Christian Pernegger wrote:
After doing a little research, I see that the original slowest form of PCI
was 32 bit 33MHz, with a bandwidth of ~127MB/s.
That's still the prevalent form, for anything else you need an (older)
server or workstation board. 133MB/s in theory, 80-100MB/s in
practice.
I just looked at a few old machine running here, ASUS P4P800 (P4-2.8
w/HT), P5GD1 (E6600), and A7V8X-X (Duron) boards, all 2-5 years old, and
lspci shows 66MHz devices on the bus of all of then, and the two Intel
ones have 64-bit devices attached.
The most common hardware used the v2.1 spec, which was 64 bit at 66MHz.
I don't think the spec version has anything to do with speed ratings, really.
That was the version which included 66MHz and 64-bit. I believe any
board using 184, 200, or 240 (from memory) RAM is v2.1, and probably
runs a fast bus. Pretty much anything not using PC-100 memory. See
wikipedia or similar about the versions.
I would expect operation at UDMA/66
What's UDMA66 got to do with anything?
Sorry, you said this was a PATA system, I was speculating that your
drives were UDMA/66 or faster. Otherwise the disk may be the issue, not
the bus. Note: may... be.
Final thought, these drives are paired on the master slave of the same
cable, are they? That will cause them to really perform badly.
The cables are master-only, I'm pretty sure the controller doesn't
even do slaves.
Good, drop one possible issue.
To wrap it up
- on a regular 32bit/33Mhz PCI bus md-RAID10 is hurt really badly by
having to transfer data twice in every case.
- the old 3ware 7506-8 doesn't accelerate RAID-10 in any way, even
though it's a hardware RAID controller, possibly because it's more of
an afterthought.
On the 1+0 vs RAID10 debate ... 1+0 = 10 is usually used to mean a
stripe of mirrors, while 0+1 = 01 is a less optimal mirror of stripes.
The md implementation doesn't really do a stacked raid but with n2
layout the data distribution should be identical to 1+0 / 10.
The md raid10,f2 generally has modest write performance, if U is a
single drive speed, write might range between 1.5U to (N-1)/2*U
depending on tuning. Read speed is almost always (N-1)*U, which is great
for many applications. Playing with chunk size, chunk buffers, etc, can
make a large difference in write performance.
--
Bill Davidsen <davidsen@xxxxxxx>
"Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark
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