Subject: Re: [linux-audio-user] Ardour, Jack, and 2.6 kernels + XRuns with the Audiophile 24/96 M-Audio
From: Joel White (cv223_AT_comcast.net)
Date: Wed Jun 02 2004 - 06:51:04 EEST
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
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