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Confusion about load bursts on one KVM VPS
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Confusion about load bursts on one KVM VPS

fanfan Veteran
edited January 2012 in General

I've met a weird problem with one of my KVM VPS, the load bursts every few hours, and the problem is, it is mostly idle as a storage box. I've monitored by the OpenStatus and got a really long list of warnings in 14 days, see pic: http://i.minus.com/ibx6GdLIaxVxRU.png, and for comparison, this is a hostigation box with 34 days of uptime: http://i.minus.com/ib27zTHf6vk0sR.png. The VPS has access to 1 CPU core.

The disk benchmark is:

dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync && rm test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 84.5232 s, 12.7 MB/s

hdparm -tT /dev/sda1

/dev/sda1:
Timing cached reads: 18906 MB in 1.99 seconds = 9477.94 MB/sec
Timing buffered disk reads: 182 MB in 3.02 seconds = 60.36 MB/sec

From the conversation with the provider I was told the fault is with the VPS itself since it's KVM so I won't get affected by others sharing the place. Since I'm still not clear about what exactly to blame for this, I'm not going to tell this provider's name this time.

Should I keep on submitting tickets regarding this or fix this by myself?

Comments

  • FranciscoFrancisco Top Host, Host Rep, Veteran

    You're using /dev/sda which means no virtio which could be causing some of our disk slow downs.

    Ask your host to enable it/or enable it in the panel?

    Francisco

  • fanfan Veteran

    @Francisco said: You're using /dev/sda which means no virtio which could be causing some of our disk slow downs.

    Ask your host to enable it/or enable it in the panel?

    Thanks fran, I've asked the same and he said they're using virtual SCSI drives instead as virtio gets obsolete with QEMU 1.0. The dd result was over 100mb/s in the past but no longer.

    Something off topic, will you bring some kvm stock anytime soon? I wish to get a 256 kvm as a tiny remote desktop.

  • FranciscoFrancisco Top Host, Host Rep, Veteran

    Uh, virtio isn't going away.....

    QEMU 1.0 is out and it's alive and well in it so whoever told you that is smoking crack. In fact, there's a new virtio setup being developed that works with VIRTIO + SCSI commands to speed it up and make it all around better.

    SCSI support in KVM is 'ok'. It's not bad but by no means as fast as virtio in our own tests. We've run tests with both the guest and the HN running the latest 3.1.x linux kernels and virtio is always faster by a fairly large margin.

    There will be stock :)

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