I wanted to see how fast my computer can churn out random numbers, turns out i'm averaging between 3-4 MB as well. This is just local operation, nothing to do with NFS / network.
# cat /dev/urandom >> test.txt
Main Topics
Browse All TopicsI have recently setup a VMware ESX 3.5 environment consisting of two hosts. They have an NFS Datastore that is served up via NFS from a physical Linux server with a RAID 10 of 4 1 TB SATA drives. Each of the VM's (4 total) also connect to an NFS share off of the same RAID 10 (though on a different LVM logical volume). The VM's are all RHEL 5 as well as the NFS server.
I can scp files between VM's at 20-30 MB/s, scp files from the Datastore (VM's local storage) to the NFS mount at 20-30 MB/s and back again at the same speed. I can scp files back and forth to the NFS server directly at 20-30 MB/s. I can dd if=/dev/zero at greater than 100 MB/s to either the Datastore or the NFS mount. However, if I dd if=/dev/urandom it pegs out at a max of roughly 5-6 MB/s. The same occurs with the dd using urandom to an NFS volume on a 0 NetApp filer as well from the same VM's. With the VM that has 4 vCPU's and 24 GB or RAM all of those 20-30's go up to about 60 MB/s but no higher.
It seems that anything actually generating new non-zero data hits a wall.
dd with /dev/zero to NFS mount:
dd if=/dev/zero of=/storage/testfile2 bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 1.17408 seconds, 69.8 MB/s
dd with /dev/zero to Datastore:
dd if=/dev/zero of=/testfile1 bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 0.446165 seconds, 184 MB/s
dd with /dev/urandom to NFS mount:
dd if=/dev/urandom of=/storage/testfile3 bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 16.4113 seconds, 5.0 MB/s
dd with /dev/urandom to Datastore:
dd if=/dev/urandom of=testfile2 bs=8k count=10000
10000+0 records in
10000+0 records out
81920000 bytes (82 MB) copied, 15.3982 seconds, 5.3 MB/s
scp from Datastore to NFS mount:
scp testfile2 XXX.XXX.XXX.XXX:/storage/t
testfile2 100% 78MB 26.0MB/s 00:03
scp from NFS mount to Datastore:
scp XXX.XXX.XXX.XXX:/storage/t
testfile3 100% 78MB 26.0MB/s 00:03
nfsstat -c:
nfsstat -c
Client rpc stats:
calls retrans authrefrsh
143587 0 0
Client nfs v3:
null getattr setattr lookup access readlink
0 0% 7647 5% 34 0% 71439 49% 6473 4% 0 0%
read write create mkdir symlink mknod
1017 0% 45415 31% 35 0% 0 0% 0 0% 0 0%
remove rmdir rename link readdir readdirplus
37 0% 0 0% 0 0% 0 0% 719 0% 10075 7%
fsstat fsinfo pathconf commit
4 0% 396 0% 0 0% 97 0%
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I went back to check to see what I produced doing the same operations as you have in your example and this is what I received (the cpu usage never went below 55% idle and the actual writes were sporadic):
cat /dev/urandom >> test.txt &
iostat -x 1 >> test2.txt (i wasn't sure which device to use at first so i looked at all of them)
avg-cpu: %user %nice %system %iowait %steal %idle
0.42 0.05 0.32 2.18 0.00 97.03
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 15.03 10.50 10.05 1.59 2027.71 96.74 182.46 0.27 23.15 8.04 9.36
sda1 0.03 0.00 0.01 0.00 0.89 0.00 66.83 0.00 8.81 7.17 0.01
sda2 15.00 10.50 10.04 1.59 2026.82 96.74 182.60 0.27 23.17 8.05 9.36
dm-0 0.00 0.00 3.73 10.61 133.60 84.91 15.24 3.42 238.34 2.73 3.91
dm-1 0.00 0.00 0.05 1.02 0.82 8.18 8.42 0.05 47.46 4.89 0.52
dm-2 0.00 0.00 0.14 0.13 1.11 1.08 8.14 0.01 40.55 13.57 0.36
dm-3 0.00 0.00 0.00 0.00 0.01 0.00 8.00 0.00 7.89 0.41 0.00
dm-4 0.00 0.00 21.12 0.32 1891.27 2.57 88.31 0.48 22.52 3.71 7.96
hda 0.00 0.00 0.00 0.00 0.00 0.00 15.20 0.00 1.10 0.90 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.26 0.00 25.77 10.57 0.00 63.40
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 6256.00 0.00 66.00 0.00 50576.00 766.30 13.57 205.64 6.94 45.80
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 6256.00 0.00 66.00 0.00 50576.00 766.30 13.57 205.64 6.94 45.80
dm-0 0.00 0.00 0.00 6320.00 0.00 50560.00 8.00 1447.89 229.10 0.07 44.30
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 2.00 0.00 16.00 8.00 0.03 15.00 7.50 1.50
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.00 0.00 0.00 75.00
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.00 0.00 0.00 75.00
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.13 0.00 0.00 74.87
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.26 0.00 24.74 0.00 0.00 75.00
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.26 8.85 0.00 65.89
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 6231.00 1.00 63.00 8.00 50352.00 786.88 9.71 151.77 5.86 37.50
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 6231.00 1.00 63.00 8.00 50352.00 786.88 9.71 151.77 5.86 37.50
dm-0 0.00 0.00 1.00 6294.00 8.00 50352.00 8.00 1057.40 167.98 0.06 37.50
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.26 0.00 25.06 0.00 0.00 74.68
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.13 0.00 0.00 74.87
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 24.87 0.00 0.00 75.13
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.19 0.00 0.00 74.81
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.45 18.77 0.00 55.78
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 6213.00 0.00 0.00 0.00 0.00 0.00 41.03 0.00 0.00 66.40
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 6213.00 0.00 0.00 0.00 0.00 0.00 41.03 0.00 0.00 66.40
dm-0 0.00 0.00 0.00 6276.00 0.00 50208.00 8.00 4108.36 0.00 0.11 66.40
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 2.00 0.00 16.00 8.00 0.19 0.00 46.50 9.30
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 1.00 0.00 8.00 8.00 0.11 0.00 115.00 11.50
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.00 50.00 0.00 25.00
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 8.00 0.00 5616.00 702.00 66.06 1654.75 125.25 100.20
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 8.00 0.00 5616.00 702.00 66.06 1654.75 125.25 100.20
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6281.44 0.00 0.00 100.20
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 100.20
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 100.20
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.26 0.00 24.87 21.76 0.00 53.11
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 22.00 0.00 62.00 0.00 44824.00 722.97 12.55 1716.11 7.19 44.60
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 22.00 0.00 62.00 0.00 44824.00 722.97 12.55 1716.11 7.19 44.60
dm-0 0.00 0.00 0.00 23.00 0.00 184.00 8.00 1252.93 455718.57 19.35 44.50
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.75 0.00 0.00 37.40
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 3.00 0.00 24.00 8.00 0.48 533.33 143.67 43.10
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 24.94 0.00 0.00 75.06
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
avg-cpu: %user %nice %system %iowait %steal %idle
0.00 0.00 25.00 0.00 0.00 75.00
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
hda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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Answer for Membership
by: oocytePosted on 2009-10-22 at 19:53:17ID: 25641047
It's not an NFS problem, it's actually a limitation on the CPU.
/dev/urandom generate a new random number for every byte you are trying to write.
So, with 5 MB / second, your CPU is literally dying trying to get some air. That's a lot of rand() calls.