Re: Turn off amgtar sparse detection for better performance

--000000000000998e7a062174efb7
Content-Type: text/plain; charset="UTF-8"

Thank you for the amazing tip. I also benchmarked similar results: amgtar
was averaging 140MB/s with --sparse, and with sparse disabled it now
averages 600MB/s. I expect this will have a huge improvement on backup
times.

On Sat, 31 Aug 2024 at 10:57, Exuvo <[email protected]> wrote:

> I have been trying to figure out why tar run by amanda was so much slower
> than my manual tar runs.
> The culprit is tar --sparse (which is on by default in amgtar) which for
> me maxes out 1 CPU core and reduces tar's read speed to around 130MB/s for
> me on a ZFS filesystem with 1GB files.
> I turned that option off and now it can read at 500MB/s with only 30% CPU
> usage.
>
> I suspect this will also resolve the slow read speeds i have with lots of
> tiny files as tar was also capped on CPU there but i had assumed it was
> blocking on IO.
>
> --
> Anton "exuvo" Olsson
>     [email protected]
>
>

--000000000000998e7a062174efb7
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Thank you for the amazing tip. I also benchmarked similar =
results: amgtar was averaging 140MB/s with --sparse, and with sparse disabl=
ed it now averages 600MB/s. I expect this will have a huge improvement on b=
ackup times.<br><br><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gm=
ail_attr">On Sat, 31 Aug 2024 at 10:57, Exuvo &lt;<a href=3D"mailto:exuvo@e=
xuvo.se" target=3D"_blank">[email protected]</a>&gt; wrote:<br></div><blockquo=
te class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px =
solid rgb(204,204,204);padding-left:1ex">I have been trying to figure out w=
hy tar run by amanda was so much slower than my manual tar runs.<br>
The culprit is tar --sparse (which is on by default in amgtar) which for me=
 maxes out 1 CPU core and reduces tar&#39;s read speed to around 130MB/s fo=
r me on a ZFS filesystem with 1GB files.<br>
I turned that option off and now it can read at 500MB/s with only 30% CPU u=
sage.<br>
<br>
I suspect this will also resolve the slow read speeds i have with lots of t=
iny files as tar was also capped on CPU there but i had assumed it was bloc=
king on IO.<br>
<br>
-- <br>
Anton &quot;exuvo&quot; Olsson<br>
=C2=A0 =C2=A0 <a href=3D"mailto:[email protected]" target=3D"_blank">exuvo@exu=
vo.se</a><br>
<br>
</blockquote></div></div>

--000000000000998e7a062174efb7--