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Date:      Wed, 24 Apr 2019 19:19:07 +0300
From:      Igor Kozhukhov <igor@dilos.org>
To:        openzfs-developer <developer@lists.open-zfs.org>
Cc:        illumos-zfs <zfs@lists.illumos.org>, Matthew Ahrens <mahrens@delphix.com>, developer <developer@open-zfs.org>, zfs-devel@list.zfsonlinux.org, zfs-devel@freebsd.org, freebsd-fs <freebsd-fs@freebsd.org>, zfs-discuss <zfs-discuss@zfsonlinux.org>
Subject:   Re: [developer] Re: [zfs] Re: April OpenZFS Leadership Meeting
Message-ID:  <4C9A42C6-5024-4A87-A45C-A43A4562C3BA@dilos.org>
In-Reply-To: <D263427E-9575-49EE-80F0-489A1C9B321E@cos.ru>
References:  <CAJjvXiE%2B27fYZh-RUmE=mjD4N63TrnTQVb65qaPZDj4K6oS-Rg@mail.gmail.com> <CAJjvXiE7y%2BYXAZCewDKNKXCmvMYhh4Fy0wt8Kh8V21WvYz3opg@mail.gmail.com> <CAJjvXiHhhZcg_4Ju1U1F9UWRxbNyJyDdnxp89CnBCQpWvqO4xw@mail.gmail.com> <CAJjvXiG4xB76c5p6OVmu9-zVz47DCcmPs%2BT0TUvMf572WXtNxw@mail.gmail.com> <CAJjvXiGXzxu0KiJ1eEHpcpM_o-L6zK-Kd=J2QjXC2wQsMR3Szg@mail.gmail.com> <CAJjvXiEU5385vkR15qiEM1uO-Jmo5ST0uh-t9%2B9O0k-_=NWz2g@mail.gmail.com> <D263427E-9575-49EE-80F0-489A1C9B321E@cos.ru>

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>=20
> For anecdotal experience regarding root pool compression, the issue =
was there with older GRUB loader of OpenSolaris and contemporary Solaris =
10; I believe it was fixed in the illumos branch after the fork (can't =
find and point to a commit now, possibly soon after lz4 introduction; no =
idea about state of later Solaris releases).
>=20
> The problem manifested by GRUB refusing to read datasets (rpool, =
rpool/ROOT, rpool/ROOT/$BENAME) that had the compression enabled (even =
if no blocks were in fact compressed) or disabled at the moment but =
compressed blocks encountered during a read.
>=20
> This was one of main reasons early on for my split-root support =
scripts, so /usr could be separated into a gzip-9'ed dataset and shrink =
from ~3gb to ~1gb on a default install.
>=20
> On my current laptop I see rpool has compression=3Doff, rpool/ROOT has =
lz4 and rootfs(es) inherit that. Works well WRT stability and =
performance.

it is known issue with compression=3Don on rpool, but it is know working =
scenario for compression=3Don rpool/ROOT as dataset with root fs - it is =
working fine on Intel and SPARC
it is why i tried to explain to: do not use compression=3Don on pool =
itself , but use it on dataset where root file system available =3D =
rpool/ROOT and inherit to BE in rpool/ROOT/*.

but my English is not good in this context.

-Igor

>=20
> Hope this helps,
> Jim
>=20
> --
> Typos courtesy of K-9 Mail on my Android
>=20
> ------------------------------------------
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