Help for Ceph Scrub / Performance

Y

yena

Renowned Member
Nov 18, 2011
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Hello,
i'm testing a Ceph cluster and i notice low performance when it enter in
"active+clean+scrubbing+deep" state

Reading this, may be a solution:
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http://sudomakeinstall.com/linux-systems/ceph-scrubbing

Inject the new settings for the existing OSD:
ceph tell osd.* injectargs '--osd_disk_thread_ioprio_priority 7'
ceph tell osd.* injectargs '--osd_disk_thread_ioprio_class idle'

Edit your ceph.conf on your storage nodes to automatically set the the priority at runtime.
#Reduce impact of scrub.
osd_disk_thread_ioprio_class = "idle"
osd_disk_thread_ioprio_priority = 7
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Some one have the same problem ?
Thanks
 
Hi,

my small home lab cluster of three nodes with one hdd osd in each is currently deep scrubbing (there was a problem that kept CEPH from working for a week while I was away on vacation and now there seems to be a backlog) and performance has gone way down (IO delay is higher than the low CPU load).

I am aware that such a small cluster with so few hdd osds will always be slow. But the scrubbing is really a hit on performance.

Now I am wondering what I can do to improve performance:

- Would more drives help or would they all be similarly under pressure when scrubbing (I assume this is a pool wide operation)?
- Would more pools help? Probably not, as I assume scrubbing concerns the entire pool and with all VMs in one pool, they would all be affected.

So probably my best bet is to add another pool (this time with ssds) and move my VMs there (and only keep the data volumes on the hdd pool).

What are the thoughts of people who (unlike me) know what they are doing?

Thanks
 
Oh, and is there a way to tell how much longer (deep) scrubbing is going to take? (For rebalancing there was a "time left" info)
 
So, um, is there a way to predict how long scrubbing is going to take? I am sitting here again, waiting for scrubbing to complete in order to replace a disk (not due to failure but to increase capacity)...
 
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