On 03/01/2011 22:18, Stan Hoeppner wrote:
John Robinson put forth on 1/3/2011 10:00 AM:
On 03/01/2011 06:41, Stan Hoeppner wrote:
[...]
When using PMPs one will always have less theoretical b/w per drive than
what that drive can push on paper with a streaming read. Considering
that over 90% of real world workloads are random IO heavy, not
streaming, it's unlikely you'll ever run out of b/w using a PMP based
setup. I haven't.
That's probably true but I don't like making compromises if I can
possibly avoid it :-)
I doubt my motherboard supports FIS PMPs. It's an Asus P5Q Pro, Intel
P45+ICH10R, and I'm pretty sure the ICH10R doesn't support PMPs even if
the original spec said it would.
I just looked it up, and the ICH10R does _NOT_ support PMP. Neither
does the onboard Silicon Image 5723 chip, which actually connects to the
southbridge via a SATA II port (stupid).
Must be connected to the Marvell 88SE6111's SATA port. Well, the spec
says 88SE6111 but my lspci shows an 88SE6121. The 88SE6121 ought to have
two SATA ports, but I've found odd behaviour with the two non-ICH10R
ports on the board when testing - basically if I use the second port but
not the first port, nothing appears, even with Asus' Drive Xpert
disabled. This is presumably the SilI 5723's contribution, hanging off
the Marvell chip's SATA port, and clearly no use for RAID where a drive
might die but we want to carry on, so I'll be ignoring the on-board
Marvell/SilI stuff.
BTW, the P5Q Pro has 3 PCIe x1 slots and 2 PCIe x16/x8 slots, plus 2 PCI
slots. You told us the only slot you have available is 1 PCIe x16/x8.
What is consuming the 3 PCIe x1 slots? The PCIe x1 slot just North of
the top x16 slot should be free. I'm guessing the other 2 are blocked
by your GPU cooler, correct?
Ah, I'm sorry, no I didn't say I only the PCIe x16/x8 slot available, or
at least that's not what I meant. I do need PCIe because both PCI slots
are taken, but I do have all three PCIe x1 slots and one PCIe x8/x16
slot available. The graphics card is only single thickness and could
indeed be moved.
I know I could easily put two $30 2-port cards in, but for neatness I'd
prefer one card with 4 ports, which is what I started this thread to
look for. One 2-port card and a PMP is a reasonable solution that I
might yet go for.
NB My PCI slots are occupied by a TV tuner card and a SCSI card which
serves my tape library, and in any case I want to avoid the limitation
of the PCI bus which would have half the bandwidth of one PCIe x1 v1
slot even if it wasn't sharing with two other highish-bandwidth devices.
[...]
I recommended the Marvell based card strictly because it does PCIe x1
rev 2 for 500MB/s. I only use the Silicon Image based cards, but I use
more than one if I have more than 4 drives in an array. The cost comes
out the same at $40 as the Marvell card, but the SI route requires 2
PCIe slots, and you only have one.
As noted I do have more PCIe slots, and I've just found a Lycom PE-115
PCIe x1 2-port SATA-III card for Â20, which some third-party sites say
has a Marvell 88SE912x chip, and is PCIe v2.0, so that'd be my
multi-card solution - two of them would give me the 4 ports I need to add.
[...]
Well, you've given us conflicting requirements that are impossible to
meet with any solution:
1. Low cost
2. Full b/w per drive
3. Only one PCIe slot availiable
There is not a solution available to meet all of your criteria.
My own research had got me that far, that's why I was asking here. If
this is unreasonable, please excuse the noise...
Nevertheless, thank you very much for taking the time for such a
considered reply.
You're welcome. I think you're finding yourself in that "I want to have
my cake, but eat it too" situation. You can't get what you want at the
price point you want.
Don't we all want to have our cake and eat it sometimes? ;-)
Thanks again for your thoughts.
Cheers,
John.
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