Re: misleading ZFS warning

I think it largely is for RAIDZn set ups, which will be severely impacted
in turns of utilization for small volblocksizes. It will still impact
compression performance: with 4K volblocks and ashift=12,
 you’ll have no ability to leverage compression.

- Eric

On Thu, Jul 23, 2026 at 1:43 AM Ronald Klop <ronald-lists@klop.ws> wrote:

> For a single disk pool I think you can ignore the warning. I can only
> imagine the situation of the warning for a raidz setup.
>
> Maybe others have more insights.
>
>
> Regards,
> Ronald
>
> *Van:* Anthony Pankov <anthony.pankov@yahoo.com>
> *Datum:* 22 juli 2026 17:26
> *Aan:* Ronald Klop <ronald-lists@klop.ws>
> *CC:* fs@FreeBSD.org
> *Onderwerp:* Re: misleading ZFS warning
>
>
> >  What is underlying pool structure?
>
>  pool: as1
>  state: ONLINE
> config:
>
>         NAME                           STATE     READ WRITE CKSUM
>         as1                            ONLINE       0     0     0
>           diskid/DISK-WD-C82MNNSK.eli  ONLINE       0     0     0
>
> one dedicated GELI-encrtypted HDD.
>
> GELI info:
>
> Geom name: diskid/DISK-WD-C82MNNSK.eli
> State: ACTIVE
> EncryptionAlgorithm: AES-XTS
> KeyLength: 128
> Crypto: accelerated software
> Version: 7
> UsedKey: 0
> Flags: NONE
> KeysAllocated: 1398
> KeysTotal: 1398
> Providers:
> 1. Name: diskid/DISK-WD-C82MNNSK.eli
>    Mediasize: 6001175121920 (5.5T)
>    Sectorsize: 4096
>    Mode: r1w1e1
>
>
>
> Wednesday, July 22, 2026, 6:12:00 PM, you wrote:
>
> > What is underlying pool structure?
> > Zraid/mirror/single disk?
>
> > If zraid, what is the stripesize?
>
> > Regards,
> > Ronald
>
> > Van: Anthony Pankov
> > Datum: 22 juli 2026 11:51
> > Aan: fs@FreeBSD.org
> > Onderwerp: misleading ZFS warning
>
> >> > > Hello,
> >> > Doing this:
> >> >  zfs create  -b 4096 -o volmode=dev  -V 32G as1/dockerim/dsk.adocker
> >> > I've got
> >> > Warning: volblocksize (4096) is less than the default minimum block
> size (16384).
> >> To reduce wasted space a volblocksize of 16384 is recommended.
> >> > While ashift=12 for this pool I can't understand am I really do
> something wrong and there will be "wasted space" or this is a misleading
> warning.
> >> > Can somebody enlight this?
> >> > -- > Best regards,
> >>  Anthony Pankov                         mailto:anthony.pankov@yahoo.com
>
>
>
> --
> Best regards,
> Anthony
>
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