[Paranoia] Parallel ripping causes extreme slowdowns

[Merlijn B.W. Wajer]

Hi,

I am running into similar issues, and I, too, am not sure how to
approach fixing this problem.

On 22/03/2019 12:56, Johannes Bauer wrote:
> On 17.03.19 22:55, Karl Heller wrote:
>> Try moving your card to a different slot.
> 
> Not possible, there's only one PCIe slot.
> 
> Regardless, the issue seems to only occur with cdparanoia; I've switched
> to cdda2wav and it works perfectly, even when using libparanoia. No idea
> why, but that's what I'm seeing.

I think if you run cdparanoia with paranoia disabled, you will see that
there are no slowdowns too, at least most of the time.

I am ripping CDs using whipper [1] (a morituri fork), which uses cdrdao
and cdparanoia. I've ripped a lot of CDs with a single drive, but need
to switch to multiple drives for various reasons [2].

I have four drives happily ripping at good speeds, but -- the moment
scsi read errors occur (or when cdrdao runs!), all the drives just slow
down to a halt.

My hardware setup is different from yours, but I think we're ultimately
seeing the same problem: insane slowdowns when one drive is having
difficulty reading some sector. I use USB<->SCSI converters (each on a
separate USB controller).

I would be up for doing to experiment on just one internal SATA
controller, but I'm not so sure it will make a big difference.

Wondering what tools can be used to debug these issues. What I can see
from usbtop is that most of the time when slowdowns occur, there is just
nothing happening on the USB buses, which indicate to me that there are
no saturation problems. Maybe there is useful information available in
the SCSI subsystem? (I was born after SCSI was published, so I'll have
some digging to do)

I wonder if it's somehow related to cache defeating - clearing the cache
of all the drives all the time, instead of just one drive?

Regards,
Merlijn


[1] https://github.com/whipper-team/whipper/

[2] The Internet Archive (archive.org) is digitising a lot of CDs. We've
digitised over 235000 CDs, and almost all with cdparanoia:
https://archive.org/details/acdc

We're going to move to audio books CDs now (we have containers full of
audio book CDs), which often have 9 CDs per package. Ripping those with
one drive is going to slow us down significantly.