How to force new folder on a certain drive?

[Carsten]

How can I create a new folder and force it immediatly to a certain drive? I tried to add the new folder in the drive pool (which got placed on a random disk) and then use the folder placement in "Balance" to force this new empty folder on this certain disk. But even after several hours nothing happend. I then tried rebalance, but unfortunately this also takes hours, because it starts the very expensive completely rebalance with all space balancing rules instead of first obeying the rules where to place a folder. And after a complete day, the folder is stil on the wrong disk.

 

One thing I need this for is when I add a new disk with data on it. Because copying 2-4 TB of data is really very slow and also a space problem, I want to create the DrivePool folder and then just move the data from out of the DrivePool directory on the same drive into the (hidden) DrivePool directory.

 

[Christopher (Drashna)]

I think you're looking for this:

http://wiki.covecube.com/StableBit_DrivePool_Q4142489

 

And to clarify a few things here:

• When you add a disk to the pool, it doesn't move the data into the pool by default. It's still on the disk.
  If you want it in the pool, you have to move it there yourself. We don't do this automatically, so that you can continue to use the disks however you want. Or more specifically, so we don't interfere with how you had your system setup.
• When placing files on the pool, they are placed on a "random" disk. Specifically, they're placed on the disk with the most available free space first. As the disks get filled and this space equalizes, then yes, it is much more randomly placed.
• If you're using StableBit DrivePool 2.X, you can use the "File Placement rules" to make sure a folder or files end up on a certain disk in the pool.
• You can use the "SSD Optimizer" balancer to speed up writes to the pool.
• Any files moved into the hidden "PoolPart" folders are immediately in the pool. However, they aren't properly "measured" until you remeasure the pool.

[Carsten]

As said, in the balancing I said, that a certain folder must only be on a certain drive, and also checked "Never allow files to be placed on other disks". But the folder is still not on the disk I want. I wanted to wait until this empty folder appears on the correct disk, where the data is already outside of the DrivePool directory, to be able to simply move the files on the same disk into the hidden DrivePool directory. So I would expect that hard file placement rules for a certain disk shoud be obeyed quickly, even before DrivePool starts balancing the drives for space distribution which is really just optimization not hard rules as the file placement rules (never allow files to be placed on other disks).

 

Two other questions:

Why is resetting neccessary, after moving files to the hidden pool directory? I did migrate lot's of files without resetting and without starting and stopping the service and it seems to work. Was this dangerous or to I risk inconsitencies?

 

How does DrivePool on which disk it finds a certain file? I suppose "Remeasing" builds up a database of where to find files. So after moving files to the hidden directories, DrivePool would needs a "Remeasuring".

[Christopher (Drashna)]

Which balancer are you using, specifically? 

Or is this the file placement rules? 

 

 

As for the resetting the settings after seeding the pool: 

To make sure StableBit DrivePool remeasures the pool, and can and so that it will apply the balancing settings. 

it's not strictly necessary, but you may run into balancing issues if you don't. At the very least, "remeasuring" the pool should correct that.

 

As for accessing the files, we do not maintain a database of the file locations. The "measurements" for the pool are mostly for the balancing engine.

As for the specifics, I'm going to quote Alex here:

When enumerating a folder, CoveFS will query every single pool part that's part of the pool for its contents. This may wake all the drives up if the NTFS file system metadata for that folder is not in the cache and needs be read in.

 

When reading or writing to a specific file, or querying information about a specific file then only the drives that that file is on are accessed.

 

So in short, for directory enumerations all drives are accessed and for file access, only the specific drives that the file is on are queried.

[Markus]

As this relates to the original question: I followed the whs migration guide, but the folders I am supposed to move to do not exist yet in most of the drivepool directories (only on one or two drives). Am I safe to assume that just creating the neede folders (e.g. "ServerFolders/Users/Markus) and then moving stuff from the DE shares into the newly created folders is ok/safe?

[Christopher (Drashna)]

You've asked this in a ticket already, but I'll answer here as well.

 

Yes, you'd want to create the folder before moving files around.

 

THis is mentioned as step #5 in the migration instructions, but I'll make it clearer.