On Wed, Sep 16, 2009 at 10:28 AM, Doug Ledford <dledford@xxxxxxxxxx> wrote: > On Sep 16, 2009, at 7:11 AM, Tom Carlson wrote: >> >> Hi, >> >> I've had a slightly bad experience with port multipliers. I have a >> PCI-e x1 JMB362 on the host end and a SiI 3726 connected to it. (I >> think. It's a 1-5 PM). I have 5 disks connected in raid5 and get some >> fairly appalling write speeds, well below what I'd expect even for >> raid5 writes. Reads too are fairly slow... >> >> $ dd if=/dev/zero of=./blah bs=1M count=512 >> 512+0 records in >> 512+0 records out >> 536870912 bytes (537 MB) copied, 47.4814 s, 11.3 MB/s >> >> $ dd if=./bigfile.iso of=/dev/null >> 8474857+0 records in >> 8474857+0 records out >> 4339126272 bytes (4.3 GB) copied, 144.667 s, 30.0 MB/s >> >> Obviously this isn't the most scientific of tests... :-) but it does >> show slowness with this particular combination. >> >> I'm tempted to go buy a SiI 3132 based controller and compare the results. > > > I would, those numbers look *really* bad compared to what they could be. > > -- > > Doug Ledford <dledford@xxxxxxxxxx> > The wiki at <http://ata.wiki.kernel.org/index.php/Hardware,_driver_status#Hardware_support> has at least a couple comments about PMP throughput. If there is not a better place, maybe that wiki could have a PMP section added and slowly start to be a good source of info for building a PMP based solution. Greg -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
