You might assume you have a bad drive or the SATA interface/cable is bad, or the power supply is bad/weak to the drive. These are all possible issues, but definitely check your SATA cable for "twisting". It is a big issue because until the error stops or times out, your system will not boot (in my case this was the case even though the drive with the issue was not part of the OS or booting process at all). If you run an open rig that you move around often that ha........

This is the closest way to disabling it without using the "libata.force=noncq" kernel boot option is to set the queue to a depth of 1 which doesn't actually disable it. Change the sdc below to match the device you want to disable NCQ for. [root@officebox ~]# echo "1" > /sys/block/sdc/device/queue_depth Errors that indicate you are having a performance issue are these in messages or dmesg relating to N........

[ 2868.041375] ata1: EH in SWNCQ mode,QC:qc_active 0x40 sactive 0x40 [ 2868.041554] ata1: SWNCQ:qc_active 0x40 defer_bits 0x0 last_issue_tag 0x6 [ 2868.041556] dhfis 0x40 dmafis 0x40 sdbfis 0x20 [ 2868.041874] ata1: ATA_REG 0x41 ERR_REG 0x84 [ 2868.042013] ata1: tag : dhfis dmafis sdbfis sactive [ 2868.042163] ata1: tag 0x6: 1 1 0 1 [ 2868.042301] ata1.00: exception Emask 0x1 SAct 0x40 SErr 0x400000 action 0x6 frozen [........

This is just trying to read 5GB off the drive with dd and the drive initially tested ok but shortly after I wondered why I was seeing 2MB/s read speeds. Notice the "current_pending_sector", anytime I've seen it at anything above 0 even with no other bad fields/attributes, it means the drive is bad. ata1.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0 ata1.00: irq_stat 0x40000008 ata1.00: failed command: READ FPDMA QUEUED ata1.00: cmd 60/00:00:........

Here's a proven example of what a bad hard drive can do, it was technically functioning OKin a RAID array but the system became extremely low and the load become high and IOWAIT was even higher and I always thought it was a bad application. The truth is that this failing 1TBHitachi has slowly gotten worse and caused huge slowdowns, (eg. 100% load on Thunderbird waiting for e-mails to load etc..). After swapping it out, tabs change instantly, emails are not lagged, and........