Re: [gentoo-user] Testing a used hard drive to make SURE it is good.

[Dale]

Michael wrote:
> On Tuesday, 16 June 2020 12:26:01 BST Dale wrote:
>
>> From what I've read, I agree.  Basically, as some have posted in
>> different places, SMR drives are good when writing once and leaving it
>> alone.  Basically, about like a DVD-R.  From what I've read, let's say I
>> moved a lot of videos around, maybe moved the directory structure
>> around, which means a lot of data to move.  I think I'd risk just
>> putting a new file system on it and then backup everything from
>> scratch.  It may take a little longer given the amount of data but it
>> would be easier on the drive.  It would keep it from hammering as you
>> put it that drive to death.
>>
>> I've also read about the resilvering problems too.  I think LVM
>> snapshots and something about BTFS(sp?) has problems.  I've also read
>> that on windoze, it can cause a system to freeze while it is trying to
>> rewrite the moved data too.  It gets so slow, it actually makes the OS
>> not respond.  I suspect it could happen on Linux to if the conditions
>> are right.
>>
>> I guess this is about saving money for the drive makers.  The part that
>> seems to really get under peoples skin tho, them putting those drives
>> out there without telling people that they made changes that affect
>> performance.  It's bad enough for people who use them where they work
>> well but the people that use RAID and such, it seems to bring them to
>> their knees at times.  I can't count the number of times I've read that
>> people support a class action lawsuit over shipping SMR without telling
>> anyone.  It could happen and I'm not sure it shouldn't.  People using
>> RAID and such, especially in some systems, they need performance not
>> drives that beat themselves to death.
>>
>> My plan, avoid SMR if at all possible.  Right now, I just don't need the
>> headaches.  The one I got, I'm lucky it works OK, even if it does bump
>> around for quite a while after backups are done.
>>
>> My new to me hard drive is still testing.  Got a few more hours left
>> yet.  Then I'll run some more tests.  It seems to be OK tho.
>>
>> Dale
>>
>> :-)  :-)
> Just to add my 2c's before you throw that SMR away, the use case for these
> drives is to act as disk archives, rather than regular backups.  You write
> data you want to keep, once.  SMR disks would work well for your use case of
> old videos/music/photos you want to keep and won't be overwriting every other
> day/week/month.  Using rsync with '-c' to compare checksums will also make
> sure what you've copied is as good/bad as the original fs source.


I try to update about once a day, that way the changes or additions are
fairly small.  On occasion tho, I find a better version of a video which
means I have a new file and delete the old.  That may make it a little
harder for the SMR drive but the amount of data, given my slow DSL, is
not large enough to matter.  I think the biggest changes rsync has
reported so far, about 4 or 5GBs or so. 

My general process is like this.  I find a point where I can backup.  I
power up the external drive, mount it using KDE's Device Notifier, use
rsync to update the files and then unmount the drive with DN.  After
that, I let it sit until I notice that it is not doing that bumping
thing for a bit.  Sometimes that is a couple minutes, sometimes it is 10
or 15 minutes or so.  Generally, it isn't very long really.  Sometimes I
go do something else, cook supper, mow the grass or whatever and cut it
off when I get back. 

In theory I could cut it off right after the backup is done and I've
unmounted it.  Thing is, the changes will build up depending on how
large the cache/buffer/whatever is that it stores as CMR.  From what
I've read, it has a PMR/CMR section and then the rest is SMR.  It writes
new stuff to the PMR/CMR section and when it has time, it moves it to
the SMR parts.  It then does its rewrite thing with the shingles.  I'm
sort of making it simple but that's what some have claimed it does. 

Let's keep in mind, the drive I just bought in this thread is a PMR
drive.  The SMR drive is one I've had a while in a external enclosure. 
Most of the time, it holds my desk down and a stack of Blu-ray discs
up.  That bumpy thing sometimes makes the discs fall off tho.  I need to
clean my desk off, again. 

While I wish my backup drive wasn't a SMR, at least it is acceptable in
performance for what I'm using it for.  If I had spent money on that
drive and put it on /home, then I'd be pretty upset.  We're talking
steam and smoke upset.  It's not like these drives are $20 or $30 or
something.  I got a good deal paying about $150 for this latest new to
me drive.  Still, that's $150 that I don't want to waste on something
that can't handle what I do.  Backup drive that is SMR, well, OK.  I'm
not really pleased about it but it works OK.  Having it on /home where
it could cause my system to freeze or something, well, that may remind
me of the hal days.  I'm sure some recall me and my love for hal.  I
don't like going there.  Moving on.

Later on, I may run up on a deal and replace the drive and do something
else with the SMR I got.  I'm not sure what but SMR is good for a couple
things at least, sort of.  lol  May find a 10TB, or even a 12.  Who knows. 

Time to go feed the deer.  They miss me when I don't go for a walk in
the woods.  ;-)

Dale

:-)  :-)