[Gluster-users] VMs blocked for more than 120 seconds

Mon May 20 10:07:54 UTC 2019

Hi Krutika,

> Also, gluster version please?

I am running old 3.7.6. (Yes I know I should upgrade asap)

I’ve applied firstly "network.remote-dio off", behaviour did not changed, VMs got stuck after some time again.
Then I’ve set "performance.strict-o-direct on" and problem completly disappeared. No more stucks at all (7 days without any problems at all). This SOLVED the issue.

Can you explain what remote-dio and strict-o-direct variables changed in behaviour of my Gluster? It would be great for later archive/users to understand what and why this solved my issue.

Anyway, Thanks a LOT!!!

BR, 
Martin

> On 13 May 2019, at 10:20, Krutika Dhananjay <kdhananj at redhat.com> wrote:
> 
> OK. In that case, can you check if the following two changes help:
> 
> # gluster volume set $VOL network.remote-dio off
> # gluster volume set $VOL performance.strict-o-direct on
> 
> preferably one option changed at a time, its impact tested and then the next change applied and tested.
> 
> Also, gluster version please?
> 
> -Krutika
> 
> On Mon, May 13, 2019 at 1:02 PM Martin Toth <snowmailer at gmail.com <mailto:snowmailer at gmail.com>> wrote:
> Cache in qemu is none. That should be correct. This is full command :
> 
> /usr/bin/qemu-system-x86_64 -name one-312 -S -machine pc-i440fx-xenial,accel=kvm,usb=off -m 4096 -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 -uuid e95a774e-a594-4e98-b141-9f30a3f848c1 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-one-312/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime -no-shutdown -boot order=c,menu=on,splash-time=3000,strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 
> 
> -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x4
> -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5
> -drive file=/var/lib/one//datastores/116/312/disk.0,format=raw,if=none,id=drive-virtio-disk1,cache=none
> 	-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk1,id=virtio-disk1
> -drive file=gluster://localhost:24007/imagestore/ <>7b64d6757acc47a39503f68731f89b8e,format=qcow2,if=none,id=drive-scsi0-0-0-0,cache=none
> 	-device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0
> -drive file=/var/lib/one//datastores/116/312/disk.1,format=raw,if=none,id=drive-ide0-0-0,readonly=on
> 	-device ide-cd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0
> 
> -netdev tap,fd=26,id=hostnet0 -device e1000,netdev=hostnet0,id=net0,mac=02:00:5c:f0:e4:39,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/channel/target/domain-one-312/org.qemu.guest_agent.0,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -vnc 0.0.0.0:312 <http://0.0.0.0:312/>,password -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -msg timestamp=on
> 
> I’ve highlighted disks. First is VM context disk - Fuse used, second is SDA (OS is installed here) - libgfapi used, third is SWAP - Fuse used.
> 
> Krutika,
> I will start profiling on Gluster Volumes and wait for next VM to fail. Than I will attach/send profiling info after some VM will be failed. I suppose this is correct profiling strategy.
> 
> About this, how many vms do you need to recreate it? A single vm? Or multiple vms doing IO in parallel?
> 
> 
> Thanks,
> BR!
> Martin
> 
>> On 13 May 2019, at 09:21, Krutika Dhananjay <kdhananj at redhat.com <mailto:kdhananj at redhat.com>> wrote:
>> 
>> Also, what's the caching policy that qemu is using on the affected vms?
>> Is it cache=none? Or something else? You can get this information in the command line of qemu-kvm process corresponding to your vm in the ps output.
>> 
>> -Krutika
>> 
>> On Mon, May 13, 2019 at 12:49 PM Krutika Dhananjay <kdhananj at redhat.com <mailto:kdhananj at redhat.com>> wrote:
>> What version of gluster are you using?
>> Also, can you capture and share volume-profile output for a run where you manage to recreate this issue?
>> https://docs.gluster.org/en/v3/Administrator%20Guide/Monitoring%20Workload/#running-glusterfs-volume-profile-command <https://docs.gluster.org/en/v3/Administrator%20Guide/Monitoring%20Workload/#running-glusterfs-volume-profile-command>
>> Let me know if you have any questions.
>> 
>> -Krutika
>> 
>> On Mon, May 13, 2019 at 12:34 PM Martin Toth <snowmailer at gmail.com <mailto:snowmailer at gmail.com>> wrote:
>> Hi,
>> 
>> there is no healing operation, not peer disconnects, no readonly filesystem. Yes, storage is slow and unavailable for 120 seconds, but why, its SSD with 10G, performance is good.
>> 
>> > you'd have it's log on qemu's standard output,
>> 
>> If you mean /var/log/libvirt/qemu/vm.log there is nothing. I am looking for problem for more than month, tried everything. Can’t find anything. Any more clues or leads?
>> 
>> BR,
>> Martin
>> 
>> > On 13 May 2019, at 08:55, lemonnierk at ulrar.net <mailto:lemonnierk at ulrar.net> wrote:
>> > 
>> > On Mon, May 13, 2019 at 08:47:45AM +0200, Martin Toth wrote:
>> >> Hi all,
>> > 
>> > Hi
>> > 
>> >> 
>> >> I am running replica 3 on SSDs with 10G networking, everything works OK but VMs stored in Gluster volume occasionally freeze with “Task XY blocked for more than 120 seconds”.
>> >> Only solution is to poweroff (hard) VM and than boot it up again. I am unable to SSH and also login with console, its stuck probably on some disk operation. No error/warning logs or messages are store in VMs logs.
>> >> 
>> > 
>> > As far as I know this should be unrelated, I get this during heals
>> > without any freezes, it just means the storage is slow I think.
>> > 
>> >> KVM/Libvirt(qemu) using libgfapi and fuse mount to access VM disks on replica volume. Can someone advice  how to debug this problem or what can cause these issues? 
>> >> It’s really annoying, I’ve tried to google everything but nothing came up. I’ve tried changing virtio-scsi-pci to virtio-blk-pci disk drivers, but its not related.
>> >> 
>> > 
>> > Any chance your gluster goes readonly ? Have you checked your gluster
>> > logs to see if maybe they lose each other some times ?
>> > /var/log/glusterfs
>> > 
>> > For libgfapi accesses you'd have it's log on qemu's standard output,
>> > that might contain the actual error at the time of the freez.
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>> 
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