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supermoocow

Quick question: preclear and parity checks

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Hi all,

 

I've built my system and have lots of data on it but haven't pre-cleared the drives.

 

If I do regular (monthly) parity checks does the mitigate the risk of not having pre-cleared the drives?

 

Thanks in advance!

 

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Hi all,

 

I've built my system and have lots of data on it but haven't pre-cleared the drives.

 

If I do regular (monthly) parity checks does the mitigate the risk of not having pre-cleared the drives?

 

Thanks in advance!

Yes. Just be sure to get smart reports on all drives now, and after each check and watch for changes. Since unraid only tolerates one dead drive at a time, don't risk running on a known marginal drive. A successful preclear doesn't guarantee good drives, so this advice applies whether or not you precleared. Periodic smart checks are just good practice when dealing with a storage array.

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Hi all,

 

I've built my system and have lots of data on it but haven't pre-cleared the drives.

 

If I do regular (monthly) parity checks does the mitigate the risk of not having pre-cleared the drives?

It proves you can read the drives, it does nothing to prove you can write to them until you actually fill any given sector with data and then successfully read it back.

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Thanks, so just to clarify;

 

If I run a parity check and don’t add any files I should be confident the files are ok?

 

If I subsequently add files I won’t know this data is ok until after I run another parity check?

 

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If I subsequently add files I won’t know this data is ok until after I run another parity check?

Once a parity disk is added and initial parity calculated, to write a new file requires reading both the parity disk and data disk sectors prior to writing them with their new respective contents.

 

Therefore, it is far less risk the disk sectors are not readable. 

 

Joe L.

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Thanks, so just to clarify;

 

If I run a parity check and don’t add any files I should be confident the files are ok?

Yes. But not needed during normal use.

 

If I subsequently add files I won’t know this data is ok until after I run another parity check?

No. The data is OK after being written. The parity system verifies sector readability just before the data is written.

 

After any physical disk is added or changed a parity check verifies the written content. They are not needed in normal use after writing data files. A monthly parity check is recommended.

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