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. T 2009/9/16 Majed B. <majedb@xxxxxxxxx>: > Regarding payloads, I've recently bought an EVGA motherboard off > newegg for $120 and it supports upping the payload to 4096 bytes. > > Newegg link: http://www.newegg.com/Product/Product.aspx?Item=N82E16813188035 > Manual guide: http://www.evga.com/support/manuals/files/113-YW-E115.pdf > > The motherboard above has 8 SATA ports, built-in VGA (256MB, if you > care), 1x Gbit LAN, 4x RAM DIMMs and a few more options. I use it for > my primary array: 8x1TB disks. > > ASUS gaming motherboards allow changing the payload as well. > > On Wed, Sep 16, 2009 at 4:28 AM, Doug Ledford <dledford@xxxxxxxxxx> wrote: >> On Sep 15, 2009, at 9:01 PM, Majed B. wrote: >>> >>> I think someone mentioned in the mailing list that the Linux kernel >>> does sort commands before sending them to the disks, so if the disk >>> tries to sort, and its algorithm isn't that good, the performance >>> drops and hence disabling them is a good idea. I believe it's also >>> mentioned in here: http://linux-raid.osdl.org/index.php/Performance >> >> >> It depends on the elevator in use. And regardless, I have yet to see a >> raid5 array ever perform better with queueing turned off instead of on. >> Although, in many cases, very large queue depths don't help much. Testing >> I've done showed that only a 4 to 8 queue depth is sufficient to get 95% or >> better of the performance benefit of queueing. >> >> -- >> >> Doug Ledford <dledford@xxxxxxxxxx> >> >> GPG KeyID: CFBFF194 >> http://people.redhat.com/dledford >> >> InfiniBand Specific RPMS >> http://people.redhat.com/dledford/Infiniband >> >> >> >> >> > > > > -- > Majed B. > -- > 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 > -- 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
