[oi-dev] [developer] Improving file transfer speed on ZFS

[Peter Tribble]

On Tue, Nov 4, 2025 at 4:03 AM Atiq Rahman <atiqcx at gmail.com> wrote:

> Hi,
> When I am copying over files to the zfs dataset on an external HDD, the
> speed is one third of what it is over exFAT. This is zfs to zfs copy which
> is basically way slower than zfs to exFAT.
>

What speed are you actually getting? Both from the perspective of how long
the
copy takes, but also from iostat.

I do this, and see transfer speeds that are either limited by the capacity
of USB2, or
the drive itself if I have a USB3 port.


> This was my zpool create command on the external drive,
>
> ```
> zpool create -o ashift=12 -O compression=lz4 -o autotrim=off -O
> mountpoint=none -O atime=off -O dnodesize=auto hyperspace /dev/dsk/c4t0d0
> ```
>
> And, this is how the dataset was created:
>
> ```
> zfs create -o recordsize=1M -o normalization=formD -O mountpoint=/media
> hyperspace/media
> ```
>
> I know zfs has journaling overhead. But, is it possible to set certain zfs
> properties to improve the transfer speed?
>

Journaling normally speeds things up.

But generally I would start with using the defaults (except compression),
other settings generally
only come into play in specialist cases.


>
> Best!
>
> Atiq
>
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-- 
-Peter Tribble
http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/
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