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........

I keep reading these drives are slower, but they are cheap and still SSDand work very fast for my needs. As you can see the sequential read is 481-491MB/s, if I put them in MDADM RAID10 mode (normal RAID1) they should give me well over 900MB/s and with redundancy and being very cheap for what they offer. [1232206.315622] scsi 8:0:1:0: Direct-Access ATA ADATA SU800&........

To disable NCQ in the Linux kernel (change sda to match your device). echo 1 > /sys/block/sda/device/queue_depth To enable NCQ (change sda to match your device). echo 31 > /sys/block/sda/device/queue_depth........

[ 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 [........

Another new drive bad from the start: Jun 2 15:14:18 one-desktop kernel: [15895.386779] ata2.00: exception Emask 0x50 SAct 0x1 SErr 0x280900 action 0x6 frozen Jun 2 15:14:18 one-desktop kernel: [15895.386782] ata2.00: irq_stat 0x08000000, interface fatal error Jun 2 15:14:18 one-desktop kernel: [15895.386784] ata2: SError: { UnrecovData HostInt 10B8B BadCRC } Jun 2 15:14:18 one-desktop kernel: [15895.386788] ata2.00: cmd 60/0........

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:........

[ 12.460014] ata1: SRST failed (errno=-16) [ 17.626677] ata1: link is slow to respond, please be patient (ready=0) [ 22.480011] ata1: SRST failed (errno=-16) [ 27.646681] ata1: link is slow to respond, please be patient (ready=0) [ 38.106817] ata1.01: failed to IDENTIFY (INIT_DEV_PARAMS failed, err_mask=0x80) [ 48.266676] ata1: link is slow to respond, please be patient (ready=0)........

I like dd, although it only reads it, usually a read test of the entire disk will uncover if your hard drive is bad in some parts. This is a good thing to do at least once a month, a lot of times bizarre program behavior, laginess and crashing/unnmounting problems etc.. are due to a failing disc and SMART won't know it or indicate a problem: We must also remember there's never a guarantee, I've found that ever since we moved to larger and more platters per drive with 1TB drives........

This happened during a RAID array check: SMART says both drives pass the test, but I'm doing a long test on them and hopefully this is not a hardware error. Apr 3 04:22:01 remote kernel: md: syncing RAID array md2 Apr 3 04:22:01 remote kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc. Apr 3 04:22:01 remote kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction. Apr........

[137392.910057] ata4.00: exception Emask 0x0 SAct 0x1 SErr 0x80000 action 0x6 frozen [137392.910077] ata4: SError: { 10B8B } [137392.910095] ata4.00: cmd 60/20:00:00:00:00/00:00:00:00:00/40 tag 0 ncq 16384 in [137392.910099] res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout) [137392.910122] ata4.00: status: { DRDY } [137392.910135] ata4: hard resetting link [137393.440060] ata4: SATA link........

I separated the 2 drives in the RAID 1 array. 1 is the old one /dev/sda and is out of date, while the separated other one /dev/sdc was in another drive and mounted and used with more data (updated). I wonder how mdadm will handle this: usb-storage: device scan complete md: md127 stopped. md: bind md: md127: raid array is not clean -- starting background reconstruction raid1: raid set md127 active with 1 out of 2 m........

[27969.398749] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB) [27969.398749] sd 5:0:0:0: [sdb] Write Protect is off [27969.398749] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00 [27969.398749] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [27972.117543] ata6.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x0 [27972.117543] ata6.00: irq_stat 0x48000000 [27972.117543] ata6.00: cmd 60/08:00:ff:7........

From the package "parted" you can use the command "partprobe" to re-read the partition table. I really hate rebooting, and that's what Iloved to hear about AHCI motherboards, that they allow hotswap so you don't have to reboot. But that's only as good as the OS, if the OS does not reload the partition table you won't be able to do anything with that new drive you attached without rebooting. Yes, even without re-reading the partiton table Linux will........