Cache speed (disk share vs user share)


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Hey everyone,

 

I recently rebuilt my unraid server and I'm seeing some strange cache write speed behavior.  If I write to a user share that has use cache set to Yes via SMB I can copy at about 280 MB/s which is slow.  If I enable disk shares and do the same copy direct to the cache drive share I get well over 1 GB/s which is what I'd expect.  The only thing I've tried so far is enabling Direct IO but that didn't help.

 

The cache drive is a hardware raid of SAS3 SSDs.  The PC I'm copying from has a PCIE 4.0 nvme disk in it.   Diagnostics attached.  Any help would be appreciated!

 

Thanks

 

 

tower-diagnostics-20200309-1707.zip

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  • 1 month later...
On 3/9/2020 at 9:16 PM, testdasi said:

...

 

What I have been doing is to have custom smb config that targets /mnt/cache directly (instead of enabling disk shares) to get max performance.

Hey, any chance you can do this "custom smb config that targets /mnt/cache directly" thingy?

Thanks

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27 minutes ago, SpeedyVV said:

Hey, any chance you can do this "custom smb config that targets /mnt/cache directly" thingy?

Thanks

 

Below is what works for me.  I usually just write 1 file through the user share and then once the folder structure is created I do the rest of my writes through the cache share. Its clunky, but it works for now until I can think of a more elegant solution.

 

[cacheShare]
  path=/mnt/cache
    valid users = whoever
    write list = whoever

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If you stop your array, go into settings, then click on SMB there is a section called "Samba extra configuration:"  That's where you paste the config I shared.  After you start the array you should now see an extra share when you browse to your server.  You don't need to create it under the "Shares" area of unraid.  I would turn off disk shares unless you need it for something specific.  

  • Thanks 1
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2 hours ago, bonienl said:

For all disk shares set Export=No,

except for cache set Export=Yes

 

I was referring to my hack of copying a single file via user shares to create directory structures and then copying the rest of the files via the cache share because of transfer speed being comparatively slow through user shares when writing to cache. 

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