Does Smartctl Selftest Involves Read/Write Operations on the disk itself?

S

shinx

Hi all, please correct me if this is not the right place to post this question.

I would like to know if smartctl self-test involves some read/write operations on the disk itself.

From what I understand from the Wikipedia, it does involves read/write operations.

Short - Checks the electrical and mechanical performance as well as the read performance of the disk. Electrical tests might include a test of buffer RAM, a read/write circuitry test, or a test of the read/write head elements. Mechanical test includes seeking and servo on data tracks. Scans small parts of the drive's surface (area is vendor-specific and there is a time limit on the test). Checks the list of pending sectors that may have read errors, and it usually takes under two minutes.

Long/extended - A longer and more thorough version of the short self-test, scanning the entire disk surface with no time limit. This test usually takes several hours, depending on the read/write speed of the drive and its size.
Click to expand...

However, when I run a short/long test on the drive itself. I do not see any iops on the disk from the gstat

Code: 
$ sudo smartctl -l selftest /dev/da0
smartctl 6.6 2017-11-05 r4594 [FreeBSD 11.2-STABLE amd64] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF READ SMART DATA SECTION ===
Self-test execution status:             68% of test remaining
SMART Self-test log
Num  Test              Status                 segment  LifeTime  LBA_first_err [SK ASC ASQ]
     Description                              number   (hours)
# 1  Background long   Self test in progress ...   -     NOW                 - [-   -    -]
# 2  Background long   Completed                   -   14148                 - [-   -    -]
# 3  Background short  Completed                   -   14128                 - [-   -    -]

Long (extended) Self Test duration: 39236 seconds [653.9 minutes]

Code: 
dT: 0.002s  w: 1.000s  filter: da0
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w    d/s   kBps   ms/d   %busy Name
    0      0      0      0    0.0      0      0    0.0      0      0    0.0    0.0| da0

Thanks in advance.
 
Ok.
But, will it affect the performance of the disk if I run a SHORT/LONG Self-test on a running disk with high IOPS?
 
shinx said:
But, will it affect the performance of the disk if I run a SHORT/LONG Self-test on a running disk with high IOPS?
Click to expand...
Never done any real tests but I would say yes. With the short tests probably not that much, the long tests might have some noticeable impact though. Although I do think you would need to have a 'normal' load that's close to the maximum IOPS the drive could push before you would actually notice it.
 
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