Re: P5DL2 + Raid-5

In article <drarv6$56k$02$1@xxxxxxxxxxxxxxxxx>, "Martin Weil"
<Email@xxxxxxxxxxxxx> wrote:

> Ok, I think I'll go with the "LSI Logic MegaRAID SATA-150".
>
> Is there a good MoBo (maybe Asus) on the market with a PCI-X slot for that
> controller?

The only higher performance PCI slot Southbridge I know of,
is the 6300ESB Intel Southbridge. It is only 66MHz, but may
be sufficient for a RAID card. Using a search engine may turn
up some older boards with that chip. Using one of those 6300ESB
based motherboards, will likely be cheaper than the following.

The Asus P5WDG2-WS is a "workstation" board with an Intel
6702PXH PCI Express to PCI-X bridge. It should appear for sale
within the next month, and looks like it is in Japan now.
Anandtech reviewed it, but the initial article said they had
problems trying to review the PCI-X. Those comments seem to have
been removed from the article. I would wait until some other
review sites have had a chance to review the operation of the
PCI-X slots, unless you want to be a beta tester.

Asus P5WDG2-WS review
http://www.anandtech.com/showdoc.aspx?i=2631&p=1

Intel 6702PXH 64-bit PCI Hub Data***
http://www.intel.com/design/chipsets/datashts/30363301.pdf

"For conventional PCI Mode, the Intel 6702PXH 64-bit PCI
Hub supports PCI bus frequencies of 33 MHz and 66 MHz.
For the PCI-X Mode 1, the Intel 6702PXH 64-bit PCI Hub
supports PCI bus frequencies of 66 MHz, 100 MHz, and 133 MHz."

The manual was put on the support server Jan 20 or so. The
board is still not listed on the product page that I can see.

http://dlsvr01.asus.com/pub/ASUS/mb/socket775/P5WDG2-WS/e2374_p5wdg2-ws.pdf

Note that the slot placement on a lot of these new boards,
with a mix of PCI, PCI-X, PCI Express, do not allow all
slots to be used at the same time. If you wanted to run
a Crossfire video setup on the P5WDG2-WS, using some dual
slot width video cards, one of the PCI-X slots could be
blocked. So you should examine slot placement in the manual,
to see whether the combination of cards you want to use
will fit or not.

Personally, I would buy 4x250GB disk, and run RAID10
(RAID 0+1) on the Southbridge. That gives a redundant
500GB array. Or, you can also buy the new Seagate 500GB
SATA drives, and just use two of them in RAID1 to get a
redundant array and an easy setup. The reason I recommend
RAID 0+1, is high performance, and equal read and write
speeds. RAID5 has poor write performance, and buying
a RAID5 card with cache and XOR engine, helps to offload
the processor and improve the write performance.

Also, an occasionally asked question posted here is,
"I have a RAID xxx and I want to migrate to RAID yyy -
can I do it on-line ?". You should consider this question
in advance, and research the RAID controller card thoroughly,
to see in fact that it does support migration to a
different kind of RAID array, and that in fact the feature
works. The forums of storagereview.com or forums.2cpu.com
are potential places to look for information on building
big RAID arrays. While some RAID controller cards do have
a migration feature, in some cases it doesn't work properly,
or takes the RAID card designers months to fix.

In any case, a redundant array does not eliminate the need
for a backup plan. You should also plan space on your new
computer, to connect the backup disks. The backup disks
should be unplugged when not in use. (The scenario I would
worry about, is the power supply raises its +12V output,
and burns all the hard disk controller boards at the same
time. No matter what form of redundant array you construct,
it can be destroyed by a power supply failure.)

Paul
.

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