On 27/07/2015 6:54 PM, Donny Davis wrote:
Add this on to your dd command
conv=sync
On the console login of my host/server, the 'dd' command I used was:
dd bs=1M count=256 if=/dev/zero of=test conv=fdatasync
Would I be replacing the 'conv=fdatasync' with the 'conv=sync', or am I
appending it (i.e., 'conv=fdatasync,sync')
And then report result. Its no surprise that your writes are slow in raid1
I will give it a try and report results when I re-install my
oVirt+Hosted Engine on my host, however it actually, wasn't/isn't the
write speed on the bare metal host that I was too concerned with but
rather the poor write speed within the guest VMs, particularly my
Windows 7 guest.
As you can see from my original results, within the Win7 guest on oVirt
I was only getting about 10 MByte/s while the host I was able to get
about 74 MByte/s. That just seems like one heck of a performance
drop-off to me, which means I either don't have something
configured/tuned properly, or virtio-SCSI is not that good (though
everything I have rad suggests that virtio-SCSI is what I should be
using for best performance, as long as the guest drivers are installed)
-Alan
Hello,
I am running oVirt 3.5 on a single server (hosted engine). I have two
Western Digital WD20EZRX drives in a hardware RAID1 configuration. My
storage is actually on the single server, but I am attaching to it via NFS.
I created a Windows 7 guest, and I am finding its write speeds to be
horrible. It is a VirtIO-SCSI drive and the guest additions are installed.
The installation of the OS took way longer than bare metal or even
VMware. When I ran Windows updates, it again took a *lot* longer than
on bar metal or on VMware.
The read speeds seem to be fine. The guest is responsive when I click
on programs and they open about as fast as bare metal or VMware.
I downloaded and ran "Parkdale" HDD tester and ran a test with the
following settings:
- File size: 4000
- Block Size: 1 MByte
The results are as follows:
- Seq. Write Speed: 10.7 MByte/sec (Random Q32D: )
- Seq. Read Speed: 237.3 MByte/sec (Random Q32D: )
I ran another test, but this time changing the "Block Size" to "64 kByte
[Windows Default]". Results are as follows:
- Seq. Write Speed: 10.7 MByte/sec (Random Q32D: )
- Seq. Read Speed: 237.3 MByte/sec (Random Q32D: )
On the host, running '|dd bs=1M count=256 if=/dev/zero of=test
conv=fdatasync|' on my data mount via NFS rsuled in the following:
256+0 records in
256+0 records out
268435456 bytes (268 MB) copied, 3.59431 s, 74.7 MB/s
I got this <https://romanrm.net/dd-benchmark>
<https://romanrm.net/dd-benchmark> and measures the write speed of a
disk. As you can see, it is significantly higher than what I am getting
in the Windows guest VM.
Running that same "dd" test on an Ubuntu guest VM gives me 24MB/s.
Any ideas why I have such poor write performance? Is this normal with
oVirt guests? Any ideas on what I might be able to do to improve them?
I don't expect to get close to the "bare metal" results, but maybe
something in the 40-60 MB/s range would be nice.
Thanks, in advance, for your help and advice.
-Alan
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