>-----Original Message----- >From: ceph-users-boun...@lists.ceph.com [mailto:ceph-users- >boun...@lists.ceph.com] On Behalf Of Mark Nelson >Sent: Monday, February 03, 2014 6:48 PM >To: ceph-users@lists.ceph.com >Subject: Re: [ceph-users] Low RBD Performance > >On 02/03/2014 07:29 PM, Gruher, Joseph R wrote: >> Hi folks- >> >> I'm having trouble demonstrating reasonable performance of RBDs. I'm >> running Ceph 0.72.2 on Ubuntu 13.04 with the 3.12 kernel. I have four >> dual-Xeon servers, each with 24GB RAM, and an Intel 320 SSD for >> journals and four WD 10K RPM SAS drives for OSDs, all connected with >> an LSI 1078. This is just a lab experiment using scrounged hardware >> so everything isn't sized to be a Ceph cluster, it's just what I have >> lying around, but I should have more than enough CPU and memory >resources. >> Everything is connected with a single 10GbE. >> >> When testing with RBDs from four clients (also running Ubuntu 13.04 >> with >> 3.12 kernel) I am having trouble breaking 300 IOPS on a 4KB random >> read or write workload (cephx set to none, replication set to one). >> IO is generated using FIO from four clients, each hosting a single 1TB >> RBD, and I've experimented with queue depths and increasing the number >> of RBDs without any benefit. 300 IOPS for a pool of 16 10K RPM HDDs >> seems quite low, not to mention the journal should provide a good >> boost on write workloads. When I run a 4KB object write workload in >> Cosbench I can approach 3500 Obj/Sec which seems more reasonable. >> >> Sample FIO configuration: >> >> [global] >> >> ioengine=libaio >> >> direct=1 >> >> ramp_time=300 >> >> runtime=300 >> >> [4k-rw] >> >> description=4k-rw >> >> filename=/dev/rbd1 >> >> rw=randwrite >> >> bs=4k >> >> stonewall >> >> I use --iodepth=X on the FIO command line to set the queue depth when >> testing. >> >> I notice in the FIO output despite the iodepth setting it seems to be >> reporting an IO depth of only 1, which would certainly help explain >> poor performance, but I'm at a loss as to why, I wonder if it could be >> something specific to RBD behavior, like I need to use a different IO >> engine to establish queue depth. >> >> IO depths : 1=200.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >>=64=0.0% >> >> Any thoughts appreciated! > >Interesting results with the io depth at 1. I Haven't seen that behaviour when >using libaio, direct=1, and higher io depths. Is this kernel RBD or QEMU/KVM? >If it's QEMU/KVM, is it the libvirt driver? > >Certainly 300 IOPS is low for that kind of setup compared to what we've seen >for RBD on other systems (especially with 1x replication). Given that you are >seeing more reasonable performance with RGW, I guess I'd look at a couple >things: > >- Figure out why fio is reporting queue depth = 1
Yup, I agree, I will work on this and report back. First thought is to try specifying the queue depth in the FIO workload file instead of on the command line. >- Does increasing the num jobs help (ie get concurrency another way)? I will give this a shot. >- Do you have enough PGs in the RBD pool? I should, for 16 OSDs and no replication I use 2048 PGs/PGPs (100 * 16 / 1 rounded up to power of 2). >- Are you using the virtio driver if QEMU/KVM? No virtualization, clients are bare metal using kernel RBD. _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
