Re: Small-cluster performance issues

[fcid <fcid@xxxxxxxxxxx>]

Hi David

I'll try to perform these tests soon.

Thank you.

On 08/22/2017 04:52 PM, David Turner wrote:

I would run some benchmarking throughout the cluster environment to see where your bottlenecks are before putting time and money into something that might not be your limiting resource.  Sebastian Han put together a great guide for benchmarking your cluster here.

https://www.sebastien-han.fr/blog/2012/08/26/ceph-benchmarks/

Test to see if it's your client configuration, client's connection to the cluster, the Cluster's disks, the cluster overall speed, etc.

On Tue, Aug 22, 2017 at 3:31 PM Mazzystr <mazzystr@xxxxxxxxx> wrote:

Also examine your network layout.  Any saturation in the private cluster network or client facing network will be felt in clients / libvirt / virtual machines

As OSD count increases...

• Ensure client network private cluster network seperation - different nics, different wires, different switches
• Add more nics both client side and private cluster network side and lag them.
• If/When your dept's budget suddenly swells...implement 10 gig-e.

Monitor, capacity plan, execute  :)

/Chris C

On Tue, Aug 22, 2017 at 3:02 PM, Maged Mokhtar <mmokhtar@xxxxxxxxxxx> wrote:

 

It is likely your 2 spinning disks cannot keep up with the load. Things are likely to improve if you double your OSDs hooking them up to your existing SSD journal. Technically it would be nice to run a load/performance tool (either atop/collectl/sysstat) and measure how busy your resources are, but it is most likely your 2 spinning disks will show near 100% busy utilization.

filestore_max_sync_interval: i do not recommend decreasing this to 0.1, i would keep it at 5 sec 

osd_op_threads do not increase this unless you have enough cores.

but adding disks is the way to go

Maged

 

On 2017-08-22 20:08, fcid wrote:

Hello everyone,

I've been using ceph to provide storage using RBD for 60 KVM virtual machines running on proxmox.

The ceph cluster we have is very small (2 OSDs + 1 mon per node, and a total of 3 nodes) and we are having some performace issues, like big latency times (apply lat:~0.5 s; commit lat: 0.001 s), which get worse by the weekly deep-scrubs.

I wonder if doubling the numbers of OSDs would improve latency times, or if there is any other configuration tweak recommended for such small cluster. Also, I'm looking forward to read any experience of other users using a similiar configuration.

Some technical info:

  - Ceph version: 10.2.5

  - OSDs have SSD journal (one SSD disk per 2 OSDs) and have a spindle for backend disk.

  - Using CFQ disk queue scheduler

  - OSD configuration excerpt:

osd_recovery_max_active = 1
osd_recovery_op_priority = 63
osd_client_op_priority = 1
osd_mkfs_options = -f -i size=2048 -n size=64k
osd_mount_options_xfs = inode64,noatime,logbsize=256k
osd_journal_size = 20480
osd_op_threads = 12
osd_disk_threads = 1
osd_disk_thread_ioprio_class = idle
osd_disk_thread_ioprio_priority = 7
osd_scrub_begin_hour = 3
osd_scrub_end_hour = 8
osd_scrub_during_recovery = false
filestore_merge_threshold = 40
filestore_split_multiple = 8
filestore_xattr_use_omap = true
filestore_queue_max_ops = 2500
filestore_min_sync_interval = 0.01
filestore_max_sync_interval = 0.1
filestore_journal_writeahead = true

Best regards,

 

 

_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com

-- 
Fernando Cid O.
Ingeniero de Operaciones
AltaVoz S.A.

_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com