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I recently received a batch of 6 brand new HGST He8 drives and when running an initial long self-test on them, I noticed that the extended self-test routine recommended polling time exhibit a very large degree of variability. 

for f in /dev/sd[u-z]; do sudo smartctl -i $f | grep "Model"; done
Device Model:     HGST HUH728080ALN600
Device Model:     HGST HUH728080ALN600
Device Model:     HGST HUH728080ALN600
Device Model:     HGST HUH728080ALN600
Device Model:     HGST HUH728080ALN600
Device Model:     HGST HUH728080ALN600

for f in /dev/sd[u-z]; do sudo smartctl -a $f | grep -A1 "Extended self-test"; done
Extended self-test routine
recommended polling time:    (1367) minutes.
Extended self-test routine
recommended polling time:    (1217) minutes.
Extended self-test routine
recommended polling time:    (1242) minutes.
Extended self-test routine
recommended polling time:    (1133) minutes.
Extended self-test routine
recommended polling time:    (1167) minutes.
Extended self-test routine
recommended polling time:    (1083) minutes.

Has anyone seen variability like this with their drives or have any explanation as to what would cause such a massive range?

user429673
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1 Answers1

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HDDs are very complex mechanincal devices. While they are advertised as, for example, 7200 RPM disks, each single disk has its own specific rotation speed (eg: 7170 or 7220 RPM). The same can be said for the voice-coil actuator and other servos.

In short, two disks from the same model/batch are very similar, but not really identical.

For the records, I observed similar discrepancies on SMART long self test polling time on 2x Seagate 4TB NAS disks.

shodanshok
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