Repair Degraded Raid 5 w/ mdadm

**zackiv31** · November 9th, 2009

It kinda leaves me to believe that something is wrong with my machine... My 10k Raid 0 is only getting 112MB/sec... but then again, I thought I remember benchmarks for my setup at around that level. In Raid5, shouldn't performance be lower then that of a single drive? (Do you have different performance on a single drive?)

**fjgaude** · November 9th, 2009

Well, my single-drive performance is 70 MB/sec read. With raid5 you should get read speed of three drives combined in your case. Remember raid5 is similar to raid0, with stripping, but has the extra overhead of parity calucations. But with fast, fast CPUs these days that extra overhead doesn't hurt anything. So with four of my drives I should get 210 MB/sec, and I'm close.

What might be an issue is the SATA drive controller bus. If it is just PCI then that's your answer. I have PCI-E. The former is only good for about 120 MB/sec; the latter, 500.

**zackiv31** · November 9th, 2009

You might be on to something there... although I'll probably have to look at the specs for the chipset, because the specs for my motherboard aren't revealing much (beyond that I have PCI express and regular PCI)

http://www.pcper.com/article.php?aid=98&type=expert

Might be time for an upgrade afterall...

EDIT: Might be some confirmation here:

http://www.tomshardware.com/forum/169596-28-sata-sata

Look at page 28 where it details what SATA chip this board uses.
"As a manufacturing option, the board provides a Silicon Image Sil 3114 Serial ATA (SATA)
controller and four connectors (that support one device per connector) for SATA devices. These connectors are in addition to the four SATA connectors of the ICH7-R/ICH7-DH SATA interface.
The Sil 3114 controller uses the PCI bus for data transfer and provides a maximum data transfer rate of up to 1.5 Gbits/sec."

EDIT2: Chipset info:

http://www.siliconimage.com/iplicens...ct.aspx?pid=28

That seems like you're correct?

**fjgaude** · November 9th, 2009

Yep. So now what?

**zackiv31** · November 9th, 2009

I buy a new machine? lol... Kinda disappointed in the speed on them, but I'm mostly working with a NAS that tops out at 30MB/sec so I think I'll be keeping this machine for now. I could shell out ~$100 for a "real" PCI E card (even for my main OS which would probably speed it up 2fold), but at that point I should just shell out for a new motherboard/processor/memory.

I don't *need* your types of speeds, but down the line I know I'll be upgrading to a monster machine at some point... just not right now... I spent a good chunk of change on this machine 4 years ago, its approaching its end of life...