Geom stripe bottleneck
Frank Broniewski
brfr at metrico.lu
Tue Jun 3 09:56:22 UTC 2014
Hi all,
I have a stripe (RAID0) geom setup for my database's data. Currently I
am applying some large updates on the data and I think the performance
of my stripe could be better. But I am uncertain and so I thought I'd
request some interpretation help from the community :)
The stripe consists of two disks (WD Velociraptor with 10.000 rpm):
>diskinfo -v ada2
ada2
512 # sectorsize
600127266816 # mediasize in bytes (558G)
1172123568 # mediasize in sectors
0 # stripesize
0 # stripeoffset
1162821 # Cylinders according to firmware.
16 # Heads according to firmware.
63 # Sectors according to firmware.
WD-WXH1E61ASNX9 # Disk ident.
and /var/log/dmesg.boot
# snip
ada2 at ahcich2 bus 0 scbus2 target 0 lun 0
ada2: <WDC WD6000HLHX-01JJPV0 04.05G04> ATA-8 SATA 3.x device
ada2: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
ada2: Command Queueing enabled
ada2: 572325MB (1172123568 512 byte sectors: 16H 63S/T 16383C)
ada2: Previously was known as ad8
ada3 at ahcich3 bus 0 scbus3 target 0 lun 0
ada3: <WDC WD6000HLHX-01JJPV0 04.05G04> ATA-8 SATA 3.x device
ada3: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
ada3: Command Queueing enabled
ada3: 572325MB (1172123568 512 byte sectors: 16H 63S/T 16383C)
ada3: Previously was known as ad10
#snap
And here's some iostat -d -w 10 ada0 ada1 ada2 ada3 example output
#snip
ada0 ada1 ada2 ada3
KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s
0.00 0 0.00 0.00 0 0.00 19.33 176 3.32 19.33 176 3.32
16.25 0 0.01 16.25 0 0.01 16.87 133 2.20 16.87 133 2.20
0.00 0 0.00 0.00 0 0.00 16.77 146 2.40 16.77 147 2.40
0.00 0 0.00 0.00 0 0.00 19.46 170 3.24 19.45 170 3.23
21.50 0 0.01 21.50 0 0.01 17.00 125 2.08 17.00 125 2.08
0.50 0 0.00 0.50 0 0.00 16.88 145 2.38 16.88 145 2.38
0.00 0 0.00 0.00 0 0.00 16.96 125 2.07 16.97 125 2.07
0.00 0 0.00 0.00 0 0.00 19.82 158 3.06 19.81 158 3.07
28.77 1 0.03 28.77 1 0.03 16.83 133 2.19 16.82 133 2.19
#snap
I think the MB/s output is rather low for such a disk. To gain further
insight I started gstat:
dT: 1.001s w: 1.000s
L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name
0 27 0 0 0.0 27 2226 4.8 7.0| ada0
0 28 1 32 23.9 27 2226 1.3 3.9| ada1
2 120 115 1838 6.4 5 96 0.2 74.3| ada2
2 121 116 1854 6.3 5 96 0.4 72.9| ada3
0 28 1 32 24.0 27 2226 5.0 8.7| mirror/gm
2 121 116 3708 7.9 5 192 0.4 92.2| stripe/gs
0 28 1 32 24.0 27 2226 5.0 8.7| mirror/gms1
0 12 0 0 0.0 12 1343 9.1 6.9| mirror/gms1a
0 0 0 0 0.0 0 0 0.0 0.0| mirror/gms1b
0 0 0 0 0.0 0 0 0.0 0.0| mirror/gms1d
0 0 0 0 0.0 0 0 0.0 0.0| mirror/gms1e
0 16 1 32 24.0 15 883 1.7 2.9| mirror/gms1f
What bothers me here is that the stripe/gs is 92% busy while the disks
themselves are only at 74/72%. This lead me to my post here and seek
some advice, since I don't know enough about the mechanics and so I
can't really find the problem, if there is any at all.
Btw, here's the output from geom stripe list:
# geom stripe list
Geom name: gs
State: UP
Status: Total=2, Online=2
Type: AUTOMATIC
Stripesize: 8192
ID: 1042782665
Providers:
1. Name: stripe/gs
Mediasize: 1200254517248 (1.1T)
Sectorsize: 512
Stripesize: 8192
Stripeoffset: 0
Mode: r1w1e1
Consumers:
1. Name: ada2
Mediasize: 600127266816 (558G)
Sectorsize: 512
Mode: r1w1e2
Number: 0
2. Name: ada3
Mediasize: 600127266816 (558G)
Sectorsize: 512
Mode: r1w1e2
Number: 1
So is there some bottleneck or I am just worrying about nothing?
Many thanks,
Frank
--
Frank BRONIEWSKI
METRICO s.à r.l.
géomètres
technologies d'information géographique
rue des Romains 36
L-5433 NIEDERDONVEN
tél.: +352 26 74 94 - 28
fax.: +352 26 74 94 99
http://www.metrico.lu
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