Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

resolve and document most common erasure coded pool pain points #3194

Merged
merged 5 commits into from Jan 18, 2015
Merged

resolve and document most common erasure coded pool pain points #3194

merged 5 commits into from Jan 18, 2015

Commits on Jan 15, 2015

  1. crush: update tries statistics for indep rules 

    http://tracker.ceph.com/issues/10349 Fixes: #10349

Signed-off-by: Loic Dachary <ldachary@redhat.com>
    @ldachary
    ldachary committed Jan 15, 2015
    Configuration menu
    Copy the full SHA
    4d07a32 View commit details
    Browse the repository at this point in the history

  2. crush: set_choose_tries = 100 for erasure code rulesets 

    It is common for people to try to map 9 OSDs out of a 9 OSDs total ceph
cluster. The default tries (50) will frequently lead to bad mappings for
this use case. Changing it to 100 makes no significant CPU performance
difference, as tested manually by running crushtool on one million
mappings.

http://tracker.ceph.com/issues/10353 Fixes: #10353

Signed-off-by: Loic Dachary <ldachary@redhat.com>
    @ldachary
    ldachary committed Jan 15, 2015
    Configuration menu
    Copy the full SHA
    2f87ac8 View commit details
    Browse the repository at this point in the history

  3. erasure-code: set max_size to chunk_count() instead of 20 

    The ruleset created for an erasure coded pool has max_size set to a
fixed value of 20, which may be incorrect when more than 20 chunks are
needed and lead to obscure errors. Set it to the number of chunks,
i.e. k+m most of the time.

In a cluster with few OSDs (9 for instance), setting max_size to 20
causes performance problems when injecting a new crushmap. The monitor
will call CrushTester::test which tries 1024 mappins for all sizes
ranging from min_size to max_size. Each attempt to map more OSDs than
available will exhaust all retries (50 by default) and it takes a
significant amount of time. In a cluster with 9 OSDs, testing one such
ruleset can take up to 5 seconds.

Since the test blocks the monitor leader, a few erasure coded rulesets
will block the monitor long enough to exceed the timeouts and trigger an
election.

http://tracker.ceph.com/issues/10363 Fixes: #10363

Signed-off-by: Loic Dachary <ldachary@redhat.com>
    @ldachary
    ldachary committed Jan 15, 2015
    Configuration menu
    Copy the full SHA
    8b64fe9 View commit details
    Browse the repository at this point in the history

  4. documentation: add troubleshooting erasure coded PGs section 

    Add a new section to the PG troubleshooting section that covers the most
common problems reported when an erasure coded pool fails to properly
map PGs to enough OSDs.

http://tracker.ceph.com/issues/10350 Fixes: #10350

Signed-off-by: Loic Dachary <ldachary@redhat.com>
    @ldachary
    ldachary committed Jan 15, 2015
    Configuration menu
    Copy the full SHA
    02cab93 View commit details
    Browse the repository at this point in the history

  5. erasure-code: tests use different pool/profile names 

    Use different erasure coded pool names and profiles to avoid deletion /
creation races. The more expensive alternative is to run a different
cluster for each test.

Signed-off-by: Loic Dachary <ldachary@redhat.com>
    @ldachary
    ldachary committed Jan 15, 2015
    Configuration menu
    Copy the full SHA
    dac666f View commit details
    Browse the repository at this point in the history