In my case we have 72 OSDs. We are experiencing some performance issues. We
believe that the reason is the scrubbing, so we want to turn scrubbing off for
a few days.
Given the default parameters of 1 day for scrub and 7 days for deep scrub. We
turn off scrub for let's say 6 days, then when we turn it on will it try to do
all the scrubbing that were supposed to be done in those days when it was
turned off?
Kind regards,
Laszlo
On 08.03.2017 12:51, Peter Maloney wrote:
It will stick to the config. If you limit the amount of work scrub does
at a time, then you can let it do whatever it wants without issues
(except 10.2.x which had a bug fixed in 10.2.4, but skip to 10.2.5 to
fix a regression).
For example:
# less scrub work at a time, with delay
osd scrub chunk min = 1 # default 5
osd scrub chunk max = 1 # default 25
osd scrub sleep = 0.5 # default 0
# lower scrub priority (possibly no effect since Jewel)
osd disk thread ioprio class = idle
osd disk thread ioprio priority = 3
And this is already default:
osd deep scrub stride = 524288 # 512 KiB
osd max scrubs = 1
And I set this, but not recommending it. The reason I post it here is
just to show that the above is slowed down enough that everything is
scrubbed within this long scrub interval, but might need adjustment for
a more normal setting here:
# 60 days ... default is 7 days
osd deep scrub interval = 5259488
And more inline answers below
On 03/08/17 10:46, Laszlo Budai wrote:
Hello,
is there any risk related to cluster overload when the scrub is re
enabled after a certain amount of time being disabled?
I am thinking of the following scenario:
1. scrub/deep scrub are disabled.
2. after a while (few days) we re enable them. How will the cluster
perform?
should be as normal during normal scrubbing... just no/short breaks in
between. (use osd scrub sleep for this)
Will it run all the scrub jobs that were supposed to be running in the
meantime, or it will just start scheduling scrub jobs according to the
scrub related parameters?
It will run them 1 at a time, or however you have configured it, until
all are within the target time range. Why shouldn't it obey its config?
And maybe as a side effect, the next time they are scrubbed will also be
timed closely together too.
Can you point me to some documentation about this topic?
Nothing interesting with descriptions, just the reference manual for the
options listed above. Someone on IRC gave me the above options and I
tested and fiddled with them to see how ceph behaves.
Thank you,
Laszlo
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