Testing ZFS with XCP-ng

borzel

@stormi said in Testing ZFS with XCP-ng:

@borzel It would be nice also to improve https://github.com/xcp-ng/xcp/wiki/ZFS-on-XCP-ng-7.5-and-later because I wrote it and I never used zfs!

I have no write permissions

borzel

Good ressource with a lot of information, how to really use ZFS, build storages, tuning, etc.: https://www.zfsbuild.com

buzzzo

Zfs is a local sr and imho does not add too much advantages vs classic ext sr

The real value of zfs is to use built in replication to remote zfs system.
Proxmox has built a very interesting solutions around it: async replication of vm on a another node.

I know xoa already offer a similar solution but is snapshot based and everyone knows the performance and size problem with this approach.

borzel

@buzzzo said in Testing ZFS with XCP-ng:

Zfs is a local sr and imho does not add too much advantages vs classic ext sr

meeeep

ZFS uses (in standard configuration) half the RAM as read cache
with sync=disabled your writes are faster (but synced to discs every 5 seconds; in one sequential batch - efficient use of slow spinning drives!)
it has checksums from fs-layer down to the device
it's awesome

know xoa already offer a similar solution but is snapshot based and everyone knows the performance and size problem with this approach.

If we all had 48 hours a day and more people in the team, we could fully integrate ZFS into XCP-ng (with all bells and whistles). But for now we are happy to have the first step done - loose integrate ZFS to start using it and testing stability of the dom0 with ZFS in it.

olivierlambert

@buzzzo Double meeeep

On file level SR (ext, NFS, local ZFS, XOSAN), there is no space issue doing snapshots. Also, perfs are good even with snapshots if you don't have an asthmatic SR.

buzzzo

@olivierlambert meeep!!!

olivierlambert

Meep meep!

borzel

I tested latest and greatest XO (5.24.1 from sources) with latest XCP-ng 7.5 (incl. xcp-ng-extra repo/ZFS). Backups do not work

If the VDI is on a ext-SR, all is fine, backup working.
If the VDI is on a File-SR (ZFS based), the backup says "VDI_ERROR" or "VDI Chain to long". I will provide logfiles tomorrow if needed.

Setup of my File-SR:
xe sr-create host-uuid=<xxx> name-label=zfssr type=file other-config:o_direct=false device-config:location=/zfspool/zfssr

olivierlambert

VDI chain too long doesn't seems related. It means you have a VDI chain that's around 30 files.

Can you provide the exact/detailed error log?

borzel

borzel

I searched in xensource.log, SMlog and syslog, no related entries found

How can I increase the loglevel of XO?

Here's the log output if I start this job again:

Aug 15 01:10:35 ubuntu xo-server[616]: 2018-08-14T23:10:35.241Z xo:xapi Snapshotting VM pmg as [XO Backup test] pmg
Aug 15 01:10:36 ubuntu xo-server[616]: 2018-08-14T23:10:36.948Z xo:xapi exporting VDI pmg 0
Aug 15 01:10:41 ubuntu xo-server[616]: 2018-08-14T23:10:41.289Z xo:xapi Deleting VM [XO Backup test] pmg
Aug 15 01:10:41 ubuntu xo-server[616]: 2018-08-14T23:10:41.585Z xo:xapi Deleting VDI pmg 0

It's nearly nothing...

nraynaud

@borzel > The error is often in the Settings->Logs panel in XO in this case

borzel

@nraynaud no, it's as empty as it could be

borzel

I found something in /var/log/xensource.log (used tail -f /var/log/xensource.log | grep -i 'error')

Aug 14 23:19:10 hw xapi: [error|hw|63005 INET :::80|[XO] VDI Export R:3001f7e5aa17|vhd_tool_wrapper] vhd-tool failed, returning VDI_IO_ERROR
Aug 14 23:19:10 hw xapi: [error|hw|63005 INET :::80|[XO] VDI Export R:3001f7e5aa17|vhd_tool_wrapper] vhd-tool output: vhd-tool: internal error, uncaught exception:#012          Unix.Unix_error(Unix.EINVAL, "open", "/var/run/sr-mount/9fc67ea3-c9b3-5e62-ecc3-7d1debf81744/6781ab7b-c475-4d72-a7d0-b2aeca2e81e3.vhd")#012          Raised at file "src/core/lwt.ml", line 3008, characters 20-29#012          Called from file "src/unix/lwt_main.ml", line 42, characters 8-18#012          Called from file "src/impl.ml", line 811, characters 4-23#012          Called from file "src/cmdliner_term.ml", line 27, characters 19-24#012          Called from file "src/cmdliner.ml", line 27, characters 27-34#012          Called from file "src/cmdliner.ml", line 106, characters 32-39
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] [XO] VDI Export R:3001f7e5aa17 failed with exception Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] Raised Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 1/13 xapi @ hw Raised at file ocaml/xapi/vhd_tool_wrapper.ml, line 59
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 2/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 3/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 4/13 xapi @ hw Called from file ocaml/xapi/export_raw_vdi.ml, line 47
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 5/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 6/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 7/13 xapi @ hw Called from file ocaml/xapi/export_raw_vdi.ml, line 54
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 8/13 xapi @ hw Called from file ocaml/xapi/export_raw_vdi.ml, line 65
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 9/13 xapi @ hw Called from file ocaml/xapi/server_helpers.ml, line 73
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 10/13 xapi @ hw Called from file ocaml/xapi/server_helpers.ml, line 91
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 11/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 12/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace] 13/13 xapi @ hw Called from file lib/backtrace.ml, line 177
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:315adbf2ec6c|backtrace]
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] VDI.export_raw_vdi D:315adbf2ec6c failed with exception Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] Raised Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 1/13 xapi @ hw Raised at file lib/debug.ml, line 187
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 2/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 3/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 4/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 5/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 6/13 xapi @ hw Called from file ocaml/xapi/xapi_http.ml, line 185
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 7/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 8/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 9/13 xapi @ hw Called from file ocaml/xapi/server_helpers.ml, line 73
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 10/13 xapi @ hw Called from file ocaml/xapi/server_helpers.ml, line 91
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 11/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 22
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 12/13 xapi @ hw Called from file lib/xapi-stdext-pervasives/pervasiveext.ml, line 26
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace] 13/13 xapi @ hw Called from file lib/backtrace.ml, line 177
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80|VDI.export_raw_vdi D:fc8d0f58f1be|backtrace]
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80||backtrace] VDI.export_raw_vdi D:fc8d0f58f1be failed with exception Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80||backtrace] Raised Server_error(VDI_IO_ERROR, [ Device I/O errors ])
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80||backtrace] 1/1 xapi @ hw Raised at file (Thread 63005 has no backtrace table. Was with_backtraces called?, line 0
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80||backtrace]
Aug 14 23:19:11 hw xapi: [error|hw|63005 INET :::80||xapi] Unhandled Api_errors.Server_error(VDI_IO_ERROR, [ Device I/O errors ])

olivierlambert

I'll try to run some tests on my side.

stormi

@borzel I'm not very familiar with github wikis, but I think you can do pull requests against the wiki.

borzel

@stormi wiki issue is allready solved

nraynaud

@borzel good catch, it's another O_DIRECT issue.

nraynaud

@borzel I am struggling to match the error lines in your log with a source code, can you tell me what version of vhd-tool you have installed please ? (yum info vhd-tool)

borzel

@nraynaud

# yum info vhd-tool
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Installed Packages
Name        : vhd-tool
Arch        : x86_64
Version     : 0.20.0
Release     : 4.2.xcp.el7.centos.extras
Size        : 40 M
Repo        : installed
From repo   : xcp-ng-extras
Summary     : Command-line tools for manipulating and
            : streaming .vhd format files
URL         : https://github.com/xapi-project/vhd-tool
License     : LGPL+linking exception
Description : Simple command-line tools for manipulating an
            : streaming .vhd format file.