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
