linux-kernel - Re: Why is NCQ enabled by default by libata? (2.6.20)

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Message-ID: <20070327161616.31448.qmail@science.horizon.com>
Date:	27 Mar 2007 12:16:16 -0400
From:	linux@...izon.com
To:	htejun@...il.com, jeff@...zik.org, jpiszcz@...idpixels.com,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	linux@...izon.com
Subject: Re: Why is NCQ enabled by default by libata? (2.6.20)

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.  %$%@#$@...g 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
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