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Re: ZFS'ing my T5120 with Debian

On 26 May 2018, at 17:08, Chris Ross <cross+debian@distal.com> wrote:
> On Fri, May 25, 2018 at 11:39:49PM +0200, John Paul Adrian Glaubitz wrote:
>> On 05/25/2018 09:38 PM, Chris Ross wrote:
>>> root@t5120:/var/tmp# grub-install /dev/sda
>>> Installing for sparc64-ieee1275 platform.
>>> grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible.
>>> grub-install: error: filesystem `zfs' doesn't support blocklists.
>>> root@t5120:/var/tmp# 
>> That error message is quite clear: You have to set up a separate non-ZFS
>> partition which serves as a boot partition. Booting from a ZFS partition
>> using blocklists doesn't work.
> Though, the conversation earlier covered that grub supports ZFS.  You say above
> that booting from a ZFS partition using blocklists doesn't work.  There's
> something I'm not understanding in the space across those two statements.

I think the problem is that "grub supports ZFS" is a somewhat vague statement
with two possible interpretations:

1. Grub can be installed to a ZFS partition (i.e. the small stage 0, or whatever it
   is on SPARC, can locate the main grub binary when stored in a ZFS partition)

2. Grub can load kernels and initrds from a ZFS partition

Given the error message you have received, it seems that only the second of
these points is true, which is not that surprising. ZFS is a complicated file
system, and therefore likely requires a significant amount of code to parse,
which is not included in the initial loader. However, the main grub binary can
be fairly large, or even load additional modules, allowing it to include more
complicated features like ZFS support.


> FreeBSD has a zfsbootloader, which is what I've been using.  And, whether
> I can use ZFS or not, I don't think I want to start down the path of booting
> from magnetic media that isn't replicated onto another spindle.  If debian
> will let me boot from ZFS, how do I do it?  If it won't, are there other options
> to boot from mirrored filesystems?
>> Btw, I'm surprised to read that the T5120 supports GPT disk labels? I
>> thought that GPT is supported on T4 and newer only.
> I believe the same, I don't know what that error message means.  I know that
> I do have sun labels, not GPT labels, on my disks.
>          - Chris

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