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Adding recovered drive by Snapraid again to the pool


PaulDek

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Hi all,

For my server I have been investigating several storage solutions. My latest test was with DrivePool (and Scanner/CloudDrive) combined with Snapraid. I was inspired by this video:

DrivePool + Snapraidyoutube.com/watch?v=kDCMpVgZb4g

Tested that on a test setup and it is easy as 1 2 3.

When I deleted a volume and created a new one to simulate a drive failure to test Snapraid recovery I removed the "failed" hard drive from my pool, did the recovery with Snapraid (which worked like a charm). Then added the drive back to my pool: but what DrivePool then does is creating a new hidden drivepool folder with a new guid, also the old data is then not visible. If I then by hand move all the data from the old DrivePool guid folder to the new one it becomes visible again.

Not a very big issue, but I wondered if I did something wrong, or this is normal behavior of DrivePool. I would think it would have recognized the existing DrivePool folder and use that guid so all data is back again without moving files manually.

Any ideas about this?

Also when doing some more testing I changed in one occasion the drive letter of the newly created volume: the new drive letter did not become visible in Snapraid, also not after a PC reboot. Then I read that sometimes this occurred and that resetting all settings should help, and yes that did bring up the drive.

I was really doubting if I should go for only DrivePool duplication or DrivePool without duplication and using Snapraid for parity. After a lot of reading and trying myself I now am convinced I should go for the DrivePool + Snapraid config: a litte bit more setup to do (mainly scheduling a script, but there is a nice one to start with from codeplex), but I do get protection against bitrot, and for my five 4TB drives I will get 16GB of protected storage (against one disk failure at a time).

Anyone has some arguments to talk me out of this and only use DrivePool with duplication? For me the main win for that would be simplicity, but at the expense of space (not my number one problem), but also no protection against bitrot.

Thanks!

Best regards,
Paul

 

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I definitely suggest configuring snapraid so it points to the drivepool folder with the GUID inside the config file so that it's much easier to restore. Snapraid doesn't have to be the root of the drive, it can be anywhere you like (as long as they are on different psychical drives).

So instead of doing:

data d1 z:\
data d2 y:\
data d3 x:\

You do:

data d1 z:\drivepool.{guid}\
data d2 y:\drivepool.{guid}\
data d3 x:\drivepool.{guid}\

That way after a failure e.g d2 dies, you drop your new drive in, add it to the pool, get the new GUID from the new drive, and edit your snapraid conf to comment out the old drive and add the new one by changing d2 y:\drivepool.{guid}\ to d2 y:\drivepool.{newguid}\ like so:

data d1 z:\drivepool.{guid}\
#data d2 y:\drivepool.{guid}\
data d2 y:\drivepool.{newguid}\
data d3 x:\drivepool.{guid}\

Then run your fix and it all just works - and you don't have to move your files around. 

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On 5/10/2019 at 1:22 PM, PaulDek said:

Not a very big issue, but I wondered if I did something wrong, or this is normal behavior of DrivePool. I would think it would have recognized the existing DrivePool folder and use that guid so all data is back again without moving files manually.

Yeah, that would be normal.  When adding the disk to the pool, it creates a random ID, and that ID is part of the "PoolPart" folder's name. 

So, it will cause this. 

And i think that SnapRAID does not back up the Alternate Data Streams that StableBit DrivePool uses, hence the issue.   I'm not sure if there is a way to fix that, really. 

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Ok, I understand. But why does DrivePool not check if the added disk has already a PoolPart (with random ID) folder: and if so: show a dialog box that an existing pool part was found on the disk and if you would like to add that one, or create a new one.

And in this case DrivePool could even have recognized the pool part having the exact same ID as the previous lost disk (as Snapraid brings that back on the new disk)...and then could give a dialog box that the new drive has the same pool part as the lost disk and if you want to add it back again.

Am I missing something (the Alternate Data Streams?), or could you explain why this is not possible?

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On 6/12/2019 at 2:41 PM, Christopher (Drashna) said:

Well, if you use the "dpcmd" utility, there is actually an option to do that. 

As for the UI, I think the reason that it doesn't, is mostly to keep it simple, and not overly complex/cluttered. 

Im having the same issue. Attempting to rename a drivepool guid to a previous guid. Can you please provide a link to the commands for this? I cant find much documentation for the dpcmd utility, Im sure its right under my nose.

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There isn't any documentation for it (other than snippets posted in the forums), because the dpcmd utility is not meant for normal usage and bypasses a number of normal checks and procedures. 

However, the utility itself will give a basic description.  But in this case, "dpcmd unignore-poolpart poolpart.xxxxx x:" is what you want. 

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