Author Topic: Reserve not working?  (Read 1798 times)

Offline alaneisen

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Reserve not working?
« on: April 18, 2012, 02:06:30 pm »
I am a new user to Flexraid.  I setup a CC Snapshot Raid with 6 DRUs (all 4TB drives) and 2 PPUs (also 4 TB drives) on WHS 2011.  With the larger drive size, I want a larger reserve space before the drive is full.  I've changed the Reserve setting under Run-Time Properties-->Advanced Properties to 100GB.

But when I'm testing it, the first drive continues to get files even with less than 100Gb on it.  No other drive has any data on them.  (New setup.)  I've restart the box already. 

I'm on 2.0u4 right now. 

Thanks, Alan

Offline alaneisen

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Re: Reserve not working?
« Reply #1 on: April 22, 2012, 09:18:12 am »
Bump?  Anyone with any input?  Is there a benefit for keeping a larger reserve other than getting rid of the "low disk space" warning in WHS2011?

Offline maschibd

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Re: Reserve not working?
« Reply #2 on: April 30, 2012, 08:23:37 am »
The reserve helps to prevent "insufficient space" warnings.  For instance, if the reserve is set for 10 GB (default), and you try to copy a 12 GB file onto the array, it could fail with an "insufficient space" error.  So the reserve should be set to allow for the largest file to be copied...

Offline Mondo

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Re: Reserve not working?
« Reply #3 on: April 30, 2012, 10:27:15 am »
The reserve helps to prevent "insufficient space" warnings.  For instance, if the reserve is set for 10 GB (default), and you try to copy a 12 GB file onto the array, it could fail with an "insufficient space" error.  So the reserve should be set to allow for the largest file to be copied...

This is correct..

I've changed the Reserve setting under Run-Time Properties-->Advanced Properties to 100GB.

But when I'm testing it, the first drive continues to get files even with less than 100Gb on it.  No other drive has any data on them.  (New setup.)  I've restart the box already. 

I *think* it works on these conditions:

If you have less than 100GB left when you start a copy operation the storage pool driver will switch to the next drive with sufficient space.

If you have more than 100GB left when you start the copy operation and the file/s being copied is less than 100GB it will copy even though you are going below your reserve space. So theoretically you could copy a 99GB file and get left with less than 2GB of free space if the right conditions are met.

If you have 100GB left and you try and copy a 120GB file this would generate an error. FlexRAID attempts to move the data to the next drive when it reaches capacity but I think most copy operations would time out long before that.

Brahim may well shoot some of this down as I'm only going from observation...


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Offline Brahim

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Re: Reserve not working?
« Reply #4 on: April 30, 2012, 10:39:45 am »
...
If you have less than 100GB left when you start a copy operation the storage pool driver will switch to the next drive with sufficient space.

If you have more than 100GB left when you start the copy operation and the file/s being copied is less than 100GB it will copy even though you are going below your reserve space. So theoretically you could copy a 99GB file and get left with less than 2GB of free space if the right conditions are met.

If you have 100GB left and you try and copy a 120GB file this would generate an error. FlexRAID attempts to move the data to the next drive when it reaches capacity but I think most copy operations would time out long before that.

Brahim may well shoot some of this down as I'm only going from observation...
Correct with one rectification.
If you have 100GB left and try to copy 120GB:
- if the copy process pre-allocates or probes for the size ahead of time (as it is typical with file copies), FlexRAID will move the file to the next available drive with sufficient space
- otherwise, if FlexRAID has no way of knowing what the final size will be, then the copy will start on the first drive and move to the next if it runs out space. As noticed, the move process can timeout depending on the program. FlexRAID tries to extend the timeout automatically, but different program behave differently. For instance, a live TV show recording will have issues being suspended for 5 minutes while the move is happening and its buffer runs out.

Offline alaneisen

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Re: Reserve not working?
« Reply #5 on: May 03, 2012, 06:46:25 am »
Thanks all.  It's funny, I had to recreate my array (added a PPU) and now the next drive the reserve worked fine.  I now am not getting the stupid low disk space from WHS 2011.