Consistancy check

[Raided]

I have a AS-608T I recently swapped some disks out for bigger disks and towards the end of the rebuild i started getting media errors i was wondering if i could check the integrity of the data?

[orion]

I cannot find UI function for RAID integrity check. However you can issue this check by manual commands. You can refer to the web page: https://www.thomas-krenn.com/en/wiki/Mdadm_checkarray

Basically you can get md status of all of your RAID devices:

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cat /proc/mdstat

Select the md device that you plan to check, for example, md1. Then show the current mismatch count under /sys/block/md1/md/mismatch_cnt before you start. Here is the command to start integrity check:

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echo check > /sys/block/md1/md/sync_action

After done, show "mismatch_cnt" again.

[Kapitein Haak]

Hello Orion,
I would guess this checks the integrity of the raid set. When media errors occured, faulty data might be copied to the new (likely flawless) raid set. The only way to check the data is to bit or hash compare it to a known good copy of the data. This might be a lengthy processen.

Best regards,
Kapitein Haak.

[Raided]

Thanks how do i enter these manual commands on the asustor nas?

[orion]

Hello Orion,
I would guess this checks the integrity of the raid set. When media errors occured, faulty data might be copied to the new (likely flawless) raid set. The only way to check the data is to bit or hash compare it to a known good copy of the data. This might be a lengthy processen.

Best regards,
Kapitein Haak.

Hello Kapitein,

Yes, it'll generate re-sync event internally (md driver). In case that there is a fault integrity, for example parity error under RAID-5, it will update mismatch count. Usually we should get a read error on certain disk in this condition. "md" will re-generate correct data and try to write to the specific sector to correct this error. It indeed takes long time to check the whole volume.

[orion]

Thanks how do i enter these manual commands on the asustor nas?

You can install "Shell In A Box" application under ADM AppCentral, or use putty under your PC. You'll need to enable terminal service under ADM web -> Services -> Terminal -> Enable SSH service. You should login to NAS as root account (the password is the same as admin). After that, you can use those commands.

[Raided]

Great ill try that on the weekend. Just one more question i replaced another disk if it rebuilds without errors does that mean there's no problems or will it just transfer over the data without knowing its corrupt?

[orion]

Great ill try that on the weekend. Just one more question i replaced another disk if it rebuilds without errors does that mean there's no problems or will it just transfer over the data without knowing its corrupt?

In the following condition, your data should be safe.

• Remove old disk and insert one bigger disk (HDD-A).
• Media error on HDD-A.
• Remove HDD-A and replace it with another bigger disk (HDD-B).
• Rebuilding process completed successfully.

I believe it is the condition. Or you should see error messages under ADM.

[Raided]

Great thanks for your help ill do the integrity check just to be 100% sure its good

[Raided]

Ok i gave it a try but the first command doesn't really tell me anything i don't already know and the second says access is denied?

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