Re: Why is NCQ enabled by default by libata? (2.6.20)
From: Justin Piszcz
Date: Tue Mar 27 2007 - 12:26:36 EST
On Tue, 27 Mar 2007, linux@xxxxxxxxxxx wrote:
Here's some more data.
6x ST3400832AS (Seagate 7200.8) 400 GB drives.
3x SiI3232 PCIe SATA controllers
2.2 GHz Athlon 64, 1024k cache (3700+), 2 GB RAM
Linux 2.6.20.4, 64-bit kernel
Tested able to sustain reads at 60 MB/sec/drive simultaneously.
RAID-10 is across 6 drives, first part of drive.
RAID-5 most of the drive, so depending on allocation policies,
may be a bit slower.
The test sequence actually was:
1) raid5ncq
2) raid5noncq
3) raid10noncq
4) raid10ncq
5) raid5ncq
6) raid5noncq
but I rearranged things to make it easier to compare.
Note that NCQ makes writes faster (oh... I have write cacheing turned off;
perhaps I should turn it on and do another round), but no-NCQ seems to have
a read advantage. %$%@#$@#ing bonnie++ overflows and won't print file
read times; I haven't bothered to fix that yet.
NCQ seems to have a pretty significant effect on the file operations,
especially deletes.
Update: added
7) wcache5noncq - RAID 5 with no NCQ but write cache enabled
8) wcache5ncq - RAID 5 with NCQ and write cache enabled
RAID=5, NCQ
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
raid5ncq 7952M 31688 53 34760 10 25327 4 57908 86 167680 13 292.2 0
raid5ncq 7952M 30357 50 34154 10 24876 4 59692 89 165663 13 285.6 0
raid5noncq 7952M 29015 48 31627 9 24263 4 61154 91 185389 14 286.6 0
raid5noncq 7952M 28447 47 31163 9 23306 4 60456 89 198624 15 293.4 0
wcache5ncq 7952M 32433 54 35413 10 26139 4 59898 89 168032 13 303.6 0
wcache5noncq 7952M 31768 53 34597 10 25849 4 61049 90 193351 14 304.8 0
raid10ncq 7952M 54043 89 110804 32 48859 9 58809 87 142140 12 363.8 0
raid10noncq 7952M 48912 81 68428 21 38906 7 57824 87 146030 12 358.2 0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files:max:min /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
16:100000:16/64 1351 25 +++++ +++ 941 3 2887 42 31526 96 382 1
16:100000:16/64 1400 18 +++++ +++ 386 1 4959 69 32118 95 570 2
16:100000:16/64 636 8 +++++ +++ 176 0 1649 23 +++++ +++ 245 1
16:100000:16/64 715 12 +++++ +++ 164 0 156 2 11023 32 2161 8
16:100000:16/64 1291 26 +++++ +++ 2778 10 2424 33 31127 93 483 2
16:100000:16/64 1236 26 +++++ +++ 840 3 2519 37 30366 91 445 2
16:100000:16/64 1714 37 +++++ +++ 1652 6 789 11 4700 14 12264 48
16:100000:16/64 634 11 +++++ +++ 1035 3 338 4 +++++ +++ 1349 5
raid5ncq,7952M,31688,53,34760,10,25327,4,57908,86,167680,13,292.2,0,16:100000:16/64,1351,25,+++++,+++,941,3,2887,42,31526,96,382,1
raid5ncq,7952M,30357,50,34154,10,24876,4,59692,89,165663,13,285.6,0,16:100000:16/64,1400,18,+++++,+++,386,1,4959,69,32118,95,570,2
raid5noncq,7952M,29015,48,31627,9,24263,4,61154,91,185389,14,286.6,0,16:100000:16/64,636,8,+++++,+++,176,0,1649,23,+++++,+++,245,1
raid5noncq,7952M,28447,47,31163,9,23306,4,60456,89,198624,15,293.4,0,16:100000:16/64,715,12,+++++,+++,164,0,156,2,11023,32,2161,8
wcache5ncq,7952M,32433,54,35413,10,26139,4,59898,89,168032,13,303.6,0,16:100000:16/64,1291,26,+++++,+++,2778,10,2424,33,31127,93,483,2
wcache5noncq,7952M,31768,53,34597,10,25849,4,61049,90,193351,14,304.8,0,16:100000:16/64,1236,26,+++++,+++,840,3,2519,37,30366,91,445,2
raid10ncq,7952M,54043,89,110804,32,48859,9,58809,87,142140,12,363.8,0,16:100000:16/64,1714,37,+++++,+++,1652,6,789,11,4700,14,12264,48
raid10noncq,7952M,48912,81,68428,21,38906,7,57824,87,146030,12,358.2,0,16:100000:16/64,634,11,+++++,+++,1035,3,338,4,+++++,+++,1349,5
I would try with write-caching enabled.
Also, the RAID5/RAID10 you mention seems like each volume is on part of
the platter, a strange setup you got there :)
Also you are disabling NCQ on/off via the /sys/block device, e.g., setting
it to 1 (off) and 31 (on) during testing, yes?
Justin.
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