On Thu, Jan 27, 2011 at 5:22 PM, Mark Lord <kernel@xxxxxxxxxxxx> wrote: > But I just don't know. My working theory, likely entirely wrong, > is that if I have N streams active, odds are that each of those > streams might get assigned to different AGs, given sufficient AGs >= N. > > Since the box often has 3-7 recording streams active, > I'm trying it out with 8 AGs now. As suggested before - why are you messing with AGs instead of allocsize? I suspect that with the default configuration, XFS was trying to maximize throughput by reducing seeks with multiple processes writing streams. But now, you're telling XFS that it's OK to write in up to 8 different locations on the disk without worrying about seek performance. I think this is likely to result in overall worse performance at the worst time - under write load. If you are trying to optimize single thread read performance by minimizing file fragments, why don't you simply figure out at what point increasing allocsize stops increasing read performance? I suspect that the the defaults do good job because even if your file are fragmented in 64MB chunks because you have multiple streams writing, those chunks are very likely to be very close together so there isn't much of a seek penalty. -Dave _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
