SABnzbd Forums

Why does verifying take so long? I've a dual core pc, but the verifying often takes quite long. How to speed it up?

Par2 verification is a very complex procedure, and it's I/O bound. That means throwing multiple cores at the problem doesn't help you during the verifying process. So really, the only way to make it faster is to make sure your hard drives are very fast, and make sure you have a fast (but not necessarily multi-core) processor.

inpheaux wrote: Par2 verification is a very complex procedure, and it's I/O bound. That means throwing multiple cores at the problem doesn't help you during the verifying process. So really, the only way to make it faster is to make sure your hard drives are very fast, and make sure you have a fast (but not necessarily multi-core) processor.

2.4 GHz. e6600.

While that's a great processor, Par2 verification is still I/O bound. And even if you have the best fastest hard drive on the planet, it's still really complex math. It's going to be slow.

Release 0.5.0 will have on-the-fly checks.
This means that a flawless download will not need par2-verification afterwards.
On-the-fly is faster because we do the check just before writing a file to disk.

Repairs will take just as long, but there a multi-core system will actually help.

Just a tip if you still have a IDE disk:
Connect you'r dvd drive and ide disk on separate ide cables.

I understand it takes time, but it seems that with later version 0,40 and 0,45 it takes a hell of a lot more time than in previous versions. If I can do it faster using manual PARRING, repairing and unpacking, that's not a good sign.

par2 and unrar are done with third-party utilities that haven't changed much
since SABnzbd started. SABnzbd has very little influence on performance.

If you feel like experimenting, you can replace the par2 and unrar programs
with older or newer versions.
They are located in the win subfolder of the main SABnzbd folder.

I haven't told the whole story, I'm afraid.

Since 0.4.5, SABnzbd uses ionice on Linux systems that have it to run par2 and unrar.
This is done to lower the disk priority of these programs, since they tend to
consume the whole disk channel.
It can be that the nett performance of par2 and unrar is lower now, especially on systems
where disk access is needed by other programs.

You could check by renaming ionice to something else and see if that improves performance.

I think we will make ionice a user option soon.

Hello, I just installed SABnzbd and so far I like it very much, but the verification process is taking too long.

In my limited usage I have found that when a file is downloaded by itself it takes much less time to verify than when it is part of  an nzb containing many files.  For instance:

I dowloaded a single ~700MB file split into 14 RAR files.  It took 4.4s to verify.

On accident I included this same file in a ~5.5G nzb file.  This time it took 205s to verify.

Some other times from the same 5.5G nzb:

A 1.05G file took 324s to verify.
A 625M file took 124s.
A 1.07G file took 245s.
A 450M file took 125s.
etc...


Also, I just downloaded 2 700M files in the same nzb.  It said one file took 222s to verify and the other file was repaired in 10s.  The log file doesn't state the verification time when a file is repaired.

Looks to me like there is something going on that is slowing the verification process.  Maybe I will try just putting one file in each nzb and see how that works.

make sure you don't load the 2 nzb's at the same time.
As from what I understand verifying is at a lower level as downloading , so effort will go to downloading & verifying of the first nzb will be slower till nzb 2 is fully downloaded

Correct me if wrong shypike

On a PC that's a bit slow, downloading will use resources (CPU, hard disk, maybe memory on a low-memory system)
that are needed for verification.
Given that we try to give par2 verification a lower priority, verification will suffer.
The higher the download speed, the more verification will be affected.

There is an option that stops downloading while post-processing is active.
This is especially for resource-restrained systems and in general for people
who prefer post-processing to be done asap.

Sorry to drag up an old post, but I'm having this issue aswell.

For allmost the past two years, I've been using NewsLeecher to download from Usenet. It's a great software, but after stumbling upon SABnzbd+ and it's great RRS-features, and the fact that it's web-based, I switched over in a snap.

However, the par2-checks seems to be waaaaaaay slower then with NewsLeecher - or even using third-party apps like QuickPar.

We're stuck with par2, although we try to optimize its settings.
E.g., by default it runs on low priority, which is not optimal for all systems.

QuickPar is closed source, Windows-only and not usable for embedded use.
We would love to get our hands on the source code, but either the author
has decided to keep it a secret or he has sold it to a commercial developer.

The newsleecher author charges money for a reason, he invests more
time and resources in his product (and maybe wrote his own par2 code
or bought the QuickPar code).

By all means, I'm not complaining (allthough it might seem so).
I'm just wondering if it's supposed to be this slow, or if there are options to improve it?

I see that there's an "Extra PAR2 parameters"-option under Switches. Is there anything I could do there to improve the par2-checks?