Re: Rebalance/Backfill Throtling - anything missing here?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Another question - I mentioned here 37% of objects being moved arround - this is MISPLACED object (degraded objects were 0.001%, after I removed 1 OSD from cursh map (out of 44 OSD or so).

Can anybody confirm this is normal behaviour - and are there any workarrounds ?

I understand this is because of the object placement algorithm of CEPH, but still 37% of object missplaces just by removing 1 OSD from crush maps out of 44 make me wonder why this large percentage ?

Seems not good to me, and I have to remove another 7 OSDs (we are demoting some old hardware nodes). This means I can potentialy go with 7 x the same number of missplaced objects...?

Any thoughts ?

Thanks

On 3 March 2015 at 12:14, Andrija Panic <andrija.panic@xxxxxxxxx> wrote:
Thanks Irek.

Does this mean, that after peering for each PG, there will be delay of 10sec, meaning that every once in a while, I will have 10sec od the cluster NOT being stressed/overloaded, and then the recovery takes place for that PG, and then another 10sec cluster is fine, and then stressed again ?

I'm trying to understand process before actually doing stuff (config reference is there on ceph.com but I don't fully understand the process)

Thanks,
Andrija

On 3 March 2015 at 11:32, Irek Fasikhov <malmyzh@xxxxxxxxx> wrote:
Hi.

Use value "osd_recovery_delay_start"
example:
[root@ceph08 ceph]# ceph --admin-daemon /var/run/ceph/ceph-osd.94.asok config show  | grep osd_recovery_delay_start
  "osd_recovery_delay_start": "10"

2015-03-03 13:13 GMT+03:00 Andrija Panic <andrija.panic@xxxxxxxxx>:
HI Guys,

I yesterday removed 1 OSD from cluster (out of 42 OSDs), and it caused over 37% od the data to rebalance - let's say this is fine (this is when I removed it frm Crush Map).

I'm wondering - I have previously set some throtling mechanism, but during first 1h of rebalancing, my rate of recovery was going up to 1500 MB/s - and VMs were unusable completely, and then last 4h of the duration of recover this recovery rate went down to, say, 100-200 MB.s and during this VM performance was still pretty impacted, but at least I could work more or a less

So my question, is this behaviour expected, is throtling here working as expected, since first 1h was almoust no throtling applied if I check the recovery rate 1500MB/s and the impact on Vms.
And last 4h seemed pretty fine (although still lot of impact in general)

I changed these throtling on the fly with:

ceph tell osd.* injectargs '--osd_recovery_max_active 1'
ceph tell osd.* injectargs '--osd_recovery_op_priority 1'
ceph tell osd.* injectargs '--osd_max_backfills 1'

My Jorunals are on SSDs (12 OSD per server, of which 6 journals on one SSD, 6 journals on another SSD)  - I have 3 of these hosts.

Any thought are welcome.
--

Andrija Panić

_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com




--
С уважением, Фасихов Ирек Нургаязович
Моб.: +79229045757



--

Andrija Panić



--

Andrija Panić
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

[Index of Archives]     [Information on CEPH]     [Linux Filesystem Development]     [Ceph Development]     [Ceph Large]     [Ceph Dev]     [Linux USB Development]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [xfs]


  Powered by Linux