Re: [gentoo-user] External hard drive and idle activity

[madscientistatlarge]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, January 2, 2020 12:12 PM, Rich Freeman <rich0@g.o> wrote:

> On Thu, Jan 2, 2020 at 1:41 PM Dale rdalek1967@×××××.com wrote:
>
> > Rich Freeman wrote:
> >
> > > Out of curiosity, what model drive is it? Is it by chance an SMR /
> > > archive drive?
> >
> > Device Model: ST8000AS0003-2HH188
> > I recall reading about SMR but can't recall the details of what it is.
> > As far as I know, this is just a basic 8TB drive.
>
> This is an SMR drive. You should DEFINITELY read up on what they are.
>
> For reads they're completely normal. For sequential writes to unused
> space they're completely normal. For random writes or overwrites they
> are significantly different from traditional hard drives.
>
> They work a bit like an SSD in the sense that blocks are arranged into
> larger erase regions. Within a region blocks can only be written
> sequentially. If you want to overwrite one block in the middle of a
> region, the drive will read the entire region into RAM, then write the
> entire region sequentially with the overwritten block to a new spot on
> the disk. This is just like in an SSD where if try to overwrite a
> block in a region with any unTRIMmed blocks the drive must read the
> entire region, erase the region, and write the modified region.
>
> Except that in an SSD those extra reads/writes operate with SSD access
> times. With an SMR drive those extra reads/writes operate with hard
> drive latencies, so they're MUCH more costly.
>
> For backup use they're usually fine, IF you're writing in a sequential
> file format that is appended to. If you're using rsync to do your
> backups then that isn't what you're doing and you're probably paying a
> heavy penalty. If you were doing incremental backups using
> tar/duplicity/whatever then you'd probably be fine.
>
> Some filesystems might be optimized for these drives to reduce the
> amount of overwriting in place. I haven't looked into it. I'd expect
> a log-based filesystem to work fairly well, though those can have high
> levels of fragmentation which is better suited for SSD than SMR.
>
> These drives all have fairly active firmware that manages this special
> overwrite process so that they can be used with operating systems that
> are naive to how they work. I wouldn't be surprised if this is what
> is causing the drive to be active after you unmount it. In theory it
> should be harmless to power it off. However, leaving it powered on
> probably will improve its performance as it can take care of any
> garbage collection before the next time you use it. If whatever
> journal it is using to speed things up gets full then you'll feel the
> full brunt of any write penalties until it is flushed.

> Rich

Thank you for the excellent education!  I haven't read the full thread but I'd also suggest that running Wireshark on the USB port would likely help diagnose any other issues.  I'm having similiar problems with an external drive "freeezing" and refusing to unmount normally and this will be my next step to diagnose it.