Date: Tue, 20 Nov 2007 12:34:01 +0000 From: "Joao Barros" <joao.barros@gmail.com> To: "FreeBSD Questions" <questions@freebsd.org> Subject: Weird %busy in systat Message-ID: <70e8236f0711200434y3694c11auc0bd2e92d17fa44a@mail.gmail.com>
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I'm doing a zpool scrub to exercise my system and noticed one strange
thing when looking at the output of 'systat -vm':
Disks ad0 ad1 ad4 ad6 ar0 ar1
KB/t 44.87 44.71 45.47 45.44 0.00 0.00
tps 162 163 160 162 0 0
MB/s 7.11 7.13 7.11 7.18 0.00 0.00
%busy 100 100 63 62 0 0
where:
ad0: 305245MB <Seagate ST3320620AS 3.AAK> at ata0-master SATA150
ad1: 305245MB <Seagate ST3320620AS 3.AAK> at ata0-slave SATA150
ad4: 305245MB <WDC WD3200KS-00PFB0 21.00M21> at ata2-master SATA150
ad6: 305245MB <Seagate ST3320620AS 3.AAJ> at ata3-master SATA150
are connected to:
atapci0: <Promise PDC20319 SATA150 controller> port
0xb000-0xb03f,0xb400-0xb40f,0xb800-0xb87f mem
0xfc024000-0xfc024fff,0xfc000000-0xfc01ffff irq 23 at device 4.0 on
pci4
atapci1: <Intel 6300ESB SATA150 controller> port
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0xf000-0xf00f irq 18 at device
31.2 on pci0
and my zpool is:
config:
NAME STATE READ WRITE CKSUM
r4x320 ONLINE 0 0 0
raidz1 ONLINE 0 0 0
ad0s1d ONLINE 0 0 0
ad1s1d ONLINE 0 0 0
ad4 ONLINE 0 0 0
ad6 ONLINE 0 0 0
Why is %busy so different when the disks are doing the same thing?
The only difference is the SATA controllers and zfs using a slice on
half of them and a whole disk with the other half.
What is taken into account when calculating %busy? I can go read code
but was hoping for someone with specific knowledge to answer :)
--
Joao Barros
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