[linux-audio-user] Ardour, Jack, and 2.6 kernels + XRuns with the Audiophile 24/96 M-Audio

[Joel White]

Joel White wrote:

> Malcolm Baldridge wrote:
>
>>> I'm using 4 Seagate SX118273LC (18G) drives in a software RAID-1, 
>>> mostly
>>> because I wanted to see what putting together a RAID was like (and 
>>> at the time I bought them, the drives were relatively cheap).
>>>   
>>
>>
>> Bad bad bad bad bad bad bad bad.   RAID1 is good for fault tolerance, 
>> and
>> for read performance... but worse than a single drive's performance for
>> randomised writes.  Software RAID implementations would give you worse
>> performance on writes under all conditions, I wager.
>>  
>>
> Wow, an 8 bad mistake! Actually, I always kinda wondered about that.  
> This could actually explain a lot of my latencytest results: diskread 
> latency performance was fine, but diskwrite and diskcopy was crummy.
>
> Ok, so I dug up an ancient 0.5G Conner IDE drive I had lying around 
> and kludged it in.  Clocks in at a paltry 2MB/s transfer rate with 
> hdparm.  I was able to record 8 channels with Ardour with JACK set at 
> 128 periods with no xrun in sight - yeehaa!  I was about to plan on 
> picking up an IDE/ATA drive tomorrow, but now I have something else to 
> try first.
>
> Thanks, Malcolm.
>
> Joel
>
>> Try a non-RAID volume in your tests.  Keep in mind that one write is
>> triggering TWO writes in TWO transactions over the same SCSI card 
>> (and bus,
>> probably).  This isn't going to be good for latency or bus utilisation.
>>
>> Before you rip out too much hardware (and hair), try it with a "simple"
>> volume first.
>>
>> =MB=
>

Ok, I busted up my RAID and with high hopes fired up jack and ardour on 
a new ext3 filesystem running on a single partition.  Ardour ran for 
about 7 sec and stopped with a 300+ms xrun.  This was running 8 inputs, 
and even running two inputs, things ground to a halt after about a minute.

Just to be sure, I mounted the old Connor IDE and let thing ardour run.  
Got bored by about 3 min and shut it off.  Buying a new drive is looking 
attractive again...

Thanks for the suggestions.  I may still look into reiserfs and the LCK1 
patch set, but I don't have high hopes (a 300+ms xrun?).  I'm thinking 
the aforementioned problems with the Adaptec 2940 is the likely root of 
my troubles.

Joel