Slow ceph journal on Samsung 850 Pro

[carlosmp]

Seeing something very odd with Samsung 850 Pro SSD as Ceph journal. When running tests for speed as per:
https://www.sebastien-han.fr/blog/2...-if-your-ssd-is-suitable-as-a-journal-device/ I'm getting extremely low numbers.:

1 - io=83448KB, bw=1390.8KB/s, iops=347, runt= 60001msec
5 - io=243020KB, bw=4050.3KB/s, iops=1012, runt= 60001msec
10 - io=405004KB, bw=6749.6KB/s, iops=1687, runt= 60005msec

On other drives I get:

ATA device, with non-removable media
Model Number: INTEL SSDSC2CW060A3
Firmware Revision: 400i

1 - io=549996KB, bw=9166.5KB/s, iops=2291, runt= 60001msec
5 - io=1307.5MB, bw=22314KB/s, iops=5578, runt= 60001msec
10 - io=2352.5MB, bw=40148KB/s, iops=10037, runt= 60001msec

ATA device, with non-removable media
Model Number: KINGSTON SV300S37A60G
Firmware Revision: 505ABBF0

1 - io=552004KB, bw=9199.1KB/s, iops=2299, runt= 60001msec
5 - io=1273.1MB, bw=21742KB/s, iops=5435, runt= 60001msec
10 - io=2287.3MB, bw=39035KB/s, iops=9758, runt= 60001msec

ATA device, with non-removable media
Model Number: SanDisk SDSSDHII120G
Firmware Revision: X31200RL

1 - io=456000KB, bw=7599.9KB/s, iops=1899, runt= 60001msec
5 - io=1683.5MB, bw=28730KB/s, iops=7182, runt= 60001msec
10 - io=2349.8MB, bw=40090KB/s, iops=10022, runt= 60001msec

ATA device, with non-removable media
Model Number: Samsung SSD 850 PRO 256GB
Firmware Revision: EXM02B6Q

1 - io=89164KB, bw=1485.2KB/s, iops=371, runt= 60003msec
5 - io=386468KB, bw=6441.3KB/s, iops=1610, runt= 60001msec
10 - io=509944KB, bw=8498.9KB/s, iops=2124, runt= 60002msec

ATA device, with non-removable media
Model Number: Samsung SSD 850 EVO 250GB
Firmware Revision: EMT02B6Q

1 - io=322772KB, bw=5379.5KB/s, iops=1344, runt= 60001msec
5 - io=1182.8MB, bw=20185KB/s, iops=5046, runt= 60001msec
10 - io=1853.5MB, bw=31631KB/s, iops=7907, runt= 60002msec

ATA device, with non-removable media
Model Number: SanDisk SDSSDHP256G
Serial Number: 134731400200
Firmware Revision: X2306RL

1 - io=362044KB, bw=6033.1KB/s, iops=1508, runt= 60001msec
5 - io=1166.8MB, bw=19911KB/s, iops=4977, runt= 60001msec
10 - io=1952.4MB, bw=33319KB/s, iops=8329, runt= 60002msec

These are all on the same box (Dell C2100, 96GB RAM, 2xX5650, ICH10).

The more I dig around, the more I see folks avoiding Samsung drives on ceph. Perhaps the wiki should reflect not to use Samsung Pro...http://pve.proxmox.com/wiki/Ceph_Server

 

[dcsapak]

in the link you posted it states explicitly:

Consumer SSD MODEL Firmware 1 JOB 5 JOBS 10 JOBS
...
Samsung 850 Pro 256GB ??? 1.5 MB/s ??? MB/s ??? MB/s
Samsung 850 Pro 128GB ??? 1.2 MB/s ??? MB/s ??? MB/s

so your 1.3 MB/s are in line with the data there.

The problem is, that the Samsung PRO are really "prosumer" devices and not suited for
data center usage.

but yes, i will put the link of the blog in the wiki

 

[carlosmp]

Yes, I was quite shocked when i came across the results. I was expecting things to be fairly even across most of the drives. The real difference I thought was in the TBW/DWPD. Barring the NVMe and high end enterprise SAS, which are definitely in a different ball park. We just received a Kingston KC400 and results are (better than the Pro 850, but still sub-par, using the dated Intel 520 as a middle of the road...

ATA device, with non-removable media
Model Number: KINGSTON SKC400S37256G
Firmware Revision: SAFM00.W

1 - io=118688KB, bw=1978.2KB/s, iops=494, runt= 60001msec
5 - io=583592KB, bw=9726.3KB/s, iops=2431, runt= 60002msec
10 - io=1051.5MB, bw=17944KB/s, iops=4485, runt= 60003msec

 

[carlosmp]

I would suggest the Smsung SM863, as the cost is very similar to Samsung Pro 850, but performance is pretty high up there. This is connected to an ICH10 so 3GB port...

ATA device, with non-removable media
Model Number: SAMSUNG MZ7KM240HAGR-0E005
Firmware Revision: GXM1003Q

1 - io=1676.9MB, bw=28617KB/s, iops=7154, runt= 60001msec
5 - io=2122.1MB, bw=36231KB/s, iops=9057, runt= 60001msec
10 - io=2618.4MB, bw=44684KB/s, iops=11171, runt= 60002msec