On 10/27/2015 06:37 AM, Matteo Dacrema wrote:
Hi,
thanks for all the replies.
I've found the issue:
The Samsung nvme SSD has poor performance with sync=1. It reach only 4/5 k iops with randwrite ops.
Using Intel DC S3700 SSDs I'm able to saturate the CPU.
I'm using hammer v 0.94.5 on Ubuntu 14.04 and 3.19.0-31 kernel
What do you think about Intel 750 series : http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-750-series.html
I briefly considered 750s for some test boxes that wouldn't actually
hold real data, but even in that situation the write endurance is pretty
scary looking. I imagine they are probably going to do better than the
very low rating Intel give them (they sure look a lot like rebadged
P3500s), but in the end I ended up going with P3700s. The rated writ
endurance is just so much higher than it was worth the extra price (to
us at least).
I plan to use it for cache layer ( one for host - is it a problem? )
Behind the cache layer I plan to use Mechanical HDD with Journal on SSD drives.
What do you think about it?
Thanks
Regards,
Matteo
-----Original Message-----
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Somnath Roy
Sent: lunedì 26 ottobre 2015 17:45
To: Christian Balzer <chibi@xxxxxxx>; ceph-users@xxxxxxxxxxxxxx
Subject: Re: BAD nvme SSD performance
Another point,
As Christian mentioned, try to evaluate O_DIRECT|O_DSYNC performance of a SSD before choosing that for Ceph..
Try to run with direct=1 and sync =1 with fio to a raw ssd drive..
Thanks & Regards
Somnath
-----Original Message-----
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Somnath Roy
Sent: Monday, October 26, 2015 9:20 AM
To: Christian Balzer; ceph-users@xxxxxxxxxxxxxx
Subject: Re: BAD nvme SSD performance
One thing, *don't* trust iostat disk util% in case of SSDs..100% doesn't mean you are saturating SSDs there..I have seen a large performance delta even if iostat is reporting 100% disk util in both the cases.
Also, the ceph.conf file you are using is not optimal..Try to add these..
debug_lockdep = 0/0
debug_context = 0/0
debug_crush = 0/0
debug_buffer = 0/0
debug_timer = 0/0
debug_filer = 0/0
debug_objecter = 0/0
debug_rados = 0/0
debug_rbd = 0/0
debug_journaler = 0/0
debug_objectcatcher = 0/0
debug_client = 0/0
debug_osd = 0/0
debug_optracker = 0/0
debug_objclass = 0/0
debug_filestore = 0/0
debug_journal = 0/0
debug_ms = 0/0
debug_monc = 0/0
debug_tp = 0/0
debug_auth = 0/0
debug_finisher = 0/0
debug_heartbeatmap = 0/0
debug_perfcounter = 0/0
debug_asok = 0/0
debug_throttle = 0/0
debug_mon = 0/0
debug_paxos = 0/0
debug_rgw = 0/0
You didn't mention anything about your cpu, considering you have powerful cpu complex for SSDs tweak this to high number of shards..It also depends on number of OSDs per box..
osd_op_num_threads_per_shard
osd_op_num_shards
Don't need to change the following..
osd_disk_threads
osd_op_threads
Instead, try increasing..
filestore_op_threads
Use the following in the global section..
ms_dispatch_throttle_bytes = 0
throttler_perf_counter = false
Change the following..
filestore_max_sync_interval = 1 (or even lower, need to lower filestore_min_sync_interval as well)
I am assuming you are using hammer and newer..
Thanks & Regards
Somnath
Try increasing the following to very big numbers..
filestore_queue_max_ops = 2000
filestore_queue_max_bytes = 536870912
filestore_queue_committing_max_ops = 500
filestore_queue_committing_max_bytes = 268435456
Use the following..
osd_enable_op_tracker = false
-----Original Message-----
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Christian Balzer
Sent: Monday, October 26, 2015 8:23 AM
To: ceph-users@xxxxxxxxxxxxxx
Subject: Re: BAD nvme SSD performance
Hello,
On Mon, 26 Oct 2015 14:35:19 +0100 Wido den Hollander wrote:
On 26-10-15 14:29, Matteo Dacrema wrote:
Hi Nick,
I also tried to increase iodepth but nothing has changed.
With iostat I noticed that the disk is fully utilized and write per
seconds from iostat match fio output.
Ceph isn't fully optimized to get the maximum potential out of NVME
SSDs yet.
Indeed. Don't expect Ceph to be near raw SSD performance.
However he writes that per iostat the SSD is fully utilized.
Matteo, can you run run atop instead of iostat and confirm that:
a) utilization of the SSD is 100%.
b) CPU is not the bottleneck.
My guess would be these particular NVMe SSDs might just suffer from the same direct sync I/O deficiencies as other Samsung SSDs.
This feeling is re-affirmed by seeing Samsung listing them as a Client SSDs, not data center one.
http://www.samsung.com/semiconductor/products/flash-storage/client-ssd/MZHPV256HDGL?ia=831
Regards,
Christian
For example, NVM-E SSDs work best with very high queue depths and
parallel IOps.
Also, be aware that Ceph add multiple layers to the whole I/O
subsystem and that there will be a performance impact when Ceph is used in between.
Wido
Matteo
*From:*Nick Fisk [mailto:nick@xxxxxxxxxx]
*Sent:* lunedì 26 ottobre 2015 13:06
*To:* Matteo Dacrema <mdacrema@xxxxxxxx>; ceph-users@xxxxxxxx
*Subject:* RE: BAD nvme SSD performance
Hi Matteo,
Ceph introduces latency into the write path and so what you are
seeing is typical. If you increase the iodepth of the fio test you
should get higher results though, until you start maxing out your CPU.
Nick
*From:*ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] *On
Behalf Of *Matteo Dacrema
*Sent:* 26 October 2015 11:20
*To:* ceph-users@xxxxxxxx <mailto:ceph-users@xxxxxxxx>
*Subject:* BAD nvme SSD performance
Hi all,
I’ve recently buy two Samsung SM951 256GB nvme PCIe SSDs and built a
2 OSD ceph cluster with min_size = 1.
I’ve tested them with fio ad I obtained two very different results
with these two situations with fio.
This is the command : *fio --ioengine=libaio --direct=1 --name=test
--filename=test --bs=4k --size=100M --readwrite=randwrite
--numjobs=200 --group_reporting*
On the OSD host I’ve obtained this result:
*bw=575493KB/s, iops=143873*
* *
On the client host with a mounted volume I’ve obtained this result:
Fio executed on the client osd with a mounted volume:
*bw=9288.1KB/s, iops=2322*
* *
I’ve obtained this results with Journal and data on the same disk
and also with Journal on separate SSD.
* *
I’ve two OSD host with 64GB of RAM and 2x Intel Xeon E5-2620 @
2.00GHz and one MON host with 128GB of RAM and 2x Intel Xeon E5-2620
@ 2.00 GHz.
I’m using 10G mellanox NIC and Switch with jumbo frames.
I also did other test with this configuration ( see attached Excel
workbook )
Hardware configuration for each of the two OSD nodes:
3x 100GB Intel SSD DC S3700 with 3 * 30 GB
partition for every SSD
9x 1TB Seagate HDD
Results: about *12k* IOPS with 4k bs and same fio test.
I can’t understand where is the problem with nvme SSDs.
Anyone can help me?
Here the *ceph.conf:*
[global]
fsid = 3392a053-7b48-49d3-8fc9-50f245513cc7
mon_initial_members = mon1
mon_host = 192.168.1.3
auth_cluster_required = cephx
auth_service_required = cephx
auth_client_required = cephx
osd_pool_default_size = 2
mon_client_hung_interval = 1.0
mon_client_ping_interval = 5.0
public_network = 192.168.1.0/24
cluster_network = 192.168.1.0/24
mon_osd_full_ratio = .90
mon_osd_nearfull_ratio = .85
[mon]
mon_warn_on_legacy_crush_tunables = false
[mon.1]
host = mon1
mon_addr = 192.168.1.3:6789
[osd]
osd_journal_size = 30000
journal_dio = true
journal_aio = true
osd_op_threads = 24
osd_op_thread_timeout = 60
osd_disk_threads = 8
osd_recovery_threads = 2
osd_recovery_max_active = 1
osd_max_backfills = 2
osd_mkfs_type = xfs
osd_mkfs_options_xfs = "-f -i size=2048"
osd_mount_options_xfs = "rw,noatime,inode64,logbsize=256k,delaylog"
filestore_xattr_use_omap = false
filestore_max_inline_xattr_size = 512
filestore_max_sync_interval = 10
filestore_merge_threshold = 40
filestore_split_multiple = 8
filestore_flusher = false
filestore_queue_max_ops = 2000
filestore_queue_max_bytes = 536870912
filestore_queue_committing_max_ops = 500
filestore_queue_committing_max_bytes = 268435456
filestore_op_threads = 2
Best regards,
Matteo
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