ceph blocked requests in the cluster caused by deep-scrubing operations
· 3 min read
With the default options you will see blocked requests in the cluster caused by deep-scrubing operations
recomended deep scrub options to minimize the impact of scrub/deep-scrub in the ceph cluster
the following options define the scrub and deep-scrub behaviour, by cpu load, osd scheduler priority, defined check intervals and ceph cluster health state
[osd]
#reduce scrub impact
osd max scrubs = 1
osd scrub during recovery = false
osd scrub max interval = 4838400 # 56 days
osd scrub min interval = 2419200 # 28 days
osd deep scrub interval = 2419200
osd scrub interval randomize ratio = 1.0
# osd deep scrub randomize ratio = 1.0
osd scrub priority = 1
osd scrub chunk max = 1
osd scrub chunk min = 1
osd deep scrub stride = 1048576 # 1 MB
osd scrub load threshold = 5.0
osd scrub sleep = 0.3
osd max scrubs
osd max scrubs
Description: The maximum number of simultaneous scrub operations for a Ceph OSD Daemon.
Type: 32-bit Int
Default: 1
osd scrub during recovery
Description: Allow scrub during recovery. Setting this to false will disable scheduling new scrub (and deep–scrub) while there is active recovery. Already running scrubs will be continued. This might be useful to reduce load on busy clusters.
Type: Boolean
Default: true
osd scrub min interval
Description: The minimal interval in seconds for scrubbing the Ceph OSD Daemon when the Ceph Storage Cluster load is low.
Type: Float
Default: Once per day. 60*60*24
5,14 6%
osd scrub interval randomize ratio
Description: Add a random delay to osd scrub min interval when scheduling the next scrub job for a placement group. The delay is a random value less than osd scrub min interval * osd scrub interval randomized ratio. So the default setting practically randomly spreads the scrubs out in the allowed time window of [1, 1.5] * osd scrub min interval.
Type: Float
Default: 0.5
osd scrub priority
Description: The priority set for scrub operations. It is relative to osd client op priority.
Type: 32-bit Integer
Default: 5
Valid Range: 1-63
osd scrub chunk max
Description: The maximum number of object store chunks to scrub during single operation.
Type: 32-bit Integer
Default: 25
osd scrub chunk min
Description: The minimal number of object store chunks to scrub during single operation. Ceph blocks writes to single chunk during scrub.
[docs.ceph.com/docs/master/rados/configuration/osd-config-ref/](http://docs.ceph.com/docs/master/rados/configuration/osd-config-ref/)
Default: 5
osd deep scrub stride
Description: Read size when doing a deep scrub.
Type: 32-bit Integer
Default: 512 KB. 524288
osd scrub load threshold
Description: The normalized maximum load. Ceph will not scrub when the system load (as defined by getloadavg() / number of online cpus) is higher than this number. Default is 0.5.
Type: Float
Default: 0.5
osd scrub sleep
Description: Time to sleep before scrubbing next group of chunks. Increasing this value will slow down whole scrub operation while client operations will be less impacted.
Type: Float
Default: 0
SOURCES
http://docs.ceph.com/docs/master/rados/configuration/osd-config-ref/
https://github.com/ceph/ceph/blob/master/src/common/options.cc#L3130