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 - 04:32:22 EEST
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=
>
>
>
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