SATA 3 disk being driven at 3Gbps rather than 6.
|
| Author | Content |
|---|---|
| Bob_Robertson Apr 04, 2013 9:26 AM EDT |
So, inspired by this article, I did some poking (ok, peeking really): $ dmesg | grep -i sata ... [ 4.528764] ata2: SATA link up 6.0 Gbps (SStatus 133 SControl 300) [ 4.528784] ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300) Right. One DVD drive, one rather gnarly HD. Yet this is just the boot. What about the running status? As suggested in the comments.... $ cat /sys/class/ata_link/link?/sata_spd 1.5 Gbps 3.0 Gbps Would I be correct that my SATA-3 disk is being driven at SATA-2 speeds? |
| penguinist Apr 04, 2013 10:07 AM EDT |
I am seeing a similar discrepancy on my ultrabook's ssd drive. dmesg | grep -i sata shows 6.0 Gbps cat sata_spd shows 3.0 Gbps Since both of those information sources originate from the same source (kernel), I would expect the information to be consistent. I am not sure how to interpret the apparent discrepancy. Any kernel hackers reading this thread? |
| theboomboomcars Apr 04, 2013 10:44 PM EDT |
I got the same thing from the dmesg and cat commands. I tried hdparm -tT /dev/sda and got:
/dev/sda:
Timing cached reads: 19816 MB in 2.00 seconds = 9920.16 MB/sec
Timing buffered disk reads: 796 MB in 3.00 seconds = 265.13 MB/sec The 265 MBs seems to fit in with the SATA 2 speed. It does appear that the SATA 3 devices are being held back or something. |
| BernardSwiss Apr 05, 2013 1:44 AM EDT |
What's actually being identified -- the devices, or the controllers? |
| gus3 Apr 05, 2013 4:17 PM EDT |
Also, check that Native Command Queueing (NCQ) is enabled or disabled. If it's disabled on boot, chances are you have a blacklisted (buggy) chipset. |
| Bob_Robertson Apr 08, 2013 8:48 AM EDT |
Gus, do you have a quick and dirty command to do that, or should I look it up? :^) Interesting: $ cat /sys/block/sda/device/queue_depth 31 |
| gus3 Apr 08, 2013 4:14 PM EDT |
That's a good start. I did: $ dmesg | grep NCQ to find out my chipset's NCQ support was buggy, therefore disabled. |
| Bob_Robertson Apr 08, 2013 4:44 PM EDT |
Gus, How did doing that tell you the chipset was buggy? $ dmesg | grep NCQ [ 4.530851] ata2.00: 976773168 sectors, multi 16: LBA48 NCQ (depth 31/32), AA |
| gus3 Apr 08, 2013 4:49 PM EDT |
It told me NCQ was disabled. My chipset is blacklisted as "buggy" in the source code. I tried removing it from the blacklist, and NCQ became enabled, but the performance difference wasn't worth the risk of massive data loss. |
| Bob_Robertson Apr 08, 2013 4:53 PM EDT |
Ok. I just haven't seen any comparison to know what NCQ "bad" looks like. I should log into my friend's system in California... or not.. :^) |
Posting in this forum is limited to members of the group: [ForumMods, SITEADMINS, MEMBERS.]
Becoming a member of LXer is easy and free. Join Us!