*** Bug 824647 has been marked as a duplicate of this bug. ***

We will get this for free when RHEV switches to QEMU 2.1.0.

(In reply to Ademar Reis from comment #0)
> Stefan is working on the proper data-plane implementation that covers all of
> the block layer and this BZ is for the backport of such work. The current
> implementation duplicates blocklayer code and is very limited, serving only
> as a tech-preview experiment.

Verify this issue with the following supported parts.
host info:
# uname -r && rpm -q qemu-kvm-rhev && rpm -q seabios
3.10.0-145.el7.x86_64
qemu-kvm-rhev-2.1.0-2.el7.x86_64
seabios-1.7.5-4.el7.x86_64
guest info:
# uname -r
3.10.0-145.el7.x86_64

> Below are some data-plane features which are missing in the current version
> of qemu-kvm.
> 
>  * Image formats (qcow2)
>    Dataplane currently only supports raw image files.  It should be
>    possible to use image formats like qcow2.
> 
1.create a qcow2 data disk image.
# qemu-img create -f qcow2 /home/my-data-disk.qcow2 10G
Formatting '/home/my-data-disk.qcow2', fmt=qcow2 size=10737418240 encryption=off cluster_size=65536 lazy_refcounts=off
2.launch the qcow2 data disk image to KVM guest.
e.g:...-drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7
3.verify the disk can be detected in guest and can work well with format/dd.
# fdisk -l                                      <------------detect it in guest
# mkfs.ext4 /dev/vda                            <------------successfully
# dd if=/dev/zero of=/dev/vda bs=1M count=1000  <------------successfully

>  * Protocols (iSCSI, GlusterFS, Ceph, NBD)
>    Dataplane currently only supports local files using Linux AIO.
>    Network protocols like NBD, iSCSI, GlusterFS, and Ceph should be
>    supported.
> 
- iSCSI:
e.g.:...-drive file=/dev/disk/by-path/ip-10.66.33.253:3260-iscsi-iqn.2014.sluo.com:iscsi.storage.1-lun-1,if=none,id=drive-data-disk,format=raw,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7

Verify the disk can be detected in guest and can work well with format/dd.
# fdisk -l                                     <------------detect it in guest
# mkfs.ext4 /dev/vda                           <------------successfully
# dd if=/dev/zero of=/dev/vda bs=1M count=1000 <------------successfully

- Libiscsi:
e.g:...-drive file=iscsi://10.66.33.253:3260/iqn.2014.sluo.com:iscsi.storage.1/1,if=none,id=drive-data-disk,format=raw,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7

Verify the disk can be detected in guest and can work well with format/dd.
# fdisk -l                                     <------------detect it in guest
# mkfs.ext4 /dev/vda                           <------------successfully
# dd if=/dev/zero of=/dev/vda bs=1M count=1000 <------------successfully

- GluserFS:
# qemu-img create -f qcow2 gluster://10.66.106.22/sluo_volume/my-data-disk.qcow2 10G
Formatting 'gluster://10.66.106.22/sluo_volume/my-data-disk.qcow2', fmt=qcow2 size=10737418240 encryption=off cluster_size=65536 

# qemu-img info gluster://10.66.106.22/sluo_volume/my-data-disk.qcow2
image: gluster://10.66.106.22/sluo_volume/my-data-disk.qcow2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 140K
cluster_size: 65536
Format specific information:
    compat: 0.10

e.g:...-drive file=gluster://10.66.106.22/sluo_volume/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7

Verify the disk can be detected in guest and can work well with format/dd.
# fdisk -l                                     <------------detect it in guest
# mkfs.ext4 /dev/vda                           <------------successfully
# dd if=/dev/zero of=/dev/vda bs=1M count=1000 <------------successfully

- NBD:
# nbd-server 12345 /home/my-data-disk.qcow2

** (process:28046): WARNING **: Specifying an export on the command line is deprecated.

** (process:28046): WARNING **: Please use a configuration file instead.

e.g:...-drive file=nbd:10.66.11.154:12345,if,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7

Verify the disk can be detected in guest and can work well with format/dd.
# fdisk -l                                     <------------detect it in guest
# mkfs.ext4 /dev/vda                           <------------successfully
# dd if=/dev/zero of=/dev/vda bs=1M count=1000 <------------successfully

- Ceph:

I did not use the Ceph in the past, just leave Ceph along first, i will investigate it later and try it. 

>  * I/O throttling
>    I/O throttling requires the new AioContext timer support which is
>    currently being merged upstream.
> 

>  * Hot unplug
>    Due to the way bdrv_in_use() is currently used to prevent hot unplug,
>    the virtio-blk-pci adapter cannot be hot unplugged.  The hot unplug
>    command will fail with EBUSY.
> 
e.g:...-drive file=/dev/disk/by-path/ip-10.66.33.253:3260-iscsi-iqn.2014.sluo.com:iscsi.storage.1-lun-1,if=none,id=drive-data-disk,format=raw,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,config-wce=off,x-data-plane=on,bus=pci.0,addr=0x7
(qemu) device_del data-disk
(qemu) info block    <-------hotunplug successfully.
guest ]# fdisk -l    <-------disappear from guest.
guest ]# dmesg       <-------not see any error

>  * iothreads as objects
>    The user should be able to define the number of iothreads and bind
>    devices to specific threads.  iothreads should be discoverable using
>    a QMP query-iothreads command, which includes thread IDs suitable for
>    CPU affinity setting.
> 
e.g:...-object iothread,id=iothread0 -drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,iothread=iothread0,bus=pci.0,addr=0x7

discoverable iothreads via QMP:
{"execute":"query-iothreads"}
{"return": [{"thread-id": 6072, "id": "iothread0"}]}

>  * Runtime NBD exports
>    The runtime NBD server should not interfere with dataplane.  This
>    will allow image fleecing and other NBD export users to coexist with
>    dataplane.
> 
1).launch a KVM guest with data-plane.
e.g:...-object iothread,id=iothread0 -drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk0,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk0,id=data-disk0,iothread=iothread0,bus=pci.0,addr=0x7
2).nbd_server_start nbd_server_start [-a] [-w] host:port -- serve block devices on the given host and port and export a block device via NBD.
{"execute":"qmp_capabilities"}
{"return": {}}
{ "execute": "nbd-server-start", "arguments": { "addr": { "type": "inet", "data": { "host": "10.66.11.154", "port": "1234" } } } }
{"return": {}}
{ "execute": "nbd-server-add", "arguments": { "device": "drive-data-disk0", "writable": true } }
{"return": {}}
3).read/write to the nbd target.
# qemu-img info nbd://10.66.11.154:1234/drive-data-disk0
image: 
file format: raw
virtual size: 10G (10737418240 bytes)
disk size: unavailable
# qemu-io -c 'read 512 1024' nbd://10.66.11.154:1234/drive-data-disk0
read 1024/1024 bytes at offset 512
1 KiB, 1 ops; 0.0003 sec (2.713 MiB/sec and 2777.7778 ops/sec)
# qemu-io -c 'write 512 1024' nbd://10.66.11.154:1234/drive-data-disk0
wrote 1024/1024 bytes at offset 512
1 KiB, 1 ops; 0.0005 sec (1.922 MiB/sec and 1968.5039 ops/sec)

>  * Block jobs
>    Block jobs should not interfere with dataplane.  Currently block jobs
>    cannot be started (EBUSY).
> 
e.g.:...-object iothread,id=iothread0 -drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop -device virtio-blk-pci,drive=drive-data-disk,id=data-disk,iothread=iothread0,bus=pci.0,addr=0x7

- do block stream:
{ "execute": "drive-mirror", "arguments": { "device": "drive-data-disk", "target": "/root/sn1", "format": "qcow2", "mode": "absolute-paths", "sync": "full", "speed": 1000000000, "on-source-error": "stop", "on-target-error": "stop" } }
{"error": {"class": "GenericError", "desc": "Device 'drive-data-disk' is busy: block device is in use by data plane"}}

- do block mirror:
{ "execute": "blockdev-snapshot-sync", "arguments": { "device": "drive-data-disk","snapshot-file": "/home/snap", "format": "qcow2" } }
{"error": {"class": "GenericError", "desc": "Device 'drive-data-disk' is busy: block device is in use by data plane"}}

> This BZ will be closed once the first patch-series implementing the bulk of
> the work is backported and the new implementation is ready for wider
> testing. If necessary, extra BZs will be open to track missing
> functionalities by then.

Best Regards,
sluo

(In reply to Sibiao Luo from comment #4)
> (In reply to Ademar Reis from comment #0)
> > Stefan is working on the proper data-plane implementation that covers all of
> > the block layer and this BZ is for the backport of such work. The current
> > implementation duplicates blocklayer code and is very limited, serving only
> > as a tech-preview experiment.
> 
> Verify this issue with the following supported parts.
> host info:
> # uname -r && rpm -q qemu-kvm-rhev && rpm -q seabios
> 3.10.0-145.el7.x86_64
> qemu-kvm-rhev-2.1.0-2.el7.x86_64
> seabios-1.7.5-4.el7.x86_64
> guest info:
> # uname -r
> 3.10.0-145.el7.x86_64
> 
> 
> >  * I/O throttling
> >    I/O throttling requires the new AioContext timer support which is
> >    currently being merged upstream.
> > 
> 
1.launch a KVM guest with data-plane.
e.g:...-object iothread,id=iothread0 -drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk0,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop,bps=1024000,bps_rd=0,bps_wr=0,iops=1024000,iops_rd=0,iops_wr=0 -device virtio-blk-pci,drive=drive-data-disk0,id=data-disk0,iothread=iothread0,bus=pci.0,addr=0x7
(qemu) info block
drive-system-disk: /home/RHEL-7.0-20140507.0-Server-x86_64.qcow2 (qcow2)

drive-data-disk0: /home/my-data-disk.qcow2 (qcow2)
    I/O throttling:   bps=1024000 bps_rd=0 bps_wr=0 bps_max=102400 bps_rd_max=0 bps_wr_max=0 iops=1024000 iops_rd=0 iops_wr=0 iops_max=102400 iops_rd_max=0 iops_wr_max=0 iops_size=0
...
2).query the block info via HMP/QMP monitor.
{"execute":"query-block"}
{"return": [...{"io-status": "ok", "device": "drive-data-disk0", "locked": false, "removable": false, "inserted": {"iops_rd": 0, "detect_zeroes": "off", "image": {"virtual-size": 10737418240, "filename": "/home/my-data-disk.qcow2", "cluster-size": 65536, "format": "qcow2", "actual-size": 140320768, "format-specific": {"type": "qcow2", "data": {"compat": "1.1", "lazy-refcounts": false}}, "dirty-flag": false}, "iops_wr": 0, "ro": false, "backing_file_depth": 0, "drv": "qcow2", "bps_max": 102400, "iops": 1024000, "bps_wr": 0, "encrypted": false, "bps": 1024000, "bps_rd": 0, "iops_max": 102400, "file": "/home/my-data-disk.qcow2", "encryption_key_missing": false}, "type": "unknown"}, {"io-status": "ok", "device": "ide1-cd0", "locked": false, "removable": true, "tray_open": false, "type": "unknown"}, {"device": "floppy0", "locked": false, "removable": true, "tray_open": false, "type": "unknown"}, {"device": "sd0", "locked": false, "removable": true, "tray_open": false, "type": "unknown"}]}
3).do fio to the disk in guest.
# fio --filename=/dev/vda --direct=1 --rw=randrw --bs=100K --size=10M --name=test --iodepth=100 --ioengine=libaio
test: (g=0): rw=randrw, bs=100K-100K/100K-100K/100K-100K, ioengine=libaio, iodepth=100
fio-2.1.10
Starting 1 process
Jobs: 1 (f=1): [m] [3.2% done] [0KB/0KB/0KB /s] [0/0/0 iops] [eta 05m:31s]
test: (groupid=0, jobs=1): err= 0: pid=4230: Mon Sep  1 02:17:19 2014
  read : io=4900.0KB, bw=501659B/s, iops=4, runt= 10002msec
    slat (usec): min=6, max=34, avg=10.53, stdev= 4.11
    clat (msec): min=1, max=10001, avg=9390.61, stdev=2413.35
     lat (msec): min=1, max=10001, avg=9390.62, stdev=2413.35
    clat percentiles (usec):
     |  1.00th=[ 1352],  5.00th=[99840], 10.00th=[10027008], 20.00th=[10027008],
     | 30.00th=[10027008], 40.00th=[10027008], 50.00th=[10027008], 60.00th=[10027008],
     | 70.00th=[10027008], 80.00th=[10027008], 90.00th=[10027008], 95.00th=[10027008],
     | 99.00th=[10027008], 99.50th=[10027008], 99.90th=[10027008], 99.95th=[10027008],
     | 99.99th=[10027008]
    bw (KB  /s): min=   39, max=   39, per=7.98%, avg=39.00, stdev= 0.00
  write: io=5300.0KB, bw=542611B/s, iops=5, runt= 10002msec
    slat (usec): min=8, max=22, avg=15.28, stdev= 3.32
    clat (usec): min=10000K, max=10001K, avg=10000757.38, stdev=421.06
     lat (usec): min=10000K, max=10001K, avg=10000772.89, stdev=418.90
    clat percentiles (msec):
     |  1.00th=[10028],  5.00th=[10028], 10.00th=[10028], 20.00th=[10028],
     | 30.00th=[10028], 40.00th=[10028], 50.00th=[10028], 60.00th=[10028],
     | 70.00th=[10028], 80.00th=[10028], 90.00th=[10028], 95.00th=[10028],
     | 99.00th=[10028], 99.50th=[10028], 99.90th=[10028], 99.95th=[10028],
     | 99.99th=[10028]
    lat (msec) : 2=0.98%, 20=0.98%, 250=0.98%, >=2000=97.06%
  cpu          : usr=0.00%, sys=0.02%, ctx=93, majf=0, minf=29
  IO depths    : 1=1.0%, 2=2.0%, 4=3.9%, 8=7.8%, 16=15.7%, 32=31.4%, >=64=38.2%
     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=75.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=25.0%
     issued    : total=r=49/w=53/d=0, short=r=0/w=0/d=0
     latency   : target=0, window=0, percentile=100.00%, depth=100

Run status group 0 (all jobs):
   READ: io=4900KB, aggrb=489KB/s, minb=489KB/s, maxb=489KB/s, mint=10002msec, maxt=10002msec
  WRITE: io=5300KB, aggrb=529KB/s, minb=529KB/s, maxb=529KB/s, mint=10002msec, maxt=10002msec

Disk stats (read/write):
  vda: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%

Best Regards,
sluo

*** Bug 1101572 has been marked as a duplicate of this bug. ***

Current dataplane status.

Supported:
 * Image formats
 * I/O throttling
 * Block jobs
 * GlusterFS, RBD, iSCSI, NBD

Unsupported:
 * External and internal snapshots
 * QMP 'transaction' command
 * Eject
 * qcow2 encryption

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2015-0624.html