Re: Extreme slowness in SSD cluster with 3 nodes and 9 OSD with 3.16-3 kernel

[mad Engineer <themadengin33r@xxxxxxxxx>]

reinstalled ceph packages and now with memstore backend [osd objectstore =memstore] its giving 400Kbps .No idea where the problem is.

On Sun, Mar 1, 2015 at 12:30 AM, mad Engineer <themadengin33r@xxxxxxxxx> wrote:

tried changing scheduler from deadline to noop also upgraded to Gaint and btrfs filesystem,downgraded kernel to 3.16 from 3.16-3 not much difference

dd if=/dev/zero of=hi bs=4k count=25000 oflag=direct

25000+0 records in

25000+0 records out

102400000 bytes (102 MB) copied, 94.691 s, 1.1 MB/s

Earlier on a vmware setup i was getting ~850 KBps and now even on physical server with SSD drives its just over 1MBps.I doubt some serious configuration issues.

Tried iperf between 3 servers all are showing 9 Gbps,tried icmp with different packet size ,no fragmentation.

i also noticed that out of 9 osd 5 are 850 EVO and 4 are 840 EVO.I believe this will not cause this much drop in performance.

Thanks for any help

 

On Sat, Feb 28, 2015 at 6:49 PM, Alexandre DERUMIER <aderumier@xxxxxxxxx> wrote:

As optimisation,

try to set ioscheduler to noop,

and also enable rbd_cache=true. (It's really helping for for sequential writes)

but your results seem quite low, 926kb/s with 4k, it's only 200io/s.

check if you don't have any big network latencies, or mtu fragementation problem.

Maybe also try to bench with fio, with more parallel jobs.




----- Mail original -----
De: "mad Engineer" <themadengin33r@xxxxxxxxx>
À: "Philippe Schwarz" <phil@xxxxxxxxxxxxxx>
Cc: "ceph-users" <ceph-users@xxxxxxxxxxxxxx>
Envoyé: Samedi 28 Février 2015 13:06:59
Objet: Re: Extreme slowness in SSD cluster with 3 nodes and 9 OSD with 3.16-3 kernel

Thanks for the reply Philippe,we were using these disks in our NAS,now
it looks like i am in big trouble :-(

On Sat, Feb 28, 2015 at 5:02 PM, Philippe Schwarz <phil@xxxxxxxxxxxxxx> wrote:
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> Le 28/02/2015 12:19, mad Engineer a écrit :
>> Hello All,
>>
>> I am trying ceph-firefly 0.80.8
>> (69eaad7f8308f21573c604f121956e64679a52a7) with 9 OSD ,all Samsung
>> SSD 850 EVO on 3 servers with 24 G RAM,16 cores @2.27 Ghz Ubuntu
>> 14.04 LTS with 3.16-3 kernel.All are connected to 10G ports with
>> maximum MTU.There are no extra disks for journaling and also there
>> are no separate network for replication and data transfer.All 3
>> nodes are also hosting monitoring process.Operating system runs on
>> SATA disk.
>>
>> When doing a sequential benchmark using "dd" on RBD, mounted on
>> client as ext4 its taking 110s to write 100Mb data at an average
>> speed of 926Kbps.
>>
>> time dd if=/dev/zero of=hello bs=4k count=25000 oflag=direct
>> 25000+0 records in 25000+0 records out 102400000 bytes (102 MB)
>> copied, 110.582 s, 926 kB/s
>>
>> real 1m50.585s user 0m0.106s sys 0m2.233s
>>
>> While doing this directly on ssd mount point shows:
>>
>> time dd if=/dev/zero of=hello bs=4k count=25000 oflag=direct
>> 25000+0 records in 25000+0 records out 102400000 bytes (102 MB)
>> copied, 1.38567 s, 73.9 MB/s
>>
>> OSDs are in XFS with these extra arguments :
>>
>> rw,noatime,inode64,logbsize=256k,delaylog,allocsize=4M
>>
>> ceph.conf
>>
>> [global] fsid = 7d889081-7826-439c-9fe5-d4e57480d9be
>> mon_initial_members = ceph1, ceph2, ceph3 mon_host =
>> 10.99.10.118,10.99.10.119,10.99.10.120 auth_cluster_required =
>> cephx auth_service_required = cephx auth_client_required = cephx
>> filestore_xattr_use_omap = true osd_pool_default_size = 2
>> osd_pool_default_min_size = 2 osd_pool_default_pg_num = 450
>> osd_pool_default_pgp_num = 450 max_open_files = 131072
>>
>> [osd] osd_mkfs_type = xfs osd_op_threads = 8 osd_disk_threads = 4
>> osd_mount_options_xfs =
>> "rw,noatime,inode64,logbsize=256k,delaylog,allocsize=4M"
>>
>>
>> on our traditional storage with Full SAS disk, same "dd" completes
>> in 16s with an average write speed of 6Mbps.
>>
>> Rados bench:
>>
>> rados bench -p rbd 10 write Maintaining 16 concurrent writes of
>> 4194304 bytes for up to 10 seconds or 0 objects Object prefix:
>> benchmark_data_ceph1_2977 sec Cur ops started finished avg MB/s
>> cur MB/s last lat avg lat 0 0 0 0
>> 0 0 - 0 1 16 94 78
>> 311.821 312 0.041228 0.140132 2 16 192 176
>> 351.866 392 0.106294 0.175055 3 16 275 259
>> 345.216 332 0.076795 0.166036 4 16 302 286
>> 285.912 108 0.043888 0.196419 5 16 395 379
>> 303.11 372 0.126033 0.207488 6 16 501 485
>> 323.242 424 0.125972 0.194559 7 16 621 605
>> 345.621 480 0.194155 0.183123 8 16 730 714
>> 356.903 436 0.086678 0.176099 9 16 814 798
>> 354.572 336 0.081567 0.174786 10 16 832
>> 816 326.313 72 0.037431 0.182355 11 16 833
>> 817 297.013 4 0.533326 0.182784 Total time run:
>> 11.489068 Total writes made: 833 Write size:
>> 4194304 Bandwidth (MB/sec): 290.015
>>
>> Stddev Bandwidth: 175.723 Max bandwidth (MB/sec): 480 Min
>> bandwidth (MB/sec): 0 Average Latency: 0.220582 Stddev
>> Latency: 0.343697 Max latency: 2.85104 Min
>> latency: 0.035381
>>
>> Our ultimate aim is to replace existing SAN with ceph,but for that
>> it should meet minimum 8000 iops.Can any one help me with this,OSD
>> are SSD,CPU has good clock speed,backend network is good but still
>> we are not able to extract full capability of SSD disks.
>>
>>
>>
>> Thanks,
>
> Hi, i'm new to ceph so, don't consider my words as holy truth.
>
> It seems that Samsung 840 (so i assume 850) are crappy for ceph :
>
> MTBF :
> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2014-November/044258.html
> Bandwidth
> :http://lists.ceph.com/pipermail/ceph-users-ceph.com/2014-December/045247.html
>
> And according to a confirmed user of Ceph/ProxmoX, Samsung SSDs should
> be avoided if possible in ceph storage.
>
> Apart from that, it seems there was an limitation in ceph for the use
> of the complete bandwidth available in SSDs; but i think with less
> than 1Mb/s you haven't hit this limit.
>
> I remind you that i'm not a ceph-guru (far from that, indeed), so feel
> free to disagree; i'm on the way to improve my knowledge.
>
> Best regards.
>
>
>
>
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