ZFS Mirrored NVMe + Debian / LXC - Slower than expected

Patrick

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I was running some sysbench OLTP tests on a dual E5-2699 V3 server. I saw some extremely strange results. These drives were coping images via DD about 3x as fast as the S3700 + SanDisk LB406s (400GB SLC) drives ZFS mirrors in the Las Vegas colo.

Setup:
  • Proxmox VE 4.0 (Debian Jessie)
  • SSDs set as ZoL mirrored SSD pairs
  • Stock drivers
  • Dual Intel Xeon E5-2699 V3 server
  • LXC containers with Ubuntu 14.04 using the ZFS mirrored pairs of drives as storage 8 cores dedicated
  • Sysbench OLTP tests against MySQL 5.6
  • Containers were run using the exact same test setups
The drives used were:
  • 2x Intel DC S3710 200GB
  • 2x Intel DC P3600 400GB
  • 2x Samsung XS1715 800GB
Here is what I saw:
upload_2015-11-21_21-14-47.png
Seems like there is something going on with the NVMe drives.
 

Patrick

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Well, trying it on the ceph storage now just to see what happens.
 

Patrick

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And now we enter the completely bizzare sysbench result:
upload_2015-11-22_17-13-40.png

Ceph had one request I saw in the 195ms range too!
 

Jeggs101

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Dec 29, 2010
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I'd like to know what you're running to get that. Maybe we can all pitch in a VM's worth of data or two?
 

Patrick

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I'd like to know what you're running to get that. Maybe we can all pitch in a VM's worth of data or two?
Might be worth a shot. But just as a sanity check I tested a Samsung XS1715 alone using:
Code:
hdparm -tT --direct /dev/nvme0n1
and got:
Code:
root@fmt-pve-01:/home/test# hdparm -tT --direct /dev/nvme0n1

/dev/nvme0n1:

 Timing O_DIRECT cached reads:   5204 MB in  2.00 seconds = 2602.12 MB/sec
 Timing O_DIRECT disk reads: 6718 MB in  3.00 seconds = 2239.10 MB/sec
and also the Intel DC P3600:

Code:
# hdparm -tT --direct /dev/nvme2n1

/dev/nvme2n1:
 Timing O_DIRECT cached reads:   3256 MB in  2.00 seconds = 1628.05 MB/sec
 Timing O_DIRECT disk reads: 4604 MB in  3.00 seconds = 1534.54 MB/sec
Here is a SAS2 Samsung SM1625 200GB:
Code:
# hdparm -tT --direct /dev/sdf

/dev/sdf:
 Timing O_DIRECT cached reads:   1032 MB in  2.00 seconds = 515.12 MB/sec
 Timing O_DIRECT disk reads: 1346 MB in  3.00 seconds = 448.37 MB/sec
And a SATA III Intel S3710 200GB:
Code:
# hdparm -tT --direct /dev/sdb

/dev/sdb:
 Timing O_DIRECT cached reads:   850 MB in  2.00 seconds = 424.21 MB/sec
 Timing O_DIRECT disk reads: 1426 MB in  3.00 seconds = 475.01 MB/sec
Raw read speeds seem to favor the NVMe drives clearly. If it were the ZFS mirror, I would expect the S3710's to experience similarly poor results if not worse due to the underlying hardware.