Dell Optiplex 745 Mini_Tower RAID?

Have a chat with Dell and get them to confirm (or otherwise) whether or not your particular machine has native RAID support. If it doesn't, then any RAID controller vendor should have a list of supported OSes.

For example, Adaptec offer this:

http://www.adaptec.com/en-us/products/series/6e/

... and confirm OS support here:

http://ask.adaptec.com/app/answers/detail/a_id/17115

There are other reputable RAID controller vendors such as LSI, to name just one.

If you not have already RAID features integrated in your system (like in the BIOS), you can of course add a RAID controller in one of the free slots (either PCI or PCIe, depending on what your systems supports). When doing so, i'd suggest do backup your system completely, because most RAID controllers need to initialize a freshly created RAID1, which means, you would loose all your installed data. Best way of doing that is, to make a full system image. Then first install the driver for your RAID controller first (before install it in the computer), and then install the RAID Controller, create your required RAID1, then restore your system image to the new RAID. Your system should boot properly. (in worst case, you have a system image as a backup to fully go back).

Never use those fake-RAID controllers in RAID mode which most desktop boards have included these days. They are terribly unreliable and perform badly.

Rather just add the other disk to the PC, then go into disk-management, and set up your built-in OS RAID 1. That is far more reliable, and the performance is also better, as that RAID can do load balancing, which only some very expensive real hardware RAID controllers can do (and that usually not even as well). Also with OS built-in RAID, you aren't forced to use enterprise class disks, desktop disks will usually work fine too (although enterprise class disks would be better).

The OptiPlex 745MT uses the Q965 ICH8-based chipset, which does NOT support RAID  (RAID requires an ICH8R), so you'll need to add a controller card if you want to use RAID-1.

Be sure you get a bootable card (not all are) if you want to boot the OS from the RAID array.

Note that only the MiniTower version has a full-size PCIe x16 slot, which is the best choice for a RAID adapter card.    The Desktop and SFF units require low profile cards, and the USFF doesn't have this slot.   AND be sure it's not already in use for a graphics card (if you're using onboard video, it will be; but if there's a dedicated video card this slot will already be in use).

If the PCIe x16 slot isn't available, you'll want to use a PCIe x1 card if you have the MiniTower;  otherwise you'll have to use a PCI card adapter (not as good a choice) -- or switch to onboard video and use the PCIe x16 slot.

... since you have Windows 7 Pro you can indeed use the built-in disk mirroring in Windows 7.   You'll need to convert your disk to dynamic, and then you can "add mirror" with the new disk.   It's a bit tricky with the OS partition ... but it does work.

I'd suggest you IMAGE your OS partition before you start, however ... and save the image on another drive (external) -- to be sure you can easily recover if anything goes awry while you're setting it up.

But remind, the built-in Windows RAID mirroring ia a Software RAID, like all the other fake-RAID controllers (they are much worse). It just simulates the RAID1 feature, but has to do that with software, which means, it costs CPU time to calculate, not like a hardware controller, which does that by itself.

You can easily forget about the CPU load, that with today's CPU power is practically nil and therefore in-noticable. It may have been a different story over a decade ago with Pentium III or even lower powered CPU's, but today that is moot.

Well, this is a 3.xGHz Pentium 4.  Whattya think of that?
It appears that the HighPoint RocketRAID 642L will work in the PCI-e 16 slot.
But, it says "PCI-e 2" and would the OptiPlex be compatible?

Just use OS software RAID as I mentioned already. It is much more reliable and performs better. That isn't a real hardware RAID controller, but rather a hardware assisted RAID card, and that is only a little less bad than a pure fake-RAID controller.

Yes, the 642L will work fine.   The PCIe bus is backwards compatible, so a v2 card will work fine in your system.

The HighPoint hardware-assisted cards work very well with Windows, and provide several features you won't get with a simple mirrored dynamic disk configuration (e.g. a software RAID-1 mirror through disk manager) ... most notably online capacity expansion and support for migration to other RAID levels, should your needs ever evolve to that.

Well worth the modest cost of the controller..

What experience is there that the OS RAID is "much more reliable and performs better"?
I remain concerned that this is only a Pentium 4 system and that adding a software load could be inadvisable.

How is it "a little less bad than a pure fake-RAID controller"?
How is it bad at all?

How does that reconcile with "the 642L will work fine"?

I understand hardware vs. software but I don't really understand "pure fake" vs. "less bad".
What does the 642L do?  Not do? in that context?

The difference in short words would be: with the 642L, you can access the RAID only with the driver (you would have to provide that before setup will recognize your drive). The software RAID does not need any driver.

I agree that with RAID-1 there's no performance advantage of using an add-in card ... the key difference is in the management features.    I'm sure rindi's right about the mirrored disks doing load balancing on reads, but I think the RocketRAID does this as well (but don't know that for certain).

As for the reliability with various disks ... high-performance RAID controllers are indeed very sensitive to this -- they'll fail a disk if it takes too long to do a recalibration, so you need disks that use "TLER" (time limited error recovery).   But I don't think an inexpensive hardware-assisted controller has this problem.

Nevertheless, I don't disagree that you can simply use Windows built-in mirroring to do what you've asked here and save the cost of the controller.   A simple disk mirroring operation isn't a stressful CPU activity ... even on the Pentium IV in your system.

r.e. "... The PC of yours normally doesn't have "just a Pentium IV", but rather normally it comes a with Core 2 Duo CPU ..."  ==>  The OptiPlex 745 series shipped with Pentium IV's, Pentium D's, Celeron D's, and Core 2 Duo's  ... so I'm not sure I'd say it "normally comes with the Core 2".      But even with a Pentium IV, it's got plenty of "horsepower" for the software RAID option.

you can check the original shipping spec of your PC with the Dell warranty tool.
This should tell you the CPU that it shipped with.  You'll need the service tag from the outside of the box.
http://www.dell.com/support/home/us/en/04?c=&l=&s=bsd

I'd be a little concerned about putting a critical app on a PC of this age (even with RAID?).  It will almost certainly be out of warranty.  I think they were first launched in 2006?

"... you can check the original shipping spec of your PC with the Dell warranty tool.     This should tell you the CPU that it shipped with."

?? WHY ?? ... the author already knows what the CPU is:  "... Well, this is a 3.xGHz Pentium 4"

Thanks