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Very low SMB write performance compared to direct CephFS access


Vishnu Bhaskar
22 Posts
November 21, 2025, 11:52 am

I have a PetaSAN setup where I am trying to connect an SMB share to Windows. While benchmarking the SMB share, I am unable to achieve performance close to what I get when writing directly to CephFS.

I performed three tests using 1 MiB sequential write:

  1. Direct CephFS write: ~ 1000 MiB/s

  2. SMB write from Ubuntu client: ~ 60 MiB/s

  3. SMB write from Windows client: ~ 20 MiB/s

The write performance through SMB is significantly lower than direct CephFS access. I would like support in identifying the cause and improving SMB write performance.

#1

admin
3,054 Posts
November 21, 2025, 12:51 pm
  1. Can you describe in summary your hardware setup, ram, cpu, disk ( SSD or HDD )
  2. When you write directly to CephFS, what command do you use ? what is block size used in writes ? are you using buffered i/o or using direct/sync i/o ?
  3. Similarly can you describe the commands used in Windows and Linux writing to SMB?

 

#2