Testing ZFS with XCP-ng

olivierlambert

Maybe because it wasn't triggered without a VDI live migration?

borzel

~~did no livemigration ...just local copy of a vm~~
... ah, I should read before I answer ...

borzel

~~@nraynaud Is there any info how to build blktap2 myself to test with my homelab?~~
I did find it here: https://xcp-ng.org/forum/topic/122/how-to-build-blktap-from-sources/3

borzel

I tested the updated version of blktap and build it like described in https://xcp-ng.org/forum/post/1677, but copying a vm within the SR fails

Async.VM.copy R:f286a572f8aa|xapi] Error in safe_clone_disks: Server_error(VDI_COPY_FAILED, [ End_of_file ])

borzel

the function safe_clone_disks is located in https://github.com/xapi-project/xen-api/blob/72a9a2d6826e9e39d30fab0d6420de6a0dcc0dc5/ocaml/xapi/xapi_vm_clone.ml#L139

it calls clone_single_vdi in https://github.com/xapi-project/xen-api/blob/72a9a2d6826e9e39d30fab0d6420de6a0dcc0dc5/ocaml/xapi/xapi_vm_clone.ml#L116

which calls Client.Async.VDI.copy from a XAPI-OCaml Module Client which I can not find

borzel

found something in /var/log/SMlog

Jul 21 19:52:40 xen SM: [17060] result: {'o_direct_reason': 'SR_NOT_SUPPORTED', 'params': '/dev/sm/backend
/4c8bc619-98bd-9342-85fe-1ea4782c0cf2/8e901c80-0ead-4764-b3d9-b04b4376e4c4',
'o_direct': True, 'xenstore_data': {'scsi/0x12/0x80': 'AIAAEjhlOTAxYzgwLTBlYWQtNDcgIA==', 'scsi/0x12/0x83': 
'AIMAMQIBAC1YRU5TUkMgIDhlOTAxYzgwLTBlYWQtNDc2NC1iM2Q5LWIwNGI0Mzc2ZTRjNCA=', 'vdi-uuid': 
'8e901c80-0ead-4764-b3d9-b04b4376e4c4', 'mem-pool': '4c8bc619-98bd-9342-85fe-1ea4782c0cf2'}}

Note the 'o_direct': True in this log entry. But I created the SR with other-config:o_direct=false

stormi

@borzel I'll let @nraynaud have a say, but first, to be sure, you built it with

xcp-build --build-local . --define 'xcp_ng_section extras'

and the resulting RPM contains .extras in its name?

borzel

yes, I did Checked it multiple times. Will check it again today to be 100% sure.

I also saw the right logoutput from @nraynaud new function where he probes the open with O_DIRECT and retries with O_DSYNC.

I have the "feel" that xapi or blktap copy's files in some situations without it's normal way. Maybe a special "file copy" without a open command?

Can I attach a debugger to blktap while in operration? This would also be needed for deep support of the whole server.

stormi

You can probably attach gdb to a running blktap, yes. Install the blktap-debuginfo package that was produced when you built blktap to make debug symbols available.

nraynaud

@borzel there is something fishy around here https://github.com/xapi-project/sm/blob/master/drivers/blktap2.py#L994 I am still unsure what to do.

I have not removed O_DIRECT everywhere in blktap, I was expecting to remove the remainder by the o_direct flag in python, but I guess I was wrong. we might patch the python.

borzel

Maybe we can create a new SR type "zfs" and copy the file SR implementation from https://github.com/xapi-project/sm/blob/master/drivers/FileSR.py
This would us later allow to create a more deeper integration of ZFS.

borzel

Success! I changed in /opt/xensource/sm/blktap2.py

 elif not ((self.target.vdi.sr.handles("nfs") or self.target.vdi.sr.handles("ext") or self.target.vdi.sr.handles("smb"))):

to

 elif not ((self.target.vdi.sr.handles("file")) or (self.target.vdi.sr.handles("nfs") or self.target.vdi.sr.handles("ext") or self.target.vdi.sr.handles("smb"))):

Than I deleted /opt/xensource/sm/blktap2.pyc and /opt/xensource/sm/blktap2.pyo so that the *.py file is used.

Now I can copy from other SR types to my ZFS SR.

But copy within my ZFS SR does not work...

borzel

some info about the o_direct flag: https://xenserver.org/blog/entry/read-caching.html

borzel

After reading some, I think we can not get it fully working in short time. Some of the tools might not work without o_direct support:

If the underlying file-system does not support O_DIRECT, utilities (e.g, vhd-util) may fail with error code 22 (EINVAL). Similarly, Xen may fail with a message as follows:
TapdiskException: ('create', '-avhd:/home/cklein/vms/vm-rubis-0/root.vhd') failed (5632 )

https://github.com/xapi-project/blktap/blob/master/README

Today there is just one fully working local ZFS configuration:

create your ZFS-Pool: zpool create ...
create a ZVOL (aka blockdevice): zfs create -V 50G pool/my_local_sr
create an EXT3 based SR: xe sr-create host-uuid=<UUID_of_your_host> type=ext shared=false name-label=<Name_of_my_SR> device-config:device=/dev/zvol/<pool-name>/<zvol-name>

It's not optimal, but working.

nraynaud

I am working on the issue right now. I am trying to exactly nail the problem.
there are 2 cases:

xe vdi-copy from another SR to a ZFS SR doesn't work
xe vdi-copy on the same SR doesn't work.

I that a complete assessment of the issues you found?

A cursory test seems to show that ssh ${XCP_HOST_UNDER_TEST} sed -i.bak 's/# unbuffered = true/unbuffered = false/' /etc/sparse_dd.conf solves the issue of intra-ZFS copies, but I am still confirming that I have not done anything else on my test box.

Thanks,
Nicolas.

borzel

@nraynaud said in Testing ZFS with XCP-ng:

xe vdi-copy from another SR to a ZFS SR doesn't work
xe vdi-copy on the same SR doesn't work.

Yes

Additional to that the copy from ZFS SR to another SR is not working.

nraynaud

ok, I really think changing /etc/sparse_dd.conf is the right path.

#!/usr/bin/env bash

# HOW TO create the passthrough: xe sr-create name-label="sda passthrough" name-description="Block devices" type=udev content-type=disk device-config:location=/dev/sda host-uuid=77b3f6ad-020b-4e48-b090-74b2a26c4f69

set -ex

MASTER_HOST=root@192.168.100.1
PASSTHROUGH_VDI=a74d267e-bb14-4732-bd80-b9c445199e8a

SNAPSHOT_UUID=19d3758e-eb21-f237-b8f7-6e2f638cc8e0
VM_HOST_UNDER_TEST_UUID=13ec74c2-9b57-a327-962f-1ebd9702eec4
XCP_HOST_UNDER_TEST_UUID=05c61e28-11cf-4131-b645-a0be7637c044
XCP_HOST_UNDER_TEST_IP=192.168.100.151
XCP_HOST_UNDER_TEST=root@${XCP_HOST_UNDER_TEST_IP}

INCEPTION_VM_UUID=a7e37541-fb9a-4392-6b54-60cf7ce3d08a
INCEPTION_VM_IP=192.168.100.32
INCEPTION_VM=root@${INCEPTION_VM_IP}

ssh ${MASTER_HOST} xe snapshot-revert snapshot-uuid=${SNAPSHOT_UUID}
NEW_VBD=`ssh ${MASTER_HOST} xe vbd-create device=1 type=Disk mode=RW vm-uuid=${VM_HOST_UNDER_TEST_UUID} vdi-uuid=${PASSTHROUGH_VDI}`
ssh ${MASTER_HOST} xe vm-start vm=${VM_HOST_UNDER_TEST_UUID}
until ping -c1 ${XCP_HOST_UNDER_TEST_IP} &>/dev/null; do :; done
sleep 20

# try EXT3
ssh ${XCP_HOST_UNDER_TEST} 'mkfs.ext3 /dev/sdb2 && echo /dev/sdb2 /mnt/ext3 ext3 >>/etc/fstab && mkdir -p /mnt/ext3 && mount /dev/sdb2 && df'
SR_EXT3_UUID=`ssh ${XCP_HOST_UNDER_TEST} "xe sr-create host-uuid=${XCP_HOST_UNDER_TEST_UUID} name-label=test-ext3-sr type=file other-config:o_direct=false device-config:location=/mnt/ext3/test-ext3-sr"`
TEST_EXT3_VDI=`ssh ${XCP_HOST_UNDER_TEST} xe vdi-create sr-uuid=${SR_EXT3_UUID} name-label=test-ext3-vdi virtual-size=214748364800`
TEST_VBD=`ssh ${XCP_HOST_UNDER_TEST} xe vbd-create device=1 type=Disk mode=RW vm-uuid=${INCEPTION_VM_UUID} vdi-uuid=${TEST_EXT3_VDI}`


ssh ${XCP_HOST_UNDER_TEST} reboot || true
sleep 20
until ping -c1 ${XCP_HOST_UNDER_TEST_IP} &>/dev/null; do :; done
sleep 20

ssh ${XCP_HOST_UNDER_TEST} xe vm-start vm=${INCEPTION_VM_UUID} on=${XCP_HOST_UNDER_TEST_UUID}
sleep 2
until ping -c1 ${INCEPTION_VM_IP} &>/dev/null; do :; done
sleep 20
ssh ${INCEPTION_VM} echo FROM BENCH
ssh ${INCEPTION_VM} 'apk add gcc zlib-dev libaio libaio-dev make linux-headers git binutils musl-dev; git clone https://github.com/axboe/fio fio; cd fio; ./configure && make&& make install'
ssh ${INCEPTION_VM} 'mkfs.ext3 /dev/xvdb && mount /dev/xvdb /mnt;df'
ssh ${INCEPTION_VM} 'cd /mnt;sync;/usr/local/bin/fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=write --bs=4k --direct=1 --size=512M --numjobs=2 --runtime=30 --group_reporting' > ext3_write_result
ssh ${INCEPTION_VM} 'cd /mnt;sync;/usr/local/bin/fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=write --bs=4k --direct=1 --size=512M --numjobs=2 --runtime=30 --group_reporting' >> ext3_write_result
ssh ${INCEPTION_VM} 'cd /mnt;sync;/usr/local/bin/fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=read --bs=4k --direct=1 --size=512M --numjobs=2 --runtime=30 --group_reporting' > ext3_read_result
ssh ${INCEPTION_VM} 'cd /mnt;sync;/usr/local/bin/fio --name=randwrite --ioengine=libaio --iodepth=1 --rw=read --bs=4k --direct=1 --size=512M --numjobs=2 --runtime=30 --group_reporting' >> ext3_read_result
ssh ${XCP_HOST_UNDER_TEST} xe vm-shutdown uuid=${INCEPTION_VM_UUID}

# try ZFS
# install binaries that don't use O_DIRECT
rsync -r zfs ${XCP_HOST_UNDER_TEST}:
scp /Users/nraynaud/dev/xenserver-build-env/blktap-3.5.0-1.12test.x86_64.rpm ${XCP_HOST_UNDER_TEST}:
ssh ${XCP_HOST_UNDER_TEST} yum remove -y blktap
ssh ${XCP_HOST_UNDER_TEST} yum install -y blktap-3.5.0-1.12test.x86_64.rpm
ssh ${XCP_HOST_UNDER_TEST} yum install -y zfs/*.rpm
ssh ${XCP_HOST_UNDER_TEST} depmod -a
ssh ${XCP_HOST_UNDER_TEST} modprobe zfs
ssh ${XCP_HOST_UNDER_TEST} zpool create -f -m /mnt/zfs tank /dev/sdb1
ssh ${XCP_HOST_UNDER_TEST} zfs set sync=disabled tank
ssh ${XCP_HOST_UNDER_TEST} zfs set compression=lz4 tank
ssh ${XCP_HOST_UNDER_TEST} zfs list


SR_ZFS_UUID=`ssh ${XCP_HOST_UNDER_TEST} "xe sr-create host-uuid=${XCP_HOST_UNDER_TEST_UUID} name-label=test-zfs-sr type=file other-config:o_direct=false device-config:location=/mnt/zfs/test-zfs-sr"`
TEST_ZFS_VDI=`ssh ${XCP_HOST_UNDER_TEST} xe vdi-create sr-uuid=${SR_ZFS_UUID} name-label=test-zfs-vdi virtual-size=214748364800`
# this line avoids O_DIRECT in reads
ssh ${XCP_HOST_UNDER_TEST} "sed -i.bak 's/# unbuffered = true/unbuffered = false/' /etc/sparse_dd.conf"
# try various clone situations
ssh ${XCP_HOST_UNDER_TEST} xe vdi-copy uuid=${TEST_ZFS_VDI} sr-uuid=${SR_ZFS_UUID}
ssh ${XCP_HOST_UNDER_TEST} xe vdi-copy uuid=${TEST_ZFS_VDI} sr-uuid=${SR_EXT3_UUID}
ssh ${XCP_HOST_UNDER_TEST} xe vdi-copy uuid=${TEST_EXT3_VDI} sr-uuid=${SR_ZFS_UUID}

this script complete to the end without error.

nraynaud

If other people can reproduce my results, I propose to directly change the parameter in the XCP-ng distribution RPM.

olivierlambert

Your package is experimental, so feel free to add the modification inside it

borzel

@nraynaud said in Testing ZFS with XCP-ng:

If other people can reproduce my results

with the change in /etc/sparse_dd.conf I can copy my VMs from:

EXT3 -> ZFS
ZFS -> ZFS
ZFS -> EXT3

Yeha!

Thanks for your work!

By the way, my XCP-ng replication host at work is working just fine with ZFS-SR. All stable like ZFS should be.