Desktop based Ceph cluster for file sharing

July 1st 2013, Heinlein setup a Ceph cuttlefish ( now upgraded to version 0.61.8 ) cluster using the desktop of seven employees willing to host a ceph node and share part of their disk. The nodes are partly connected with 1Gb/s links and some only have 100Mb/s. The cluster supports a 4TB ceph file system

ceph-office$ df -h .
Filesystem                 Size  Used Avail Use% Mounted on
x.x.x.x,y.y.y.y,z.z.z.z:/  4,0T  2,0T  2,1T  49% /mnt/ceph-office

which is used as a temporary space to exchange files. On a typical day at least one desktop is switched off and on again. The cluster has been self healing since its installation, with the only exception of a placement group being stuck and fixed with a manual pg repair .
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Resizeable and resilient mail storage with Ceph

A common use case for Ceph is to store mail as objects using the S3 API. Although most mail servers do not yet support such a storage backend, deploying them on Ceph block devices is a beneficial first step. The disk can be resized live, while the mail server is running, and will remain available even when a machine goes down. In the following example it gains ~100GB every 30 seconds:

$ df -h /data/bluemind
Filesystem      Size  Used Avail Use% Mounted on
/dev/rbd2       1.9T  196M  1.9T   1% /data/bluemind
$ sleep 30 ; df -h /data/bluemind
Filesystem      Size  Used Avail Use% Mounted on
/dev/rbd2       2.0T  199M  2.0T   1% /data/bluemind

When the mail system is upgraded to a S3 capable mail storage backend, it will be able to use the Ceph S3 API right away: Ceph uses the same underlying servers for both purposes ( block and object storage ).
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HOWTO run a Ceph Q&A suite

Ceph has extensive Q&A suites that are made of individual teuthology tasks ( see btrfs.yaml for instance ). The helper script could be used as follows to run the entire rados suite:

./ rados wip-5510 testing \ basic master plana

Where wip-5510 is the branch to be tested as compiled by gitbuilder ( which happens automatically after each commit ), testing is the kernel to run on the test machines which is relevant when using krbd, basic is the compilation flavor of the wip-5510 branch ( could be notcmalloc or gcov ) and master is the teuthology branch to use. plana specifies the type of machines to be used, which is only relevant if using the inktank lab.
The queue_host defined in .teuthology.yaml

queue_port: 11300

will schedule a number of jobs ( ~300 for rados ) and send a mail when they complete.

name loic-2013-08-14_22:00:20-rados-wip-5510-testing-basic-plana
INFO:teuthology.suite:Collection basic in /home/loic/src/ceph-qa-suite/suites/rados/basic
INFO:teuthology.suite:Running teuthology-schedule with facets collection:basic clusters:fixed-2.yaml fs:btrfs.yaml msgr-failures:few.yaml tasks:rados_api_tests.yaml
Job scheduled with ID 106579
INFO:teuthology.suite:Running teuthology-schedule with facets collection:basic clusters:fixed-2.yaml fs:btrfs.yaml msgr-failures:few.yaml tasks:rados_cls_all.yaml
Job scheduled with ID 106580
INFO:teuthology.suite:Running teuthology-schedule with facets collection:verify 1thrash:none.yaml clusters:fixed-2.yaml fs:btrfs.yaml msgr-failures:few.yaml tasks:rados_cls_all.yaml validater:valgrind.yaml
Job scheduled with ID 106880
Job scheduled with ID 106881

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HOWTO valgrind Ceph with teuthology

Teuthology can run a designated daemon with valgrind and preserve the report for analysis. The notcmalloc flavor is preferred to silence valgrind errors unrelated to Ceph itself.

- install:
   project: ceph
   branch: wip-5510
   flavor: notcmalloc

A daemon running with valgrind is much slower and warnings will show in the logs that should be marked as non relevant in this context:

    - slow request
    - clocks
    - wrongly marked me down
    - objects unfound and apparently lost

The first osd is marked to be run with valgrind:

- ceph:
      osd.0: --tool=memcheck

After running teuthology with

./virtualenv/bin/teuthology -v --archive /tmp/wip-5510-valgrind \
  --owner \
  ~/private/ceph/targets.yaml \

errors may show

DEBUG:teuthology.run_tasks:Exception was not quenched, exiting: Exception: saw valgrind issues data:
{duration: 344.2433888912201, failure_reason: saw valgrind issues, flavor: notcmalloc,
  owner:, success: false}

And the valgrind XML report containing the details about the error can be retrieved from the /tmp/wip-5510-valgrind/remote/ubuntu@target1/log/valgrind/osd.0.log.gz
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HOWTO install Ceph teuthology on OpenStack

Teuthology is used to run Ceph integration tests. It is installed from sources and will use newly created OpenStack instances as targets:

$ cat targets.yaml
  ubuntu@target1.novalocal: ssh-rsa AAAAB3NzaC1yc2...
  ubuntu@target2.novalocal: ssh-rsa AAAAB3NzaC1yc2...

They allow password free ubuntu ssh connection with full sudo privileges from the machine running teuthology. A Ubuntu precise 12.04.2 target must be configured with:

$ wget -q -O- ';a=blob_plain;f=keys/release.asc' | \
  sudo apt-key add -
$ echo '    ubuntu hard nofile 16384' > /etc/security/limits.d/ubuntu.conf

It can then be tried with a configuration file that does nothing but install Ceph and run the daemons.

$ cat noop.yaml
check-locks: false
- - mon.a
  - osd.0
- - osd.1
  - client.0
- install:
   project: ceph
   branch: stable
- ceph:

The output should look like this:

$ ./virtualenv/bin/teuthology targets.yaml noop.yaml
INFO:teuthology.run_tasks:Running task internal.save_config...
INFO:teuthology.task.internal:Saving configuration
INFO:teuthology.run_tasks:Running task internal.check_lock...
INFO:teuthology.task.internal:Lock checking disabled.
INFO:teuthology.run_tasks:Running task internal.connect...
INFO:teuthology.task.internal:Opening connections...
DEBUG:teuthology.task.internal:connecting to ubuntu@teuthology2.novalocal
DEBUG:teuthology.task.internal:connecting to ubuntu@teuthology1.novalocal
... data:
{duration: 363.5891010761261, flavor: basic, owner: ubuntu@teuthology, success: true}

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