unRAID

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SamHill Offline
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Location: Lacey, WA.
Post: #1
I have a quick question for all you unRAID users out there.

Are you able to create unRAID with drive that have data on them already, or do you need to create the unRAID with empty drives.?.Confused

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Choque Offline
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Location: Bavaria, Germany
Post: #2
You have to preclear a drive (overwriting every sector of the drive with zeros) and format it after that before you can assign the drive as a data drive in unRAID.

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(This post was last modified: 2011-05-13 08:43 by Choque.)
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SamHill Offline
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Location: Lacey, WA.
Post: #3
Choque Wrote:You have to clear or preclear a drive (overwriting every sector of the drive with zeros) and format it after that before you can assign the drive as a data drive in unRAID.

Thanks you for the explanation. When you set it up is it through a GUI or text based?

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Choque Offline
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Post: #4
You can either preclear the drives through unRAIDs web interface but your array will be offline for the whole time (clearing a 2TB drive takes 25h+ and it's advised to clear a new drive 3x to be sure it's not defective). So that would render your server unusable for around 75 hours +/-
The other way (which I would recommend to you) is preclearing the drives through the preclear_disk.sh script. You'd have to do that through a telnet session as explained here. The big advantage of this method is that you can preclear a drive during the array is running so you would not have to suffer under a huge downtime.

If you want to get an overview of how to get started with unRAID and the configuration, I'd recommend reading this tutorial.

I haven't had a clue about unRAID and got it working just following the steps in this tutorial. It's really easy Smile

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(This post was last modified: 2011-05-13 08:45 by Choque.)
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smiffy1989 Offline
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Post: #5
I think your in a similar situation to what I was when I was building my unraid box. Already had 2x2TB drives that were almost full of data that I wanted to keep.

What I did was bought 2 new 2TB drives and put them into my unraid box along with the 2x2TB drives I had already. I assigned the new drives to the array but just mounted the old drives and copied all the data from them to the new drives that were part of the array. Once I had all the data I cleared the old drives and assigned them both to my array.

There's a guide on the unraid forums for doing that. I'd link you but it's a farce on the iPhone :/ If you google 'move files within unraid' it should come straight up.

The link that Choque posted is what I used to setup my server too Smile
(This post was last modified: 2011-05-13 08:54 by smiffy1989.)
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wsume99 Offline
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Post: #6
Choque Wrote:You can either preclear the drives through unRAIDs web interface but your array will be offline for the whole time (clearing a 2TB drive takes 25h+ and it's advised to clear a new drive 3x to be sure it's not defective). So that would render your server unusable for around 75 hours +/-
The other way (which I would recommend to you) is preclearing the drives through the preclear_disk.sh script. You'd have to do that through a telnet session as explained here. The big advantage of this method is that you can preclear a drive during the array is running so you would not have to suffer under a huge downtime.
Sorry but I have to correct what you said here because it is not entirely accurate. First and foremost preclearing a drive (as you speak of it) is NOT an unRAID function but instead it is a user developed script. When you add a drive to the unRAID array the sever has to format the drive first before it can be used. During this time it will do several things like creating the MBR and then writing a zero to all blocks on the disk for example. During the formatting process the array will be unavailable (i.e. you can't read or write to/from it). Additionally this is a one time event and there is nothing done to check the integrity of the disk you are adding. Now a very intelligent user (Joe L.) has written a script called preclear_disk that will accomplish essentially the same things that unRAID does but also exercises the disk to uncover problems as well. The preclear process has essentially three phases. First it reads every block on the entire disk, this is what's know as the pre-read. Then it creates the MBR and writes zeroes on the disk just as unraid would do. The last step is reading the entire disk again to confirm that zeros have indeed been written to every block, this is what's know as the post-read. The purpose of the pre and post-read is to simply exercise the disk and uncover any problems that show up as a result of exercising all the blocks on the disk. The problems will show up in the SMART reports as a result of these activities in the form of reallocated sector counts, read errors, pending sector counts, etc. It is possible to run a preclear and skip the pre and post-read steps and just do the zeroing. For a 2TB disk the entire three phase process would take about 22-30 hours depending on the speed of the disk. The first and second phases usually each take about 1/4 of the total time and remaining half is spent on the third phase. This all can be done while the array is completely functional. Plus you can preclear multiple disks at the same time. The most I've seen is six at a time. I've personally done three different disks at the same time. I run all my new disks through the complete preclear process three times before I ever add them to my array. This gives me confidence that I have a good disk before adding it to my array. When you stop the array to add a new disk that has been precleared using this script unRAID recognizes the disk as already being formatted and the time it takes to add it to the array is just a few minutes.

Choque Wrote:I haven't had a clue about unRAID and got it working just following the steps in this tutorial. It's really easy Smile
I too was clueless but that didn't prevent me from getting everything up and running in no time. Basically you just need to be able to read English.

HTPC: Win 7 Home 64-bit | MB | CPU | GPU | RAM | Case | PSU | Tuner | HDDs: OS, Media | DVD Burner | Remote
Media server: unraid 4.7 | CPU | MB | RAM | Case | PSU | HDDs: Parity-2TB, Data-2x2TB
(This post was last modified: 2011-05-13 19:40 by wsume99.)
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Choque Offline
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Post: #7
Actually you have to correct yourself.
Quote:When you stop the array to add a new disk that has been precleared using this script unRAID recognizes the disk as already being formatted and the time it takes to add it to the array is just a few minutes.
unRAID detects the disk as already PRECLEARED and you then can simply format the disk which takes roughly 2 minutes (during which the array will be offline) and you can then add it to the array.

And I never said preclearing is an unRAID function, hence I mention "preclear_disk.sh" which should make it obvious that it's a script.
And it doesn't really matter if the process is called preclearing or not if you do it within unRAID and not with the script. The fact remains that your array will be offline for the time it performs the "whatever-it's-called" and that during this process the drive will be filled with zeros on each sector.

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smiffy1989 Offline
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Post: #8
I like to live life on the wild side and so didn't bother preclearing Big Grin
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wsume99 Offline
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Post: #9
Choque Wrote:And I never said preclearing is an unRAID function
Really? Then why did you say this ...
Choque Wrote:You can either preclear the drives through unRAIDs web interface ...
Th only things you'll find in the unRAID web interface are unRAID functions. There is no way to preclear a drive in the unRAID web interface because it's not an unRAID function. All you can do is assign a new drive to the array. My point is that when you say "preclear" to most (if not all) users in the unRAID community that has a very specific meaning and it is reference to the preclear_disk script, not the process by which unRAID adds a new disk. These are two different things in my opinion.

I am not criticizing you specifically but just responding to a statement that I thought was not accurate and might confuse potential unRAID users.

HTPC: Win 7 Home 64-bit | MB | CPU | GPU | RAM | Case | PSU | Tuner | HDDs: OS, Media | DVD Burner | Remote
Media server: unraid 4.7 | CPU | MB | RAM | Case | PSU | HDDs: Parity-2TB, Data-2x2TB
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Choque Offline
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Posts: 233
Joined: Apr 2011
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Location: Bavaria, Germany
Post: #10
Yea well, the fact remains that unRAID does the "zero to all sectors thingy" too and I refer to this as preclearing. Wasn't my intention to sound harsh btw Smile

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