Christian, et al:
Sorry for the lack of information. I wasn’t sure what of our hardware specifications or Ceph configuration was useful information at this point. Thanks for the feedback — any feedback, is appreciated at this point, as I’ve been beating my head against a wall trying to figure out what’s going on. (If anything. Maybe the spindle count is indeed our upper limit or our SSDs really suck? :-) )
To directly address your questions, see answers below:
- CBT is the Ceph Benchmarking Tool. Since my question was more generic rather than with CBT itself, it was probably more useful to post in the ceph-users list rather than cbt.
- 8 Cores are from 2x quad core Intel(R) Xeon(R) CPU E5-2609 0 @ 2.40GHz
- The SSDs are indeed Intel S3500s. I agree — not ideal, but supposedly capable of up to 75,000 random 4KB reads/writes. Throughput and longevity is quite low for an SSD, rated at about 400MB/s reads and 100MB/s writes, though. When we added these as journals in front of the SATA spindles, both VM performance and rados benchmark numbers were relatively unchanged.
- Regarding throughput vs iops, indeed — the throughput that I’m seeing is nearly worst case scenario, with all I/O being 4KB block size. With RBD cache enabled and the writeback option set in the VM configuration, I was hoping more coalescing would occur, increasing the I/O block size.
As an aside, the orchestration layer on top of KVM is OpenNebula if that’s of any interest.
VM information:
- Number = 15
- Worload = Mixed (I know, I know — that’s as vague of an answer as they come) A handful of VMs are running some MySQL databases and some web applications in Apache Tomcat. One is running a syslog server. Everything else is mostly static web page serving for a low number of users.
I can duplicate the blocked request issue pretty consistently, just by running something simple like a “yum -y update” in one VM. While that is running, ceph -w and ceph -s show the following:
root@dashboard:~# ceph -s
cluster f79d8c2a-3c14-49be-942d-83fc5f193a25
health HEALTH_WARN
1 requests are blocked > 32 sec
monmap e3: 3 mons at {storage-1=10.0.0.1:6789/0,storage-2=10.0.0.2:6789/0,storage-3=10.0.0.3:6789/0}
election epoch 136, quorum 0,1,2 storage-1,storage-2,storage-3
osdmap e75590: 6 osds: 6 up, 6 in
pgmap v3495103: 224 pgs, 1 pools, 826 GB data, 225 kobjects
2700 GB used, 2870 GB / 5571 GB avail
224 active+clean
client io 3292 B/s rd, 2623 kB/s wr, 81 op/s
2015-08-31 16:39:46.490696 mon.0 [INF] pgmap v3495096: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail
2015-08-31 16:39:47.789982 mon.0 [INF] pgmap v3495097: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 0 B/s rd, 517 kB/s wr, 130 op/s
2015-08-31 16:39:49.239033 mon.0 [INF] pgmap v3495098: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 0 B/s rd, 474 kB/s wr, 128 op/s
2015-08-31 16:39:51.970679 mon.0 [INF] pgmap v3495099: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 0 B/s rd, 58662 B/s wr, 22 op/s
2015-08-31 16:39:57.267697 mon.0 [INF] pgmap v3495100: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 11357 B/s wr, 5 op/s
2015-08-31 16:39:58.700312 mon.0 [INF] pgmap v3495101: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 1911 B/s rd, 701 kB/s wr, 19 op/s
2015-08-31 16:39:59.999624 mon.0 [INF] pgmap v3495102: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 4247 B/s rd, 3092 kB/s wr, 66 op/s
2015-08-31 16:40:02.156758 mon.0 [INF] pgmap v3495103: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 3292 B/s rd, 2623 kB/s wr, 81 op/s
2015-08-31 16:40:03.289101 mon.0 [INF] pgmap v3495104: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 65664 B/s rd, 2163 kB/s wr, 76 op/s
2015-08-31 16:40:04.679926 mon.0 [INF] pgmap v3495105: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 90075 B/s rd, 3158 kB/s wr, 34 op/s
2015-08-31 16:40:07.237293 mon.0 [INF] pgmap v3495106: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 0 B/s rd, 1899 kB/s wr, 29 op/s
2015-08-31 16:40:08.303615 mon.0 [INF] pgmap v3495107: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 259 kB/s rd, 2864 kB/s wr, 77 op/s
2015-08-31 16:40:09.352817 mon.0 [INF] pgmap v3495108: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 411 kB/s rd, 4093 kB/s wr, 115 op/s
2015-08-31 16:40:11.951104 mon.0 [INF] pgmap v3495109: 224 pgs: 224 active+clean; 826 GB data, 2700 GB used, 2870 GB / 5571 GB avail; 466 kB/s rd, 1863 kB/s wr, 148 op/s
I never seem to get anywhere near 300 op/s. If spindle count is indeed the problem, is there anything else I can do to improve caching or I/O coalescing to deal with my crippling IOP limit due to the low number of spindles?
Thanks,
--
Kenneth Van Alstyne
Systems Architect
Knight Point Systems, LLC
Service-Disabled Veteran-Owned Business
1775 Wiehle Avenue Suite 101 | Reston, VA 20190
c: 228-547-8045 f: 571-266-3106
www.knightpoint.com
DHS EAGLE II Prime Contractor: FC1 SDVOSB Track
GSA Schedule 70 SDVOSB: GS-35F-0646S
GSA MOBIS Schedule: GS-10F-0404Y
ISO 20000 / ISO 27001
Notice: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, copy, use, disclosure, or distribution is STRICTLY prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
> On Aug 31, 2015, at 11:01 AM, Christian Balzer <chibi@xxxxxxx> wrote:
>
>
> Hello,
>
> On Mon, 31 Aug 2015 08:31:57 -0500 Kenneth Van Alstyne wrote:
>
>> Sorry about the repost from the cbt list, but it was suggested I post
>> here as well:
>>
> I wasn't even aware a CBT (what the heck does that acronym stand for?)
> existed...
>
>> I am attempting to track down some performance issues in a Ceph cluster
>> recently deployed. Our configuration is as follows: 3 storage nodes,
> 3 nodes is, of course, bare minimum.
>
>> each with:
>> - 8 Cores
> Of what, apples? Detailed information makes for better replies.
>
>> - 64GB of RAM
> Ample.
>
>> - 2x 1TB 7200 RPM Spindle
> Even if your cores where to be rotten apple ones, that's very few
> spindles, so your CPU is unlikely to be the bottleneck.
>
>> - 1x 120GB Intel SSD
> Details, again. From your P.S. I conclude that these are S3500's,
> definitely not my choice for journals when it comes to speed and endurance.
>
>> - 2x 10GBit NICs (In LACP Port-channel)
> Massively overspec'ed considering your storage sinks/wells aka HDDs.
>
>>
>> The OSD pool min_size is set to “1” and “size” is set to “3”. When
>> creating a new pool and running RADOS benchmarks, performance isn’t bad
>> — about what I would expect from this hardware configuration:
>>
> Rados bench uses by default 4MB "blocks", which is the optimum size for
> (default) RBD pools.
> Bandwidth does not equal IOPS (which are commonly measured in 4KB blocks).
>
>> WRITES:
>> Total writes made: 207
>> Write size: 4194304
>> Bandwidth (MB/sec): 80.017
>>
>> Stddev Bandwidth: 34.9212
>> Max bandwidth (MB/sec): 120
>> Min bandwidth (MB/sec): 0
>> Average Latency: 0.797667
>> Stddev Latency: 0.313188
>> Max latency: 1.72237
>> Min latency: 0.253286
>>
>> RAND READS:
>> Total time run: 10.127990
>> Total reads made: 1263
>> Read size: 4194304
>> Bandwidth (MB/sec): 498.816
>>
>> Average Latency: 0.127821
>> Max latency: 0.464181
>> Min latency: 0.0220425
>>
>> This all looks fine, until we try to use the cluster for its purpose,
>> which is to house images for qemu-kvm, which are access using librbd.
> Not that it probably matters, but knowing if this Openstack, Ganeti or
> something else might be of interest.
>
>> I/O inside VMs have excessive I/O wait times (in the hundreds of ms at
>> times, making some operating systems, like Windows unusable) and
>> throughput struggles to exceed 10MB/s (or less). Looking at ceph
>> health, we see very low op/s numbers as well as throughput and the
>> requests blocked number seems very high. Any ideas as to what to look
>> at here?
>>
> Again, details.
>
> How many VMs?
> What are they doing?
> Keep in mind that the BEST sustained result you could hope for here
> (ignoring Ceph overhead and network latency) is the IOPS of 2 HDDs, so
> about 300 IOPS at best. TOTAL.
>
>> health HEALTH_WARN
>> 8 requests are blocked > 32 sec
>> monmap e3: 3 mons at
>> {storage-1=10.0.0.1:6789/0,storage-2=10.0.0.2:6789/0,storage-3=10.0.0.3:6789/0}
>> election epoch 128, quorum 0,1,2 storage-1,storage-2,storage-3 osdmap
>> e69615: 6 osds: 6 up, 6 in pgmap v3148541: 224 pgs, 1 pools, 819 GB
> 256 or 512 PGs would have been the "correct" number here, but that's of
> little importance.
>
>> data, 227 kobjects 2726 GB used, 2844 GB / 5571 GB avail
>> 224 active+clean
>> client io 3957 B/s rd, 3494 kB/s wr, 30 op/s
>>
> That's a lot of data being written for a tiny cluster like yours.
> Looking at your nodes with atop or similar tools will likely reveal that
> your HDDs are quite the busy beavers and can't keep up.
>
> Also prolonged values from "ceph -w" might be educational.
>
> Regards,
>
> Christian
>
>> Of note, on the other list, I was asked to provide the following:
>> - ceph version 0.94.1 (e4bfad3a3c51054df7e537a724c8d0bf9be972ff)
>> - The SSD is split into 8GB partitions. These 8GB partitions are
>> used as journal devices, specified in /etc/ceph/ceph.conf. For example:
>> [osd.0] host = storage-1
>> osd journal
>> = /dev/mapper/INTEL_SSDSC2BB120G4_CVWL4363006R120LGNp1
>> - rbd_cache is enabled and qemu cache is set to “writeback"
>> - rbd_concurrent_management_ops is unset, so it appears the
>> default is “10”
>>
>> Thanks,
>>
>> --
>> Kenneth Van Alstyne
>> Systems Architect
>> Knight Point Systems, LLC
>> Service-Disabled Veteran-Owned Business
>> 1775 Wiehle Avenue Suite 101 | Reston, VA 20190
>> c: 228-547-8045 f: 571-266-3106
>> www.knightpoint.com
>> DHS EAGLE II Prime Contractor: FC1 SDVOSB Track
>> GSA Schedule 70 SDVOSB: GS-35F-0646S
>> GSA MOBIS Schedule: GS-10F-0404Y
>> ISO 20000 / ISO 27001
>>
>> Notice: This e-mail message, including any attachments, is for the sole
>> use of the intended recipient(s) and may contain confidential and
>> privileged information. Any unauthorized review, copy, use, disclosure,
>> or distribution is STRICTLY prohibited. If you are not the intended
>> recipient, please contact the sender by reply e-mail and destroy all
>> copies of the original message.
>>
>
>
> --
> Christian Balzer Network/Systems Engineer
> chibi@xxxxxxx Global OnLine Japan/Fusion Communications
> http://www.gol.com/
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
