VirtualBox 5.1 - Virtual Disk behaves like it is cached, even though it is not
Posted: 22. Jul 2016, 16:14
Hello,
I wonder if anyone is facing the same issue I do on the VirtualBox 5.1 on linux host.
I have a centos 7.0 VM on a Ubuntu 16.04 LTS host, running VirtualBox 5.1.2r108956 I setup a new 2GB vdi virtualdisk, write-through, fixed-size, with the vdi file sitting in a folder on my host's hard disk and attach it on the vm with the sata controller set not to use host i/o cache. I then start the vm, login in the vm and run fio on the entire 2GB disk, 1 thread, iodepth 1, 4K block size. The results I get from fio are the following:
fio-generator.sh is a script I have authored that makes fio usage simpler. The parameters given are visible in fio's output. This latency and IOPS are not representative of an HD rotational device. This was not the case in VirtualBox 5.0 I want to have devices in my VMs for developing purposes that exhibit rotational hard disks I/O characteristics, and it seems that now I cannot.
I wonder if anyone is facing the same issue I do on the VirtualBox 5.1 on linux host.
I have a centos 7.0 VM on a Ubuntu 16.04 LTS host, running VirtualBox 5.1.2r108956 I setup a new 2GB vdi virtualdisk, write-through, fixed-size, with the vdi file sitting in a folder on my host's hard disk and attach it on the vm with the sata controller set not to use host i/o cache. I then start the vm, login in the vm and run fio on the entire 2GB disk, 1 thread, iodepth 1, 4K block size. The results I get from fio are the following:
Code: Select all
./fio-generator.sh /dev/sdf 1 1 4k 10 randread 8000 0 1
offset=0m
filesize=8000m
thread: (g=0): rw=randread, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=1
fio-2.2.8
Starting 1 process
Jobs: 1 (f=1): [r(1)] [100.0% done] [57924KB/0KB/0KB /s] [14.5K/0/0 iops] [eta 00m:00s]
thread: (groupid=0, jobs=1): err= 0: pid=3919: Fri Jul 22 13:49:05 2016
read : io=587456KB, bw=58740KB/s, iops=14684, runt= 10001msec
slat (usec): min=9, max=701, avg=11.64, stdev= 3.32
clat (usec): min=15, max=4378, avg=55.13, stdev=25.83
lat (usec): min=50, max=4389, avg=66.91, stdev=26.73
clat percentiles (usec):
| 1.00th=[ 43], 5.00th=[ 45], 10.00th=[ 45], 20.00th=[ 47],
| 30.00th=[ 48], 40.00th=[ 50], 50.00th=[ 53], 60.00th=[ 55],
| 70.00th=[ 56], 80.00th=[ 59], 90.00th=[ 65], 95.00th=[ 73],
| 99.00th=[ 97], 99.50th=[ 113], 99.90th=[ 306], 99.95th=[ 422],
| 99.99th=[ 1080]
bw (KB /s): min=56672, max=60192, per=99.95%, avg=58707.37, stdev=945.36
lat (usec) : 20=0.01%, 50=35.78%, 100=63.34%, 250=0.75%, 500=0.09%
lat (usec) : 750=0.01%, 1000=0.01%
lat (msec) : 2=0.01%, 4=0.01%, 10=0.01%
cpu : usr=0.00%, sys=21.54%, ctx=146864, majf=0, minf=32
IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
issued : total=r=146864/w=0/d=0, short=r=0/w=0/d=0, drop=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs):
READ: io=587456KB, aggrb=58739KB/s, minb=58739KB/s, maxb=58739KB/s, mint=10001msec, maxt=10001msec
Disk stats (read/write):
sdf: ios=145391/0, merge=0/0, ticks=9188/0, in_queue=9187, util=91.90%
).