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Date:      Mon, 14 May 2018 20:55:05 +0000
From:      Paul Esson <paul.esson@redstor.com>
To:        Eric Borisch <eborisch@gmail.com>, =?iso-8859-1?Q?Karli_Sj=F6berg?= <karli@inparadise.se>
Cc:        "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>
Subject:   Re: Releasing deleted blocks from a sparse ZVOL
Message-ID:  <HE1PR0102MB2588BF153F2FB8DA604D7C519E9C0@HE1PR0102MB2588.eurprd01.prod.exchangelabs.com>
In-Reply-To: <CAMsT2=k%2BcW7GheH945rp-hX4Er6rpUvrRghXEgj1=VchdEotxQ@mail.gmail.com>
References:  <AM5PR0102MB2578E94BA1F8894339FEB93C9E9C0@AM5PR0102MB2578.eurprd01.prod.exchangelabs.com> <FCD89CD5-B86F-41EB-A30B-6ABF67D4630A@inparadise.se>, <CAMsT2=k%2BcW7GheH945rp-hX4Er6rpUvrRghXEgj1=VchdEotxQ@mail.gmail.com>

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Hi Eric,
Thanks for your feedback which sounds encouraging. I'll give that a try.

Regards,
Paul.E


Paul Esson | Redstor Limited
t +44 (0)118 951 5235
m +44 (0)776 690 6514
e paul.esson@redstor.com

________________________________
From: eborisch@alumni.stanford.edu <eborisch@alumni.stanford.edu> on behalf=
 of Eric Borisch <eborisch@gmail.com>
Sent: Monday, May 14, 2018 9:37:43 PM
To: Karli Sj=F6berg
Cc: Paul Esson; freebsd-fs@freebsd.org
Subject: Re: Releasing deleted blocks from a sparse ZVOL

I've had success in a similar config by attaching the zvol as 'ahci-hd', wh=
ich shows up as a 'BHYVE SATA DISK' in a BSD guest. With such a guest (runn=
ing a zpool on the attached device):

kstat.zfs.misc.zio_trim.failed: 0
kstat.zfs.misc.zio_trim.unsupported: 0
kstat.zfs.misc.zio_trim.success: 179883
kstat.zfs.misc.zio_trim.bytes: 13126696960

Also working with a linux guest.

I see the expected tracking of the 'logicalreferenced' size in the host wit=
h the ALLOC size in the guest (allowing for upward bias due to using 32k se=
ctor sizes on my zvols).

Note that TRIM and UNMAP are two extremely similar but distinct (used for S=
ATA & SCSI, respectively) commands. Both are commonly referred to as 'trim'=
 by layers above the device drivers.

  - Eric



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