topic Re: Weird read / write performance of XFS on NetApp LUN in ONTAP Discussions

Weird read / write performance of XFS on NetApp LUN

PhilDai1 — Wed, 31 Jul 2024 05:06:06 GMT

Hi all,

IHAC met a weird performance issue with XFS:

Mapped a LUN from a FAS8300 (ONTAP 9.7) to a CentOS 7.8 system
Aggregate consist of 56 NL-SAS disks
tested the throughput of LUN ( on RAW device), both read and write throughput > 500MB/s
Formated that LUN and create a XFS file system and used FIO to test the throughput of file system
- Write throughput > 500MB/s
- Read throughput < 100MB/s -- weird

Any thoughts and suggestions? Thanks in advance!

Best Regards,

Phil

TMACMD — Wed, 31 Jul 2024 11:32:13 GMT

I’ll start. How is the lun attached?

Iscsi, fc, nvme/tcp or nvme/fc?

How many lifs per node?

PhilDai1 — Thu, 01 Aug 2024 02:30:06 GMT

Hi TMACMD,

Thanks for your respond!

It is FC protocol. 2 lifs per node.

Thanks!

-Phil

TMACMD — Thu, 01 Aug 2024 10:11:32 GMT

And what was the FIO command/args used for testing?

Did you try formatting the lun with other formats and test besides XFS?

It could be some kind of caching issue

PhilDai1 — Fri, 02 Aug 2024 13:41:16 GMT

Hi TMACMD,

Command was like:

fio -directory=/test02 -direct=1 -rw=write -bs=128k -size=15G -numjobs=16 -runtime=300 -group_reporting -name=test-write

Single LUN on a volume, was mapped to the Linux Server.

On the Linux Server, they did not create partition or use LVM.

We will try:

1. create a partition before makes

2. try ext4 file system for comparision

Thanks!

-Phil

PhilDai1 — Fri, 09 Aug 2024 13:15:32 GMT

Customer has done tests today:

Please find results as below (block size 128K):

No big difference between XFS and Ext4
It is interesting that read throughput (on XFS) increased to 139MB/s when customer did the read test 2nd time, compared to 75MB/s at the 1st time
In contrast, read throughput was close to write when customer did the same test on SSD LUN

Any thoughts?