend a large amount of time issuing commands such as TEST UNIT READY to unresponsive storage devices. A new sysfs parameter, eh_timeout, has been added to the SCSI device object, which allows configuration of the timeout value for TEST UNIT READY and REQUEST SENSE commands used by the SCSI error handling code. This decreases the amount of time spent checking these unresponsive devices. The default value of eh_timeout is 10 seconds, which was the timeout value used prior to adding this functionality.