quick RAID question

R3N3G4D3 · Post by **R3N3G4D3** » Sat May 26, 2007 7:26 pm

Well, this might seem like a silly question, but I just need to confirm something. I'm planning to build a file server with a raid 5 configuration (since I already had 2 harddrives die on me this year and lost quite a bit of data - both were from 3-6 years ago). As far as I know, software RAID 5 will actually perform faster on any decent (Pentium 3 or newer) CPU than hardware RAID 5 on professional cards such as 3ware, and the only reason hardware raid is preferred is to allow the CPU to perform other tasks (please correct me if I'm wrong). Since I'm planning to build a dedicated file server, this will not be an issue for me. Now I just wanted to confirm that software RAID 5 will work with any motherboard (as long as it can handle at least 3 harddrives), in other words it doesn't need to be one of those newer fancy motherboards that support SATA RAID 0/1/5?

kenc51 · Post by **kenc51** » Sat May 26, 2007 7:47 pm

Software raid is not portable......ie. you can't move the array to another PC.
It has a greater chance of saving corrupt data too.

Hardware raid is faster and you can move the drives and controller to another rig, keep the same array along with your data.
Hardware raid supports other stuff like "staggered spinup", raid migration etc.
Be aware that if your going to run Linux, it doesn't work correctly with software raid, GRUB doesn't know where to install the bootloader without some tweaking and LILO just know (or want to know) about software raid.

R3N3G4D3 · Post by **R3N3G4D3** » Sat May 26, 2007 9:09 pm

Well, then I have a couple more questions. I have heard that Windows 2003 Server is pretty reliable when it comes to software RAID (although maybe not as reliable as hardware), and I have access to it through MSDN Academic Alliance (which surprisingly still works even though I graduated a couple of weeks ago). For a home configuration (not corporate where you need extreme redundancy and superb data protection), would this be a reliable solution?

Now, second question, the motherboards that are labeled as supporting SATA RAID 0/1/5/etc are considered as hardware RAID, correct? Or to have true hardware RAID I would still need to buy one of those 3ware cards?

kenc51 · Post by **kenc51** » Sat May 26, 2007 9:53 pm

Software raid is good enough for most people.......it all depends on how much you care for your data. Hardware raid can send you an automatic e-mail if anything is wrong etc.

No Desktop motherboard has hardware raid, I don't think there's a workstation board that does either.
AFAIK the only way to get hardware raid is by using hardware.....ie. using a 3Dware/AMC, Acera etc. branded card.

liqnit · Post by **liqnit** » Sat May 26, 2007 11:13 pm

So all the boards that have Nvidia & Silicon image or Intel raid chip are considered software raid?

kenc51 · Post by **kenc51** » Sun May 27, 2007 9:25 am

liqnit wrote:So all the boards that have Nvidia & Silicon image or Intel raid chip are considered software raid?

Yep!

liqnit · Post by **liqnit** » Sun May 27, 2007 9:45 am

kenc51 wrote:
liqnit wrote:So all the boards that have Nvidia & Silicon image or Intel raid chip are considered software raid?
Yep!

By taking the risk of sounding stupid i will ask...
but they have a Hardware chip to Handle it all, you config it through the BIOS menu , and you dont need a software installed in orer for it to work.

Why is so diffrent from 3Ware sulutions?

kenc51 · Post by **kenc51** » Sun May 27, 2007 10:48 am

liqnit wrote:
kenc51 wrote:
liqnit wrote:So all the boards that have Nvidia & Silicon image or Intel raid chip are considered software raid?
Yep!
By taking the risk of sounding stupid i will ask...
but they have a Hardware chip to Handle it all, you config it through the BIOS menu , and you dont need a software installed in orer for it to work.

Why is so diffrent from 3Ware sulutions?

There's no such thing as a stupid question here, the stupid person is the one who doesn't ask!

3Ware etc. have an extra "XOR" processor to calculate parity, they also have programmable cache (on-board ram), the bios is on the card (so it's portable), they can support a battery backup in-case of power loss (as data in the cache would be lost otherwise) and they can support other usefull features like raid 6 and as I said already, it's portable.......believe me this can be a god send!

Sure onboard is fine if the rig is going nothing else but acting as a file server, but what happens if after ~3 years the board dies? You then need to replace the board with one that has the same raid controller and possibly even one with the same storage bios version......after 3 yrs this might be hard to find!
If you do go with onboard raid, make sure the rig isn't heavily overclocked as it can cause data corruption, and try not to use that rig for gaming etc. Chances are things will be fine though, plus a good hardware raid card costs ~$250 and more.

R3N3G4D3 · Post by **R3N3G4D3** » Sun May 27, 2007 4:59 pm

So if I understand correctly, there are 2 ways of implementing software RAID, one is by using one of the new SATA motherboards with southbridge that supports SATA RAID so that the operating system isn't aware of it, and another is by emulating RAID through the operating system itself?

Also, I noticed that none of the desktop motherboard support more than 6 SATA drives for a RAID 5 configuration. However, I found several that have 8 or even 10 SATA ports (although only 6 of them work with RAID 5). So if I were to emulate RAID 5 through the operating system instead of the BIOS, would I be able to expand my RAID 5 functionality to those extra SATA drives to put more than 6 drives in my RAID 5 configuration?

liqnit · Post by **liqnit** » Sun May 27, 2007 10:34 pm

kenc51 wrote:
liqnit wrote:
kenc51 wrote: Yep!
By taking the risk of sounding stupid i will ask...
but they have a Hardware chip to Handle it all, you config it through the BIOS menu , and you dont need a software installed in orer for it to work.

Why is so diffrent from 3Ware sulutions?
There's no such thing as a stupid question here, the stupid person is the one who doesn't ask!

3Ware etc. have an extra "XOR" processor to calculate parity, they also have programmable cache (on-board ram), the bios is on the card (so it's portable), they can support a battery backup in-case of power loss (as data in the cache would be lost otherwise) and they can support other usefull features like raid 6 and as I said already, it's portable.......believe me this can be a god send!

Sure onboard is fine if the rig is going nothing else but acting as a file server, but what happens if after ~3 years the board dies? You then need to replace the board with one that has the same raid controller and possibly even one with the same storage bios version......after 3 yrs this might be hard to find!
If you do go with onboard raid, make sure the rig isn't heavily overclocked as it can cause data corruption, and try not to use that rig for gaming etc. Chances are things will be fine though, plus a good hardware raid card costs ~$250 and more.

thanks for the info
i wasnt aware of that problem i have a server with 2 * RAID0 (4*250GB) and never thought about what could happen when it dies.

so the only way is to make backup of the DATA the OS will have to be reinstalled?