ZFS - Abyssal slow on copying

[O. Hartmann]

Am Sun, 2 Oct 2016 15:30:41 -0400
Allan Jude <allanjude at freebsd.org> schrieb:

> On 2016-10-02 15:25, O. Hartmann wrote:
> > 
> > Running 12-CURRENT (FreeBSD 12.0-CURRENT #32 r306579: Sun Oct  2 09:34:50 CEST 2016
> > ), I have a NanoBSD setup which creates an image for a router device.
> > 
> > The problem I face is related to ZFS. The system has a system's SSD (Samsung 850 Pro,
> > 256GB) which has an UFS filesystem. Aditionally, I have also a backup and a data HDD,
> > both WD, one 3 TB WD RED Pro, on 4 TB WD RED (the backup device). Both the sources for
> > the NanoBSD and the object tree as well as the NANO_WORLDDIR are residing on the 3 TB
> > data drive. 
> > 
> > The box itself has 8 GB RAM. When it comes to create the memory disk, which is ~ 1,3
> > GB in size, the NanoBSD script starts creating the memory disk and then installing
> > world into this memory disk. And this part is a kind of abyssal in terms of the speed.
> > 
> > The drive sounds like hell, the heads are moving rapidly. The copy speed is incredibly
> > slow compared to another box I usually use in the lab with UFS filesystem only
> > (different type of HDD).
> > 
> > The whole stuff the nanbsd is installed from and to is on a separate ZFS partition,
> > but in the same pool as everything else. When I first setup the new partitions, I
> > switched on deduplication, but I quickly deactivated it, because it had a tremendous
> > impact on the working speed and memory consumption on that box. But something seems
> > not right since then - as I initially described, the copy/initialisation
> > speed/bandwith is abyssal. Well, I also fear that I did something wrong when I firt
> > initialised the HDD - there is this 125bytes/4k block discussion and I do not know
> > how to check whether I'm affected to that or not (or even causing the problems) and
> > how to check whether DEDUPLICATION is definitely OFF (apart from the usual stuff list
> > features via "zfs get all").
> > 
> > As an example: the nanbosd script takes ~ 1 minute to copy /boot/loader from source to
> > memory disk and the HDD makes sounds like hell and close to loosing the r/w heads. On
> > other boxes this task is done in a blink of an eye ...
> > 
> > Thanks for your patience,
> > 
> > Regards,
> > oh
> >   
> 
> Turning deduplication off, only stops new blocks from being
> deduplicated. Any data written while deduplication was on, are still
> deduplicated. You would need to zfs send | zfs recv, or
> backup/destroy/restore to get the data back to normal.
> 
> If the drive is making that much noise, have you considered that the
> drive might be failing?
> 

Hello.

Might there be any hint I can investigate on that ZFS partition showing me that the
particular partition is still doing deduplication? If I wouldn't know that I switch
dedup on and later off, I would blame the OS instead. So, for further forensik analysis
in the future, it would be nice to know how to look at it - if it is doable via simple
checking the features of the ZFS partition ...

Thanks,
oh 
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