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Date:      Mon, 3 Oct 2016 11:30:50 +0200
From:      "O. Hartmann" <ohartman@zedat.fu-berlin.de>
To:        Allan Jude <allanjude@freebsd.org>
Cc:        freebsd-current@freebsd.org
Subject:   Re: ZFS - Abyssal slow on copying
Message-ID:  <20161003113050.0f1b09bd.ohartman@zedat.fu-berlin.de>
In-Reply-To: <ae0af48b-b462-876e-4139-a6fcc2836794@freebsd.org>
References:  <20161002212504.2d782002.ohartman@zedat.fu-berlin.de> <ae0af48b-b462-876e-4139-a6fcc2836794@freebsd.org>

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

> On 2016-10-02 15:25, O. Hartmann wrote:
> >=20
> > 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.
> >=20
> > The problem I face is related to ZFS. The system has a system's SSD (Sa=
msung 850 Pro,
> > 256GB) which has an UFS filesystem. Aditionally, I have also a backup a=
nd 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 residi=
ng on the 3 TB
> > data drive.=20
> >=20
> > The box itself has 8 GB RAM. When it comes to create the memory disk, w=
hich 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 term=
s of the speed.
> >=20
> > The drive sounds like hell, the heads are moving rapidly. The copy spee=
d is incredibly
> > slow compared to another box I usually use in the lab with UFS filesyst=
em only
> > (different type of HDD).
> >=20
> > The whole stuff the nanbsd is installed from and to is on a separate ZF=
S partition,
> > but in the same pool as everything else. When I first setup the new par=
titions, 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 som=
ething 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 p=
roblems) and
> > how to check whether DEDUPLICATION is definitely OFF (apart from the us=
ual stuff list
> > features via "zfs get all").
> >=20
> > 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 ...
> >=20
> > Thanks for your patience,
> >=20
> > Regards,
> > oh
> >  =20
>=20
> 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.
>=20
> If the drive is making that much noise, have you considered that the
> drive might be failing?
>=20

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 foren=
sik 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=20

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