Slow Transfer at ~15MB/sec

[CrazyJAT]

I have done some testing and found that with each of my 3 1.5 TB hard drives individually formatted as UFS by FreeNAS, I get about 71.5 MB/sec write to each drive. When I create a ZFS Raid-Z partition with all 3 1.5 TB drives, I only get about 15 MB/sec write to the drives.

To test I am using dd if=/dev/zero of=file.tmp bs=1024k count=1024

Why would each drive perform well on its own and not in the Raid-Z? Is it a problem with my raid card?

 

[ProtoSD]

With UFS there's no parity calculation like there is with ZFS. Also you didn't mention what the rest of your hardware was, but ZFS needs more RAM, so that could be part of the problem along with the type of processor you're using. Those 2 things will make a big difference when using ZFS.

 

[CrazyJAT]

It looks like the issue is my controller card. I wanted to reuse an old Pentium 4 system as a NAS, but the board I was using doesn't have onboard sata. I didn't want to invest a lot of money in this project, so I bought a cheap $30 sata II pci card. I recently came into a new board that has onboard sata. Both systems are running the same Pentium 4 cpu and 512 MB of ram. Using this new board I tried my freenas install with my ZFS Raid-Z setup and got about 75 MB/sec from the onboard controller. Then just to be sure, I popped in my sata II pci card and got about 15 MB/sec with the same ZFS Raid-Z. Again I deleted the Raid-Z and formatted each drive as UFS on both systems and both got about 70 MB/sec - 80 MB/sec.

It seems that PCI sata cards, at least cheap ones, just can't perform using a Raid-Z setup. For anyone who is interested, the card in question is a Rosewill RC-217 http://www.newegg.com/Product/Product.aspx?Item=N82E16816132017.

 

[ProtoSD]

It seems that PCI sata cards, at least cheap ones, just can't perform using a Raid-Z setup.

Both systems are running the same Pentium 4 cpu and 512 MB of ram

I'm surprised you're able to load FreeNAS with that little RAM. The controller definitely looks like it was an issue, but even with that, with further testing you would have run into other problems. Anyway, glad to hear you got it figured out and can move on. Get some more RAM ;-)