Hadoop I/O Analysis

Architects)view)of)Hadoop)I/O)

I/O)analysis)using)vProbes)
)
Richard)McDougall)
V1.0))
April)2012)

Architect’s)QuesFons)
•  Does)Hadoop)really)need)compute)+)data)
local)
•  How)much)and)what)I/O)rates)of)ephemeral)
data)do)we)need)to)design)for?)
•  What)I/O)paKerns)do)we)need)to)support)
HDFS?)
•  What)is)the)I/O)paKern)of)MNR)tasks)
•  Are)there)opportuniFes)for)caching)–)map)
input,)output)or)ephemeral?)

Controlled)Small)Study)
•  Focus)on)developing)tooling)
•  Using)vProbes)+)Perl)+)R)
•  Hadoop)0.20.204)
•  Terasort)@)1GB)
•  One)Namenode,)Tasktracker,)Datanode)

Terasort)
Map)Task)

Map)Task)
Reduce) Output)File)
Input)File) Shuﬄe) (Sort))
Map)Task)

Map)Task)

Input)
Splits) Sort)Chunk)of) Shuﬄe)output)
Combine)and)Sort)
(x16)) Of)KeyNValues) To)Reducers)

Log)of)the)sort)‘Job’)
$ log.pl job_201201261301_0005_1327649126255_rmc_TeraSort !
Item Time Jobname Taskname Phase Start-Time End-Time Elapsed !
Job 0.000 201201261301_0005 !
Job 201201261301_0005 !
Job 0.475 201201261301_0005 PREP !
Task 1.932 201201261301_0005 m_000017 SETUP !
MapAttempt 3.066 201201261301_0005 m_000017 SETUP !
MapAttempt 10.409 201201261301_0005 m_000017 SETUP SUCCESS 1.932 10.409 8.477 "setup"!
Task 10.966 201201261301_0005 m_000017 SETUP SUCCESS 1.932 10.966 9.034 !
Job 201201261301_0005 RUNNING !
Task 10.970 201201261301_0005 m_000000 MAP !
Task 10.972 201201261301_0005 m_000001 MAP !
MapAttempt 10.981 201201261301_0005 m_000000 MAP !
MapAttempt 65.819 201201261301_0005 m_000000 MAP SUCCESS 10.970 65.819 54.849 ""!
Task 68.063 201201261301_0005 m_000000 MAP SUCCESS 10.970 68.063 57.093 !
MapAttempt 10.998 201201261301_0005 m_000001 MAP !
Task 68.066 201201261301_0005 m_000002 MAP !
Task 68.067 201201261301_0005 m_000003 MAP !
Task 68.068 201201261301_0005 r_000000 REDUCE !
MapAttempt 68.075 201201261301_0005 m_000002 MAP !
MapAttempt 68.076 201201261301_0005 m_000003 MAP !
…!
ReduceAttempt 68.112 201201261301_0005 r_000000 REDUCE !
ReduceAttempt 795.299 201201261301_0005 r_000000 REDUCE SUCCESS 68.068 795.299 727.231 "reduce > reduce"!
Task 798.223 201201261301_0005 r_000000 REDUCE SUCCESS 68.068 798.223 730.155 !
Task 798.226 201201261301_0005 m_000016 CLEANUP !
MapAttempt 798.241 201201261301_0005 m_000016 CLEANUP !
MapAttempt 806.113 201201261301_0005 m_000016 CLEANUP SUCCESS 798.226 806.113 7.887 "cleanup"!
Task 807.252 201201261301_0005 m_000016 CLEANUP SUCCESS 798.226 807.252 9.026 !
Job 807.253 201201261301_0005 SUCCESS 0.000 807.253 807.253 !

Terasort:)Map)and)Reduce)Phases)
Setup)Map) Elapsed)Time)N)Seconds)

Mappers)

Reducer)

Cleanup)Map)

Terasort:)Map)and)Reduce)Phases)
Setup)Map) Elapsed)Time)N)Seconds)
Zoom)in)
on)
Map)Task)
I/O)

Mappers)

Zoom)in)
on)
Reduce)
Task)I/O)
Reducer)

Cleanup)Map)

VMware)vProbes)
•  Dynamic)
InstrumentaFon)

•  Probe)mulFple)
VMs)

•  Probe)
VirtualizaFon)
Layer)

•  VMware)Fusion)
and)WorkstaFon)

vProbes)

GUEST:ENTER:system_call {!
string path;!
comm = curprocname();!
tid = curtid();!
pid = curpid();!
ppid = curppid();!
syscall_num = sysnum;!
!
if(syscall_num == NR_open) {!
!path = guestloadstr(sys_arg0);!
syscall_name = "open";!
sprintf(syscall_args, ""%s", %x, %x", path, sys_arg1, sys_arg2); !
…!
}!
!
GUEST:OFFSET:ret_from_sys_call:0 {!
!printf("%s/%d/%d/%d %s(%s) = %d <0>n", comm, pid, rtid, ppid, syscall_name,!
syscall_args, getgpr(REG_RAX)); !
}!
!
!
java/14774/15467/1 open("/host/hadoop/hdfs/data/current/subdir0/blk_1719908349220085071_1649.meta", 0, 1b6) = 144 <0>!
java/14774/15467/1 stat("/host/hadoop/hdfs/data/current/subdir0/blk_1719908349220085071_1649.meta", 7f0b80a4e590) = 0
<0>!
java/14774/15467/1 read(144, 7f0b80a4c470, 4096) = 167 <0>!
!

Pathname)ResoluFon)
filetracevp.pl: !
!
if ($syscall =~ m/open/) {!
$path1 = $line;!
$path1 =~ s/[A-z/0-9]+[ ]+[a-z]+("([^"]+)".*n/1/;!
$fd1 = $line;!
if ($fd1 =~ s/.* ([0-9]+) <.*>n/1/) {!
$fds{$pid,$fd1} = $path1;!
!
if ($syscall =~ m/write/) {!
$params = $line;!
if ($params =~ s/^[A-z/0-9]+[ ]+[a-z]+(([0-9]+),.* ([0-9]+)) = ([0-9]+) <(.*)>n/1,2,3,4/) {!
($fd1, $size, $bytes, $lat) = split(',', $params);!
$path1 = $fds{$pid, $fd1};!
…!
!
!
java,14774,15467,,open,0,0,0,0,144,/host/hadoop/hdfs/data/current/subdir0/blk_1719908349220085071_1649.meta,0,!
java,14774,15467,,stat,0,0,0,0,0,/host/hadoop/hdfs/data/current/subdir0/blk_1719908349220085071_1649.meta,0,!
java,14774,15467,,read,4096,167,0,0,144,/host/hadoop/hdfs/data/current/subdir0/blk_1719908349220085071_1649.meta,0,!
!
!
!
!

Controlled)SmallNScale)Study)
$ hadoop jar hadoop-examples-0.20.204.0.jar teragen 10000000 teradata!
<begin trace>!
$ hadoop jar hadoop-examples-0.20.204.0.jar terasort teradata teraout!
!
Job Counters ! Hadoop)Distro) 236)
Launched reduce tasks=1! Hadoop)Logs) 132)
SLOTS_MILLIS_MAPS=1146887!
Hadoop)clienKmp)unjar) 1)
Launched map tasks=16!
Data-local map tasks=16! Mappers)files)jobcache)N)spills) 1753)
SLOTS_MILLIS_REDUCES=766823! Mappers)files)jobcache)N)output) 1777)
File Input Format Counters ! Reducer)Intermediate) 764)
Bytes Read=1000057358!
Reducers)Shuffle)and)Intermediate) 1744)
File Output Format Counters !
Bytes Written=1000000000! Jobcache)class)files)and)shell)scripts) 1)
FileSystemCounters! Hadoop)Datanode) 1690)
FILE_BYTES_READ=2382257412! JVM)N)/usr/lib/jvm…) 98)
HDFS_BYTES_READ=1000059070!
Total&MB& 7987&
FILE_BYTES_WRITTEN=3402627838!
HDFS_BYTES_WRITTEN=1000000000!
JVM)N)/usr/lib/jvm…)
Map-Reduce Framework!
Map output materialized bytes=1020000096! Hadoop)Datanode)
Map input records=10000000!
Jobcache)class)files)and)shell)scripts)
Reduce shuffle bytes=1020000096!
Spilled Records=33355441! Reducers)files)jobcache)N)output)
Map output bytes=1000000000! Reducer)intermediate)file)
Map input bytes=1000000000!
Combine input records=0! Mappers)files)jobcache)N)map)output)
SPLIT_RAW_BYTES=1712! Mappers)files)jobcache)N)spills)
Reduce input records=10000000!
Reduce input groups=10000000! Hadoop)clienKmp)unjar)
Combine output records=0! Hadoop)Logs)
Reduce output records=10000000!
Hadoop)Distro)
Map output records=10000000!
0) 200) 400) 600) 800)1000)1200)1400)1600)1800)2000)

Hadoop)I/O)Model)
(With)some)data)from)early)observaFons))

Map)Task)
Reduce)
Map)Task)
Job) Map) Reduce) Sort)
Map)Task) Output)
ﬁle.out*
Spills)
Map)Task)

DFS)
Spills)
&)Logs)
) Shuﬄe)
Map_*.out*
Input)
Data)
spill*.out* 75%)of) Combine) DFS)
Intermediate.out* Output)
) Disk)Bandwidth) ) Data)
12%)of) 12%)of)
Bandwidth) Bandwidth)
HDFS)

12)

One)Mapper)Task:)Temp)Data)
path bytes
/host/hadoop/clienttmp/mapred/local/taskTracker/rmc/jobcache/job_201201251035_0001/attempt_201201251035_0001_m_000000_0/output/file.out 67586124
/host/hadoop/clienttmp/mapred/local/taskTracker/rmc/jobcache/job_201201251035_0001/attempt_201201251035_0001_m_000000_0/output/spill1.out 52762519
/usr/lib/jvm/javaD6Dopenjdk/jre/lib/rt.jar 5057763
/home/rmc/untars/hadoopD0.20.204.0/hadoopDcoreD0.20.204.0.jar 895582
/home/rmc/untars/hadoopD0.20.204.0/lib/log4jD1.2.15.jar 82522
/home/rmc/untars/hadoopD0.20.204.0/lib/commonsDlangD2.4.jar 70477
/home/rmc/untars/hadoopD0.20.204.0/lib/commonsDconfigurationD1.6.jar 61007
/usr/lib/x86_64DlinuxDgnu/gconv/gconvDmodules 51772
/host/hadoop/clienttmp/mapred/local/taskTracker/rmc/jobcache/job_201201251035_0001/job.xml 44420
/home/rmc/untars/hadoopD0.20.204.0/lib/commonsDcollectionsD3.2.1.jar 29974
/host/hadoop/clienttmp/mapred/local/taskTracker/rmc/jobcache/job_201201251035_0001/attempt_201201251035_0001_m_000000_0/job.xml 21695
/usr/lib/jvm/javaD6Dopenjdk/jre/lib/amd64/libnio.so 15946
/home/rmc/untars/hadoopD0.20.204.0/conf/coreDsite.xml 11024
/usr/lib/jvm/javaD6Dopenjdk/jre/lib/security/java.security 10081
/proc/self/maps 7523

Number of I/Os

0
10000
20000
30000
40000
50000
60000
1
2
4
8
16
32
64
128
256
512
1024

I/O Size Bucket
2048
4096
8192
16384
32768
65536
131072
I/O)measured)at)syscall)

Number of I/Os
Number of I/Os
0
5000
10000
15000
20000
25000
30000

0
5000
10000
15000
20000
25000
30000

1
1 2
2
4
4
8
8
16
16
32
32
64 64

128 128
256 256
512 512
1024 1024
Write I/O Size Bucket

2048
Read I/O Size Bucket

2048
4096
4096
8192
8192
16384
16384
One)Mapper)Task:)Temp)I/O)Counts)

32768
32768
65536
131072 65536
131072

One)Mapper)Task:)Tmp)Bytes)Transferred)

2.5e+08
6e+07

2.0e+08 5e+07

4e+07
1.5e+08

Bytes
Bytes

3e+07

1.0e+08

2e+07

5.0e+07
1e+07

0.0e+00 0e+00

1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072

I/O Size Bucket I/O Size Bucket

I/O)measured)at)syscall) Logical)I/O)(sequenFal)grouping)of)syscalls))

Number of I/Os

0e+00
1e+05
2e+05
3e+05
4e+05
1
2
4
8
16
32
64
128
256
512
1024

I/O Size Bucket
2048
4096
8192
16384
32768
65536
131072
I/O)measured)at)syscall)

Number of I/Os Number of I/Os
0
50000
100000
150000
200000
250000
300000

0
20000
40000
60000
80000

1 1

2 2

4 4

8 8

16 16
32
32
64
64
128
128
256
256
512
512
1024
1024
Reducer)Task:)Temp)I/O)Counts)


2048

2048
4096
4096
8192
8192
16384
16384
32768
32768
65536
65536
131072
131072

Reducer)Task:)Tmp)Bytes)Transferred)

1.5e+09 5e+08

4e+08

1.0e+09
Bytes

3e+08

Bytes
2e+08
5.0e+08

1e+08

0.0e+00 0e+00
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072

1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608


Datanode)–)Bytes)Transferred)
5e+08 7e+08

6e+08

5e+08
1.5e+09
4e+08

Bytes
4e+08
3e+08

2e+08

1e+08
1.0e+09
Bytes

3e+08
Bytes

0e+00

1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072

1e+09

5.0e+08 8e+08

2e+08
6e+08

Bytes
4e+08

1e+08
0.0e+00
2e+08
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072

0e+00
I/O Size Bucket
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072

0e+00

Datanode)–)Actual)vs.)Logical)I/O)Size)
5e+08

5e+08

1.5e+09

4e+08 4e+08

1.0e+09 3e+08

Bytes
Bytes

3e+08
Bytes

2e+08

5.0e+08

1e+08

2e+08
0.0e+00 0e+00 1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072


1e+08

0e+00

Number of I/Os

0
5000
10000
15000
20000
25000
Bytes

0e+00
1e+08
2e+08
3e+08
4e+08
5e+08
1
2
4
8
16
32
64
128
256
512
1024

I/O Size Bucket
2048
4096
8192
16384
32768
65536
131072

Number of I/Os Number of I/Os

0
5000
10000
15000
0
2000
4000
6000
8000
10000

1 1
2 2
4 4
8 8
Datanode)–)IOPS)

16 16
32 32
64 64
128 128
256 256
512 512
1024 1024

2048 2048
4096 4096
8192 8192
16384 16384
32768 32768
65536 65536
131072 131072

Back)of)the)Envelope)Modeling)))
•  How)much)bandwidth)does)terasort)need?)
–  10)seconds)of)CPU/core)Fme)per)task)
–  128MB)of)HDFS)per)task)
–  ~3x,)384MB)of)temporary)data)per)task)

I/O&Component& Per7task& Per7task&Bandwidth& Per7host&(24&
cores)&
HDFS)I/O) 128MB) ~13MBytes/s) 312Mbytes/sec)
Temp) 384MB) ~38Mbytes/sec) 912Mbytes/sec)

Do)we)need)locality?)
•  Main)issue)is)crossNsecFonal)bandwidth)
–  Secondary)issue)is)perNhost)link)speed)
–  Just)look)at)storage)I/O)now,)consider)shuﬄe)next)
I/O& Per7host&(24& Network& Rack&
Component& cores)& Bandwidth&& Bandwidth&
w/&0%&locality& w/40&hosts&
HDFS)I/O) 312Mbytes/sec) 2.5Gbits) 100gbits)
Temp) 912Mbytes/sec) 7.3Gbits) 300gbits)

•  Possible)Conclusion)
–  Must)have)locality)w/1Gbit)host)link)
–  Feasible)to)have)remote)data)w/10Gbit)and)keeping)
temp)local)only)

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