> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of Doug Ledford > Sent: Wednesday, September 16, 2009 9:28 AM > To: Tom Carlson > Cc: Majed B.; David Rees; Richard Scobie; Greg Freemyer; Drew; Linux RAID > Mailing List > Subject: Re: Port Multipliers > > 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. Um, yeah. No kidding. I did the same tests on a very "low rent" system using a mid-range Asus / AMD 64 x 2 motherboard and a $45 three port Chinese clone SiI 3124 interface card feeding a ten disk RAID6 array: RAID-Server:/RAID/Server-Main/Temp# dd if=/dev/zero of=./blah bs=1M count=512 512+0 records in 512+0 records out 536870912 bytes (537 MB) copied, 16.0076 s, 33.5 MB/s RAID-Server:/RAID/Server-Main/Temp# dd if=Test_HD.TiVo of=/dev/null 3952838+1 records in 3952838+1 records out 2023853135 bytes (2.0 GB) copied, 19.4791 s, 104 MB/s And from cached data: RAID-Server:/RAID/Server-Main/Temp# dd if=./blah of=/dev/null 1048576+0 records in 1048576+0 records out 536870912 bytes (537 MB) copied, 1.51728 s, 354 MB/s Doing ordinary daily rsync backups between two similar systems across a 1000BaseT LAN I regularly hit peaks of 75 MB/s with sustained rates well above 50 MB/s. -- 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
