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Do you preclear only new drives?


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Do I need to preclear every single drive coming into UnRaid? I mean I know you preclear the new ones you buy, but what about ones that are coming from a Windows build? I'm asking cause I have a 2 TB WDigital in a windows server I'd like to transfer over. Also, being that I have a new build, I haven't assigned an array just yet but I have precleared all the drives and shut the pc down. I'm expecting another shipment of drives in the mail next week and wanted to just get all the preclearing out of the way before I started transferring data. Not sure if what I said made sense I'm working on 3 hours of sleep and my brain is fried but figured if I didn't ask this now I'd definitely forget.

 

I appreciate any help.

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Do I need to preclear every single drive coming into UnRaid? I mean I know you preclear the new ones you buy, but what about ones that are coming from a Windows build? I'm asking cause I have a 2 TB WDigital in a windows server I'd like to transfer over. Also, being that I have a new build, I haven't assigned an array just yet but I have precleared all the drives and shut the pc down. I'm expecting another shipment of drives in the mail next week and wanted to just get all the preclearing out of the way before I started transferring data. Not sure if what I said made sense I'm working on 3 hours of sleep and my brain is fried but figured if I didn't ask this now I'd definitely forget.

 

I appreciate any help.

It is even more important.  (realizing it will erase all on the disk being precleared)
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Do I need to preclear every single drive coming into UnRaid? I mean I know you preclear the new ones you buy, but what about ones that are coming from a Windows build? I'm asking cause I have a 2 TB WDigital in a windows server I'd like to transfer over. Also, being that I have a new build, I haven't assigned an array just yet but I have precleared all the drives and shut the pc down. I'm expecting another shipment of drives in the mail next week and wanted to just get all the preclearing out of the way before I started transferring data. Not sure if what I said made sense I'm working on 3 hours of sleep and my brain is fried but figured if I didn't ask this now I'd definitely forget.

 

I appreciate any help.

 

I do not preclear disks that I have already precleared and am moving between servers.  But if I have a disk that has never been precleared, and I am not sure that every last byte on the drive has been tested, I would preclear it.

 

When in doubt, preclearing is always a good idea.

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After, the parity drive will slow down the transfer.  Install all your data drives, transfer files, then put in your parity drive.  

 

I always preclear anything going in the server, no downtime adding the drive, and plus, a used drive could have anything on it, deleting or formatting a drive doesn't actually erase the files.  Also, year three is when failure rate goes up, so its nice to catch marginal hardware. 

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Ok cool. Should I setup the parity drive before or after I move the data from my windows server? It's just under 6 tb's of media.

If you value speed, then after.  If you value your data, before.

 

If you want the fastest speed when initially loading the array, do not assign a parity disk.  The downside of this is that you will not know if the data that was written to the data disk can be read back until you go to use it, or verify with a checksum, or install a parity disk.    (un-readable sectors are only detected when reading from the disk, not when writing to it. )

If a disk sector is unreadable when you initially calculate parity, you will have lost that sector.

 

If you don't mind a slower load of data, then assign a parity drive FIRST.  The process of calculating parity automatically reads the target sectors first, then writes them.  This will allow the SMART firmware on the disk to mark an un-readable sector and re-allocate it upon the subsequent write.   You will not lose the data written.

 

Personally, I would never load an array with data without a parity drive installed.

 

You can team the faster initial load speed with a subsequent validation pass and subsequent install of a parity disk...

(load the array, then read it all and compare to the original source disks, then fix as needed)  It all depends on your needs and time requirements.

 

Joe L.

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Do I need to preclear every single drive coming into UnRaid?

Nope, preclear is not a requirement or it would be part of unraid. I have never precleared any of my drives and they all work fine.

 

Actually emhttp "preclears" a drive before adding it to the array if it has not been configured to be in the array already.

I.E. it writes 0's to the whole drive, writes a signature, then adds it into the array.

 

The benefit of Joe L's preclear is it can be done while the array is active and and it tests the drive and provides multiple passes.

 

Even some new drives could have bad sectors, so a read/write/read preclear can detect issues before you even start writing to the array.

It has saved me a few times from adding a questionable drive into the array.

 

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Excellent to know. So Raj gave me a setup idea, I have a 4220, and that is what I am going with. On the first row I'm doing the following

 

Slot 1                                              Slot 2                        Slot 3                        Slot 4

Parity <Hitachi Deskstar 7k3000 7200> Data <Hitachi Coolspin> Data <Hitachi Coolspin> Cache <Hitachi Deskstar 7k3000 7200>

 

Now I read the cache would help the write performance and I would still have my parity drive to ensure everything is getting calculated properly and all my media will be functional. Now my only although my setup is exactly like the above the drive lettering is all screwed up. I would think slot one would be /dev/sdb but instead it's /dev/sde. I was reading this thread regarding moving harddrives. They also mention in there how to do it via the devices page. Is this the proper route I should be going?

 

Thanks again for all your patience, and help.

 

 

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