Re: smartmontools query

Answers are inline. I'm also sending you a paper I wrote on hard drive 
testing off-list. It should help you get up to speed.

On 2/27/2015 3:43 AM, radiatejava wrote:
> I have few doubts with smartmontools, can someone clarify ?
Smartmontools doesn't do any tests. It just tells the hard drive to run 
the tests built into the firmware and reads the results. It is up to the 
user to interpret the results.
>
> 1. Shall I rely on smartctl -H <dev> to see if the device is in good
> health ? Or do I need to do further selftest, short or long test ? My
> aim is just to find if the disk is fine or not for read and write. We
> have a high availability solution and we want to use this utility to
> failover to standby node in case of any issue with the disk.

Short answer, no. By the time the SMART health status trips to bad, your 
chance of getting data back off is very low. I've done it on such a 
drive, but not every time, and those times it did work, I didn't get 
100%. More like 70%.
>
> 2. Health check with -H option or selftest or short test – are they
> handled by the device driver independently ? Or they consume some CPU
> cycles ? Any data read or write is involved to run these tests that
> takes CPU times ?

All the tests you mention are handled by the hard drive's firmware. So 
in a way, yes it is independent. As the tests are done by the hard 
drive, there is no CPU usage, other than what is required to run 
smartmontools. Also remember that the short (and long) test results can 
be deceptive if you don't know how to read them.
>
> 3. What exactly -H checks ?

Depends on the firmware, but in general, each drive has multiple 
attributes. Each attribute has a threshold. -H is checking if any 
threshold has tripped.
>
> Appreciate reply, thanks!
>
>


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