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As simple as the title suggests.

/dev/sda is a unit from /dev/md127 - RAID1 drive.

I'm currently running a test - started a smartctl -t long /dev/sda.

Afterwards, I started to copy files over WinSCP (SFTP) to the mounted mdadm array.

I didn't notice any performance drops, but I'm kind of not sure - not a system administrator, am just developing an automated system.

Is it safe to "use" (write/read) disk while the drive is undergoing a smartcheck? What can go wrong? Are there any drawbacks?

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Interesting question. I would definitely guess that it's perfectly safe, as the SMART check shouldn't touch any on-disk data and would only use the disk's idle time, but an authoritative answer would be really nice. – Michael Kjörling Aug 13 '13 at 14:53
up vote 2 down vote accepted

Yes, it is safe, as the checks do not modify anything on your disk and thus will not interfere with your normal usage (I happen to be researching the topic right now). I have managed servers with smart checks running and never had to worry about using the disks at the same time.

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Okay, won't interfere with normal usage, what'd count as abnormal usage? My scenario might have ~10 IP cameras writing to disks at 2MP per frame - how about this? – joltmode Aug 14 '13 at 7:34
I would consider it normal when the disk is performing is satisfactory as far as your application is concerned and what it is designed to do, i.e., the disk is still usable and your application runs fine and you do not see logs filled up with I/O errors. In the latter case it would become a stress test and thus abnormal. A disk designed for the server environment is quite different from one that you get from Frys to back up your pictures, and thus what is normal for one disk may be abnormal for another. – johnshen64 Aug 14 '13 at 15:02

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