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Will Mover start when cache drive is full?


jgourd

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no, the cache drive will fill up, and then it will bypass the cache writing directly to the array.

 

if you are planning on copying 6TB at once, i would disable the cache until you are done.

 

what will probably happen is you will fill the cache and then bypass it once filled. sometime around 4:30am, the mover script will kick off and it will also start writing to the array while your 6tb is still going.

I would then guess you will then bring array to a crawl as you overload the parity drive if you have all LP drives. I would also assume You would also get fragmentation when that happens?

 

in the end, it would be better to bypass the cache for file transfers that exceed the cache drive in my opinion.

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  • 2 years later...

Is it true that it bypasses the cache drive? I get disk full errors all over the place. :(

Is there a way to auto start the mover when the min free space is reached? I mean... after all I thought this is the sense of this setting?

 

Raise the min free space setting. If the file is larger than both the min free space setting and the amount of free space, it can fill the cache and then cause a disk full error. Once the cache has exceeded the min free space allocation the next file written will go directly to the cache. Once unRAID selects a disk the entire file must fit on the destination drive. It is safest if the min free space setting is twice the size of the largest file you anticipate writing.

 

Mine is set to 50GB. The disks can be topped off manually when desired.

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Is it true that it bypasses the cache drive? I get disk full errors all over the place. :(

Is there a way to auto start the mover when the min free space is reached? I mean... after all I thought this is the sense of this setting?

I see this behavior as well.

In particular, if I have multiple copy operations running, each of which would individually fit, but which together fill the cache drive, there's a messy result.

The cure is simple..no multiple copy operations!  (a copy of multiple files is fine...but multiple simultaneous copies won't correctly calculate the amount of remaining free space) 

 

If I was moving a full Drobo, I'd turn off cache drive completely...in fact:


Alternate suggestion:

A little 'risky', but if you're migrating from Drobo, and Drobo is a complete backup, and you don't have any files on your unRAID currently, you might consider turning off the parity drive and the cache drive...fire up unRAID without parity protection...copy all your files (at full speed, YAY!) and then when your copy is finished, turn on Parity.  It will take a long time to create and write Parity, but I suspect it would be faster overall...  Get a second opinion on this idea...and consider the risks associated.

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When a file is opened for writing the server has no idea of the final file size. This is true for file copies as well. So even a single file wire can cause a disk full issue if the server is not configured correctly.

 

Disabling the parity drive only makes sense if your using Teracopy or something like it to verify the file writes. There are 4 options:

 

1. no parity, no verify: bad idea

2. parity, no verify: safe

3. no parity, verify: safe (slightly safer)

4. parity, verify: safest (but is overkill)

 

The option are ordered from fastest to slowest. You should pick option 2 or 3.

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