From mboxrd@z Thu Jan 1 00:00:00 1970 From: Malcolm Haak Subject: Re: RBD Read performance Date: Fri, 19 Apr 2013 12:21:18 +1000 Message-ID: <5170AA1E.10506@sgi.com> References: <516F77FF.4060401@sgi.com> <516F9AEB.7000706@inktank.com> <516F9F35.1030507@sgi.com> <51708F80.8090803@sgi.com> <51709278.8050602@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from relay1.sgi.com ([192.48.179.29]:50803 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967156Ab3DSCVY (ORCPT ); Thu, 18 Apr 2013 22:21:24 -0400 In-Reply-To: <51709278.8050602@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Mark Nelson Cc: ceph-devel@vger.kernel.org Ok this is getting interesting. rados -p bench 300 write --no-cleanup Total time run: 301.103933 Total writes made: 22477 Write size: 4194304 Bandwidth (MB/sec): 298.595 Stddev Bandwidth: 171.941 Max bandwidth (MB/sec): 832 Min bandwidth (MB/sec): 8 Average Latency: 0.214295 Stddev Latency: 0.405511 Max latency: 3.26323 Min latency: 0.019429 rados -p bench 300 seq Total time run: 76.634659 Total reads made: 22477 Read size: 4194304 Bandwidth (MB/sec): 1173.203 Average Latency: 0.054539 Max latency: 0.937036 Min latency: 0.018132 So the writes on the rados bench are slower than we have achieved with dd and were slower on the back-end file store as well. But the reads are great. We could see 1~1.5GB/s on the back-end as well. So we started doing some other tests to see if it was in RBD or the VFS layer in the kernel.. And things got weird. So using CephFS: root@dogbreath ~]# dd if=/dev/zero of=/test-fs/DELETEME1 bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 7.28658 s, 1.5 GB/s [root@dogbreath ~]# dd if=/dev/zero of=/test-fs/DELETEME1 bs=1G count=20 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 20.6105 s, 1.0 GB/s [root@dogbreath ~]# dd if=/dev/zero of=/test-fs/DELETEME1 bs=1G count=40 40+0 records in 40+0 records out 42949672960 bytes (43 GB) copied, 53.4013 s, 804 MB/s [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=4 iflag=direct 4+0 records in 4+0 records out 4294967296 bytes (4.3 GB) copied, 23.1572 s, 185 MB/s [root@dogbreath ~]# [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=4 4+0 records in 4+0 records out 4294967296 bytes (4.3 GB) copied, 1.20258 s, 3.6 GB/s [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=20 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 5.40589 s, 4.0 GB/s [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=40 40+0 records in 40+0 records out 42949672960 bytes (43 GB) copied, 10.4781 s, 4.1 GB/s [root@dogbreath ~]# echo 1 > /proc/sys/vm/drop_caches [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=40 ^C24+0 records in 23+0 records out 24696061952 bytes (25 GB) copied, 56.8824 s, 434 MB/s [root@dogbreath ~]# dd if=/test-fs/DELETEME1 of=/dev/null bs=1G count=40 40+0 records in 40+0 records out 42949672960 bytes (43 GB) copied, 113.542 s, 378 MB/s [root@dogbreath ~]# So about the same, when we were not hitting cache. So we decided to just hit the RBD block device with no FS on it.. Welcome to weirdsville root@ty3:~# umount /test-rbd-fs root@ty3:~# root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=4 4+0 records in 4+0 records out 4294967296 bytes (4.3 GB) copied, 18.6603 s, 230 MB/s root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=4 iflag=direct 4+0 records in 4+0 records out 4294967296 bytes (4.3 GB) copied, 1.13584 s, 3.8 GB/s root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=20 iflag=direct 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 4.61028 s, 4.7 GB/s root@ty3:~# echo 1 > /proc/sys/vm/drop_caches root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=20 iflag=direct 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 4.43416 s, 4.8 GB/s root@ty3:~# echo 1 > /proc/sys/vm/drop_caches root@ty3:~# root@ty3:~# root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=20 iflag=direct 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 5.07426 s, 4.2 GB/s root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=40 iflag=direct 40+0 records in 40+0 records out 42949672960 bytes (43 GB) copied, 8.60885 s, 5.0 GB/s root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=80 iflag=direct 80+0 records in 80+0 records out 85899345920 bytes (86 GB) copied, 18.4305 s, 4.7 GB/s root@ty3:~# dd if=/dev/rbd1 of=/dev/null bs=1G count=20 20+0 records in 20+0 records out 21474836480 bytes (21 GB) copied, 91.5546 s, 235 MB/s root@ty3:~# So.. we just started reading from the block device. And the numbers were well.. Faster than the QDR IB can do TCP/IP. So we figured local caching. So we dropped caches and ramped up to bigger than ram. (ram is 24GB) and it got faster. So we went to 3x ram.. and it was a bit slower.. Oh also the whole time we were doing these tests, the back-end disk was seeing no I/O at all.. We were dropping caches on the OSD's as well, but even if it was caching at the OSD end, the IB link is only QDR and we aren't doing RDMA so. Yeah..No idea what is going on here... On 19/04/13 10:40, Mark Nelson wrote: > On 04/18/2013 07:27 PM, Malcolm Haak wrote: >> Morning all, >> >> Did the echos on all boxes involved... and the results are in.. >> >> [root@dogbreath ~]# >> [root@dogbreath ~]# dd if=/test-rbd-fs/DELETEME of=/dev/null bs=4M >> count=10000 iflag=direct >> 10000+0 records in >> 10000+0 records out >> 41943040000 bytes (42 GB) copied, 144.083 s, 291 MB/s >> [root@dogbreath ~]# dd if=/test-rbd-fs/DELETEME of=/dev/null bs=4M >> count=10000 >> 10000+0 records in >> 10000+0 records out >> 41943040000 bytes (42 GB) copied, 316.025 s, 133 MB/s >> [root@dogbreath ~]# > > Boo! > >> >> No change which is a shame. What other information or testing should I >> start? > > Any chance you can try out a quick rados bench test from the client > against the pool for writes and reads and see how that works? > > rados -p bench 300 write --no-cleanup > rados -p bench 300 seq > >> >> Regards >> >> Malcolm Haak >> >> On 18/04/13 17:22, Malcolm Haak wrote: >>> Hi Mark! >>> >>> Thanks for the quick reply! >>> >>> I'll reply inline below. >>> >>> On 18/04/13 17:04, Mark Nelson wrote: >>>> On 04/17/2013 11:35 PM, Malcolm Haak wrote: >>>>> Hi all, >>>> >>>> Hi Malcolm! >>>> >>>>> >>>>> I jumped into the IRC channel yesterday and they said to email >>>>> ceph-devel. I have been having some read performance issues. With >>>>> Reads >>>>> being slower than writes by a factor of ~5-8. >>>> >>>> I recently saw this kind of behaviour (writes were fine, but reads were >>>> terrible) on an IPoIB based cluster and it was caused by the same TCP >>>> auto tune issues that Jim Schutt saw last year. It's worth a try at >>>> least to see if it helps. >>>> >>>> echo "0" > /proc/sys/net/ipv4/tcp_moderate_rcvbuf >>>> >>>> on all of the clients and server nodes should be enough to test it out. >>>> Sage added an option in more recent Ceph builds that lets you work >>>> around it too. >>>> >>> Awesome I will test this first up tomorrow. >>>>> >>>>> First info: >>>>> Server >>>>> SLES 11 SP2 >>>>> Ceph 0.56.4. >>>>> 12 OSD's that are Hardware Raid 5 each of the twelve is made from 5 >>>>> NL-SAS disks for a total of 60 disks (Each lun can do around 320MB/s >>>>> stream write and the same if not better read) Connected via 2xQDR IB >>>>> OSD's/MDS and such all on same box (for testing) >>>>> Box is a Quad AMD Opteron 6234 >>>>> Ram is 256Gb >>>>> 10GB Journals >>>>> osd_op_theads: 8 >>>>> osd_disk_threads:2 >>>>> Filestore_op_threads:4 >>>>> OSD's are all XFS >>>> >>>> Interesting setup! QUAD socket Opteron boxes have somewhat slow and >>>> slightly oversubscribed hypertransport links don't they? I wonder >>>> if on >>>> a system with so many disks and QDR-IB if that could become a >>>> problem... >>>> >>>> We typically like smaller nodes where we can reasonably do 1 OSD per >>>> drive, but we've tested on a couple of 60 drive chassis in RAID configs >>>> too. Should be interesting to hear what kind of aggregate performance >>>> you can eventually get. >>> >>> We are also going to try this out with 6 luns on a dual xeon box. The >>> Opteron box was the biggest scariest thing we had that was doing >>> nothing. >>> >>>> >>>>> >>>>> All nodes are connected via QDR IB using IP_O_IB. We get 1.7GB/s on >>>>> TCP >>>>> performance tests between the nodes. >>>>> >>>>> Clients: One is FC17 the other us Ubuntu 12.10 they only have around >>>>> 32GB-70GB ram. >>>>> >>>>> We ran into an odd issue were the OSD's would all start in the same >>>>> NUMA >>>>> node and pretty much on the same processor core. We fixed that up with >>>>> some cpuset magic. >>>> >>>> Strange! Was that more due to cpuset or Ceph? I can't imagine that we >>>> are doing anything that would cause that. >>>> >>> >>> More than likely it is an odd quirk in the SLES kernel.. but when I have >>> time I'll do some more poking. We were seeing insane CPU usage on some >>> cores because all the OSD's were piled up in one place. >>> >>>>> >>>>> Performance testing we have done: (Note oflag=direct was yielding >>>>> results within 5% of cached results) >>>>> >>>>> >>>>> root@ty3:~# dd if=/dev/zero of=/test-rbd-fs/DELETEME bs=10M count=3200 >>>>> 3200+0 records in >>>>> 3200+0 records out >>>>> 33554432000 bytes (34 GB) copied, 47.6685 s, 704 MB/s >>>>> root@ty3:~# >>>>> root@ty3:~# rm /test-rbd-fs/DELETEME >>>>> root@ty3:~# >>>>> root@ty3:~# dd if=/dev/zero of=/test-rbd-fs/DELETEME bs=10M count=4800 >>>>> 4800+0 records in >>>>> 4800+0 records out >>>>> 50331648000 bytes (50 GB) copied, 69.5527 s, 724 MB/s >>>>> >>>>> [root@dogbreath ~]# dd of=/test-rbd-fs/DELETEME if=/dev/zero bs=10M >>>>> count=2400 >>>>> 2400+0 records in >>>>> 2400+0 records out >>>>> 25165824000 bytes (25 GB) copied, 26.3593 s, 955 MB/s >>>>> [root@dogbreath ~]# rm -f /test-rbd-fs/DELETEME >>>>> [root@dogbreath ~]# dd of=/test-rbd-fs/DELETEME if=/dev/zero bs=10M >>>>> count=9600 >>>>> 9600+0 records in >>>>> 9600+0 records out >>>>> 100663296000 bytes (101 GB) copied, 145.212 s, 693 MB/s >>>>> >>>>> Both clients each doing a 140GB write (2x dogbreath's RAM) at the same >>>>> time to two different rbds in the same pool. >>>>> >>>>> root@ty3:~# rm /test-rbd-fs/DELETEME >>>>> root@ty3:~# dd if=/dev/zero of=/test-rbd-fs/DELETEME bs=10M >>>>> count=14000 >>>>> 14000+0 records in >>>>> 14000+0 records out >>>>> 146800640000 bytes (147 GB) copied, 412.404 s, 356 MB/s >>>>> root@ty3:~# >>>>> >>>>> [root@dogbreath ~]# rm -f /test-rbd-fs/DELETEME >>>>> [root@dogbreath ~]# dd of=/test-rbd-fs/DELETEME if=/dev/zero bs=10M >>>>> count=14000 >>>>> 14000+0 records in >>>>> 14000+0 records out >>>>> 146800640000 bytes (147 GB) copied, 433.351 s, 339 MB/s >>>>> [root@dogbreath ~]# >>>>> >>>>> Onto reads... >>>>> Also we found that doing iflag=direct increased read performance. >>>>> >>>>> [root@dogbreath ~]# dd of=/dev/null if=/test-rbd-fs/DELETEME bs=10M >>>>> count=160 >>>>> 160+0 records in >>>>> 160+0 records out >>>>> 1677721600 bytes (1.7 GB) copied, 29.4242 s, 57.0 MB/s >>>>> [root@dogbreath ~]# >>>>> [root@dogbreath ~]# echo 1 > /proc/sys/vm/drop_caches >>>>> [root@dogbreath ~]# dd if=/test-rbd-fs/DELETEME of=/dev/null bs=4M >>>>> count=10000 >>>>> 10000+0 records in >>>>> 10000+0 records out >>>>> 41943040000 bytes (42 GB) copied, 382.334 s, 110 MB/s >>>>> [root@dogbreath ~]# >>>>> [root@dogbreath ~]# echo 1 > /proc/sys/vm/drop_caches >>>>> [root@dogbreath ~]# dd if=/test-rbd-fs/DELETEME of=/dev/null bs=4M >>>>> count=10000 iflag=direct >>>>> 10000+0 records in >>>>> 10000+0 records out >>>>> 41943040000 bytes (42 GB) copied, 150.774 s, 278 MB/s >>>>> [root@dogbreath ~]# >>>>> >>>>> >>>>> So what info do you want/where do I start hunting for my wumpus? >>>> >>>> might also be worth looking at the size of the reads to see if >>>> there's a >>>> lot of fragmentation. Also, is this kernel rbd or qemu-kvm? >>>> >>> >>> Thing that got us was the back-end storage was showing very low read >>> rates. Where as when writing we could see almost a 2xWrite rate back to >>> physical disk (we assume that is Journal+data as the 2x is not from the >>> word go but ramps up around the 3-5 second mark) >>> >>> It is kernel rbd at the moment, we will be testing qemu-kvm after things >>> make sense. >>> >>>>> >>>>> Regards >>>>> >>>>> Malcolm Haak >>>>> >>>>> >>>>> -- >>>>> To unsubscribe from this list: send the line "unsubscribe >>>>> ceph-devel" in >>>>> the body of a message to majordomo@vger.kernel.org >>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >