During a recent snafu with a production cluster I disabled scrubbing and deep 
scrubbing in order to reduce load on the cluster while things backfilled and 
settled down.  The PTSD caused by the incident meant I was not keen to 
re-enable it until I was confident we had fixed the root cause of the issues 
(driver issues with a new NIC type introduced with new hardware that did not 
show up until production load hit them).   My cluster is using Jewel 10.2.1, 
and is a mix of SSD and SATA over 20 hosts, 352 OSDs in total.

Fast forward a few weeks and I was ready to re-enable it.  On some reading I 
was concerned the cluster might kick off excessive scrubbing once I unset the 
flags, so I tried increasing the deep scrub interval from 7 days to 60 days - 
with most of the last deep scrubs being from over a month before I was hoping 
it would distribute them over the next 30 days.  Having unset the flag and 
carefully watched the cluster it seems to have just run a steady catch up 
without significant impact.  What I am noticing though is that the scrubbing is 
seeming to just run through the full set of PGs, so it did some 2280 PGs last 
night over 6 hours, and so far today in 12 hours another 4000 odd.  With 13408 
PGs, I am guessing that all this will stop some time early tomorrow.

ceph-glb-fec-01[/var/log]$ sudo ceph pg dump|awk '{print $20}'|grep 
2017|sort|uniq -c
dumped all in format plain
      5 2017-05-23
     18 2017-05-24
     33 2017-05-25
     52 2017-05-26
     89 2017-05-27
    114 2017-05-28
    144 2017-05-29
    172 2017-05-30
    256 2017-05-31
    191 2017-06-01
    230 2017-06-02
    369 2017-06-03
    606 2017-06-04
    680 2017-06-05
    919 2017-06-06
   1261 2017-06-07
   1876 2017-06-08
     15 2017-06-09
   2280 2017-07-05
   4098 2017-07-06

My concern is am I now set to have all 13408 PGs do a deep scrub in 60 days in 
a serial fashion again over 3 days.  I would much rather they distribute over 
that period.

Will the OSDs do this distribution themselves now they have caught up, or do I 
need to say create a script that will trigger batches of PGs to deep scrub over 
time to push out the distribution again?





Adrian Saul | Infrastructure Projects Team Lead
IT
T 02 9009 9041 | M +61 402 075 760
30 Ross St, Glebe NSW 2037
adrian.s...@tpgtelecom.com.au<mailto:adrian.s...@tpgtelecom.com.au> | 
www.tpg.com.au<http://www.tpg.com.au/>

TPG Telecom (ASX: TPM)


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