Hi list.
I run a file server on MD raid-5.
If a client reads one big file and at the same time another client tries
to write a file, the thread writing just sits in uninterruptible sleep
until the reader has finished. Only very small amount of writes get
trough while the reader is still working.
I'm having some trouble pinpointing the problem.
It's not consistent either sometimes it works as expected both the
reader and writer gets some transactions. On huge reads I've seen the
writer blocked for 30-40 minutes without any significant writes
happening (Maybe a few megabytes, of several gigs waiting). It happens
with NFS, SMB and FTP, and local with dd. And seems to be connected to
raid-5. This does not happen on block devices without raid-5. I'm also
wondering if it can have anything to do with loop-aes? I use loop-aes on
top of the md, but then again i have not observed this problem on
loop-devices with disk backend. I do know that loop-aes degrades
performance but i didn't think it would do something like this?
I've seen this problem in 2.6.16-2.6.21
All disks in the array is connected to a controller with a SiI 3114 chip.
vmstat while one reader (on gigabit network) is running and one writer
(on gigabit network) is trying it's thing.
# vmstat -n 5
procs -----------memory---------- ---swap-- -----io---- -system--
----cpu----
r b swpd free buff cache si so bi bo in cs us sy
id wa
1 2 152 52664 19952 1137532 0 0 9 6 12 9 7 5
81 6
0 3 152 52640 19896 1138232 0 0 13934 0 1427 1683 1
12 0 87
1 3 152 52572 19908 1138540 0 0 13956 0 1418 1610 1
13 0 86
0 3 152 51668 19820 1139152 0 0 13876 0 1421 1618 2
12 0 86
0 3 152 52176 19812 1138708 0 0 13980 0 1434 1622 1
13 0 86
0 3 152 52744 20068 1144536 0 0 14833 855 1763 2292 2
14 1 83
0 2 152 52600 20356 1138536 0 0 18538 22 2061 2126 1
17 1 81
1 2 152 52624 20748 1137716 0 0 19246 0 1969 2297 1
17 0 81
1 2 152 52720 21140 1136976 0 0 20960 0 2119 2425 4
20 1 74
0 3 152 52876 21792 1136028 0 0 18807 12 1972 2241 1
17 0 82
...
1 3 152 52608 22380 1136296 0 0 12 6 13 9 7 5
81 6
0 2 152 52548 22044 1136296 0 0 16982 0 1739 1993 2
15 0 83
0 3 152 52736 21824 1136440 0 0 18679 0 1838 2215 1
17 1 81
1 3 152 51228 22016 1137536 0 0 15984 14 1615 1974 2
14 1 84
0 3 152 51176 22028 1137964 0 0 16910 8 1717 2016 1
15 0 83
3 2 152 51912 21812 1137352 0 0 18071 1 1792 2106 2
16 1 82
1 2 152 52940 21804 1136376 0 0 15441 1 1586 1916 1
14 0 85
0 3 152 51912 21808 1137368 0 0 16938 0 1653 1967 1
15 1 83
1 3 152 52608 21836 1136108 0 0 17174 13 1683 1920 2
15 0 83
0 3 152 52752 21712 1136092 0 0 16534 0 1640 1890 1
15 1 83
1 2 152 52248 21496 1137328 0 0 16520 2 1640 1757 2
15 0 83
the array:
md0 : active raid5 sdh[0] sdi[7] sdn[6] sdk[5] sdl[4] sdj[3] sdm[2] sdg[1]
3418705472 blocks level 5, 64k chunk, algorithm 2 [8/8] [UUUUUUUU]
iostat snapshot while a writer i blocked:
avg-cpu: %user %nice %system %iowait %steal %idle
0.50 0.00 11.44 86.57 0.00 1.49
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
hdd 0.00 0.00 0.00 0 0
sda 0.00 0.00 0.00 0 0
sdb 0.00 0.00 0.00 0 0
sdc 0.00 0.00 0.00 0 0
sdd 0.00 0.00 0.00 0 0
sde 0.00 0.00 0.00 0 0
sdf 0.00 0.00 0.00 0 0
sdg 28.43 1694.12 0.00 1728 0
sdh 88.24 1847.06 0.00 1884 0
sdi 28.43 1752.94 0.00 1788 0
sdj 27.45 1694.12 0.00 1728 0
sdk 28.43 1756.86 0.00 1792 0
sdl 38.24 1717.65 0.00 1752 0
sdm 52.94 1694.12 0.00 1728 0
sdn 45.10 1733.33 0.00 1768 0
md0 3462.75 13850.98 0.00 14128 0
dm-0 0.00 0.00 0.00 0 0
dm-1 0.00 0.00 0.00 0
One more, some time later:
avg-cpu: %user %nice %system %iowait %steal %idle
2.51 0.00 12.06 85.43 0.00 0.00
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
hdd 0.00 0.00 0.00 0 0
sda 14.14 64.65 0.00 64 0
sdb 0.00 0.00 0.00 0 0
sdc 0.00 0.00 0.00 0 0
sdd 0.00 0.00 0.00 0 0
sde 0.00 0.00 0.00 0 0
sdf 0.00 0.00 0.00 0 0
sdg 26.26 1551.52 0.00 1536 0
sdh 63.64 1672.73 0.00 1656 0
sdi 30.30 1551.52 0.00 1536 0
sdj 30.30 1555.56 0.00 1540 0
sdk 24.24 1551.52 0.00 1536 0
sdl 28.28 1551.52 0.00 1536 0
sdm 35.35 1559.60 0.00 1544 0
sdn 32.32 1551.52 0.00 1536 0
md0 3136.36 12545.45 0.00 12420 0
dm-0 0.00 0.00 0.00 0 0
dm-1 0.00 0.00 0.00 0 0
The hardware should be pretty standard: (lspci)
00:00.0 "Host bridge" "Intel Corporation" "82865G/PE/P DRAM
Controller/Host-Hub Interface" -r02 "Unknown vendor 1919" "Unknown
device 1002"
00:01.0 "PCI bridge" "Intel Corporation" "82865G/PE/P PCI to AGP
Controller" -r02 "" ""
00:03.0 "PCI bridge" "Intel Corporation" "82865G/PE/P PCI to CSA Bridge"
-r02 "" ""
00:1d.0 "USB Controller" "Intel Corporation" "82801EB/ER (ICH5/ICH5R)
USB UHCI Controller #1" -r02 "Unknown vendor 1919" "Unknown device 1002"
00:1d.1 "USB Controller" "Intel Corporation" "82801EB/ER (ICH5/ICH5R)
USB UHCI Controller #2" -r02 "Unknown vendor 1919" "Unknown device 1002"
00:1d.2 "USB Controller" "Intel Corporation" "82801EB/ER (ICH5/ICH5R)
USB UHCI Controller #3" -r02 "Unknown vendor 1919" "Unknown device 1002"
00:1d.3 "USB Controller" "Intel Corporation" "82801EB/ER (ICH5/ICH5R)
USB UHCI Controller #4" -r02 "Unknown vendor 1919" "Unknown device 1002"
00:1d.7 "USB Controller" "Intel Corporation" "82801EB/ER (ICH5/ICH5R)
USB2 EHCI Controller" -r02 -p20 "Unknown vendor 1919" "Unknown device 1002"
00:1e.0 "PCI bridge" "Intel Corporation" "82801 PCI Bridge" -rc2 "" ""
00:1f.0 "ISA bridge" "Intel Corporation" "82801EB/ER (ICH5/ICH5R) LPC
Interface Bridge" -r02 "" ""
00:1f.1 "IDE interface" "Intel Corporation" "82801EB/ER (ICH5/ICH5R) IDE
Controller" -r02 -p8a "Unknown vendor 1919" "Unknown device 1002"
00:1f.2 "IDE interface" "Intel Corporation" "82801EB (ICH5) SATA
Controller" -r02 -p8f "Intel Corporation" "82801EB (ICH5) SATA Controller"
00:1f.3 "SMBus" "Intel Corporation" "82801EB/ER (ICH5/ICH5R) SMBus
Controller" -r02 "Unknown vendor 1919" "Unknown device 1002"
01:00.0 "VGA compatible controller" "nVidia Corporation" "NV5M64 [RIVA
TNT2 Model 64/Model 64 Pro]" -r15 "LeadTek Research Inc." "Unknown
device 2137"
02:01.0 "Ethernet controller" "Intel Corporation" "82547EI Gigabit
Ethernet Controller (LOM)" "Unknown vendor 1919" "Unknown device 1002"
03:03.0 "Mass storage controller" "Silicon Image, Inc." "SiI 3114
[SATALink/SATARaid] Serial ATA Controller" -r02 "Silicon Image, Inc."
"SiI 3114 SATALink Controller"
03:04.0 "FireWire (IEEE 1394)" "VIA Technologies, Inc." "IEEE 1394 Host
Controller" -r80 -p10 "Unknown vendor 1919" "Unknown device 1002"
03:05.0 "RAID bus controller" "Integrated Technology Express, Inc."
"IT/ITE8212 Dual channel ATA RAID controller (PCI version seems to be
IT8212, embedded seems to be ITE8212)" -r11 "Integrated Technology
Express, Inc." "IT/ITE8212 Dual channel ATA RAID controller"
03:09.0 "RAID bus controller" "Silicon Image, Inc." "SiI 3114
[SATALink/SATARaid] Serial ATA Controller" -r02 "Silicon Image, Inc."
"Unknown device 7114"
03:0d.0 "RAID bus controller" "Silicon Image, Inc." "SiI 3114
[SATALink/SATARaid] Serial ATA Controller" -r02 "Silicon Image, Inc."
"SiI 3114 SATARaid Controller"
Thanks for reading.
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