On Mar 14, 2012, at 4:28 AM, madhusudhana wrote: > João Eduardo Luís <jecluis <at> gmail.com> writes: > >> >> On 03/13/2012 10:39 AM, madhusudhana wrote: >>> Hi all, >>> Can someone PLEASE help me to understand why data copying (simple cp >>> or rsync) is SO slow in CEPH ? And delete command (\rm -rf) for removing >>> a small (175M) directory is taking so much of time. Because of this, >>> i am not able to complete evaluation of ceph using my actual workload. >>> >>> I am hereby requesting all to help me in finding out the reason for >>> slow write/delete in my ceph cluster. I am really trying hard to >>> complete the evaluation with actual workload but not able to copy the >>> data whats required for evaluation to ceph cluster bcz of slow copy. >>> >>> I really appreciate any help on this. >>> >>> Thanks in advance >>> Madhusudhan >>> >> >> Hi Madhusudhan, >> >> Are you using Btrfs? And are you taking snapshots while you're >> performing those operations? >> > Joao, > Yes. all my OSD's are running on btrfs. I am not doing anything special > except running 'cp' or 'rsync' command. can you please let me know how > i can find if am taking snapshots while I do 'cp' or 'rsync' commands ? I am yet to fully understand Ceph's behavior, thus you should not take my word on it, but I believe Ceph will automatically take snapshots as a checkpointing mechanism. So, until someone (*looks at Sage*) declares I am completely and utterly wrong, I'm going with that assumption. Also, I am not sure if the slowdown you're suffering is Btrfs-related, but just in case... > > One more concern is 'rm' command is also TOO slow. I am a newbie here and > i don't know to much about ceph working. I configured it in a simple way. > Install ceph and run mkcephfs and start ceph in all the servers in the > cluster. > > I want to understand why basic operations like 'cp' and 'rm' are slow bcz > my actual workload does a lot of copy and delete operation. If I find the > reason for the slowness and get a fix, then I think i can better compare and > complete my ceph evaluation. My follow up questions: - Are you copying into Ceph? From within Ceph, into Ceph? Or are you simply copying from Ceph to somewhere else? - Under which conditions do these slowdowns happen? Are you performing *a lot* of cp's / rm's in a short amount of time? Cheers, Joao --- João Eduardo Luís gpg key: 477C26E5 from pool.keyserver.eu
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