Question about Raid1

[otherwise]

Hello all. I'm building a computer that's going to store some pretty important data, so in addition to weekly backups I wanted to have two drives in raid 1.

I know how this should work in theory, but I have some questions about how it works in pratice:

1. The first option is hardware raid 1, i.e. using the motherboard controller. If an error is detected, how is it reported?

2. The same question as #1, but this time using dynamic volumes to create the raid 1 partation in windows. If an error is detected, how is it reported?

3. If I want to install Windows 2000/XP/Vista to a software Raid 1 partation, exactly how does this work? I've never seen an option within the windows install to create an dynamic volume on install.

 

[RebateMonger]

Errors with hardware RAID controllers are reported by software created by the RAID chip maker. They can send email warnings, sound audible alarms, or publish error messages in the System Event log.

Windows dynamic disk errors would be found in the System Event log.

I'm not a big fan of Windows Dynamic Disks, although RAID1 is the least risky of the Dynamic Disk options. If you chose that direction, be sure to carefully read Microsoft's available literature on the topic and how to handle troubleshooting and repair issues. Don't wait until AFTER you have a problem. Fortunately, as long as you have backups, it's hard to get into horrible trouble.

You can emulate RAID1 failures using Virtual PC. Install XP or Vista in a Virtual PC window and create a couple of virtual disks, make them dynamic, and play with them. I've done that several times, testing what happens with a dynamic disk failure and how to recover from it.

 

[alaricljs]

PS - Your motherboard does not have hardware raid. It's just software raid in the driver for the drive controller.

 

[erwos]

Originally posted by: alaricljs
PS - Your motherboard does not have hardware raid. It's just software raid in the driver for the drive controller.

The good news is, you don't need hardware RAID for good RAID 1 performance. Doing two writes or reads isn't exactly a CPU-taxing exercise, at least not compared to parity calculations.

 

[Captante]

Originally posted by: erwos

Originally posted by: alaricljs
PS - Your motherboard does not have hardware raid. It's just software raid in the driver for the drive controller.

The good news is, you don't need hardware RAID for good RAID 1 performance. Doing two writes or reads isn't exactly a CPU-taxing exercise, at least not compared to parity calculations.

One thing to keep in mind is that a hardware RAID controller will be a lot more reliable then using the software controller built in on most consumer-level motherboards, plus performance will be slightly better because parity will be handeled by the controller itself.

 

[MerlinRML]

Originally posted by: Captante
One thing to keep in mind is that a hardware RAID controller will be a lot more reliable then using the software controller built in on most consumer-level motherboards, plus performance will be slightly better because parity will be handeled by the controller itself.

Reliability is not guaranteed simply because you buy an add-in RAID controller. Nor is performance guaranteed with having a dedicated RAID processor.

In the case of RAID 1, there is no parity to calculate. Data just gets written twice. There is almost no performance impact on CPU load.

The nicety of buying an add-in RAID controller means that if your motherboard ever fails, the RAID controller can move to any newer motherboard. On the flip side, if the RAID controller fails you may simply buy another or have a spare controller on hand rather than replacing the entire motherboard.

There are some additional features that could be of interest on add-in RAID controllers that are not available on typical on-board implementations.

 

[bryanW1995]

I'm looking to set up raid 1 for my wife. Can I do it without losing the data/os from the original drive?

 

[erwos]

Originally posted by: bryanW1995
I'm looking to set up raid 1 for my wife. Can I do it without losing the data/os from the original drive?

Depends on the implementation. I think some nVidia chipsets can do that. I'd back everything up anyways, though.

 

[bryanW1995]

yeah, we're on a home network. I have already copied everything that is important onto my hd. It is on a cheapie foxcon 939 mobo that I got for $49 last year. I couldn't believe it when I found out that the mobo came with raid at all!

 

[Captante]

Originally posted by: MerlinRML

Originally posted by: Captante
One thing to keep in mind is that a hardware RAID controller will be a lot more reliable then using the software controller built in on most consumer-level motherboards, plus performance will be slightly better because parity will be handeled by the controller itself.

Reliability is not guaranteed simply because you buy an add-in RAID controller. Nor is performance guaranteed with having a dedicated RAID processor.

In the case of RAID 1, there is no parity to calculate. Data just gets written twice. There is almost no performance impact on CPU load.

The nicety of buying an add-in RAID controller means that if your motherboard ever fails, the RAID controller can move to any newer motherboard. On the flip side, if the RAID controller fails you may simply buy another or have a spare controller on hand rather than replacing the entire motherboard.

There are some additional features that could be of interest on add-in RAID controllers that are not available on typical on-board implementations.

Of course theres no guarantee of reliability with any RAID controller & I never implied that there was ... all RAID 1 protects against is mechanical failure of a HD & a virus or other cause of data corruption can still result in the drives contents being rendered useless.

An add-in PCI hardware based RAID controller is however a much more robust solution then software RAID & many of the good ones can be setup to do parity checks as data is being written which serves as a form of error-correction. Another major advantage of an add-in PCI controller is that if the motherboard dies, all you need to worry about is replacing it with the same chipset rather then being tied to the identical board & the same goes for the controller card itself as you said.

RAID 1 isn't worthless in particular for a server or for any computer containing large amounts of important data, but its no substitute to a regular back-up routine using external media like a USB, Firewire or ESATA HD ... in fact given the reliability of modern HD's, if it comes down to one or the other method, effective backup should be implemented before RAID IMO.

 

[alaricljs]

And yes having REAL hardware RAID can improve performance on RAID 1. This is because instead of transmitting the data twice (once to each disk) the data is transmitted once to the hardware RAID controller which then handles transmitting it twice to the 2 drives.

 

[otherwise]

Thanks for the replies so far!

Performance really isn't a concern. The system is being upgraded from a P3 566 MHz that is on its last legs. I don't think the performance difference between Raid 1 solutions is going to make a big difference in perception here!

Now, three more questions:

1. Does anyone have any experience with the "Matrix RAID" that comes with most Intel motherboards? The big question is if I can somehow set this up s.t. there is automatic reporting if it detects an inconsistancy. I've looked through the material on Intel's website but it doesn't even mention how it discovers a drive is inconsistant -- just how to replace and rebuild if one is.

2. Speaking of inconsistancy, how exactly does a raid controller -- software or hardware -- determine which drive is the bad one?

3. Does anyone have some firsthand experience and can reccomend a good 2xSATA addon raid card that gives some benifit, besides performance and the ability to repalce the card easier if it fails, over the intel "Matrix RAID" which comes with most motherboards? Either better reporting or better error detection (someone mentioned verify on write before)? SIIG is the only 2xSATA PCI-E raid card I saw under $100 that didn't get absolutly horrible reviews (adapteic and promise apparently both have some huge issues according to newegg comments) and I'm wondering what you get for the quantum leap in price to the other vendor's 2xSATA PCI-E raid cards.

 

[alaricljs]

ok, 2: Same way a non-RAID controller detects a failure. The drive responds to a write or read operation with a failure code. Or the drive just plain doesn't respond at all. SMART allows you to monitor a drives internal table of self-checking, I use a monitor on Linux, there should be something similar for Windows. The SMART table will contain a whole lot of info including the count of "soft" errors. These are recoverable errors that if they start piling up are a sure sign that the drive is going to be failing soon. Preemptive treatment is the best cure.

My only experience with add-on SATA cards are some PCI-X cards with 4 and 8 ports. I don't use the RAID drivers, so no help there. If you don't tell us who the other vendors are we can't tell you why they're expensive. The cheap cards are software RAID done in the driver. The expensive cards that are hardware RAID aren't usually 2 ports, they're 4 or more. In the slightly more expensive than cheap there's possibly better drivers/features.

edit: Ouch, I just thought about this. I have no idea if RAID drivers do SMART pass-through so that you can monitor the individual drives. I do all my software RAID on linux, so don't have these issues.

 

[Captante]

Originally posted by: otherwise
Thanks for the replies so far!

Performance really isn't a concern. The system is being upgraded from a P3 566 MHz that is on its last legs. I don't think the performance difference between Raid 1 solutions is going to make a big difference in perception here!

Now, three more questions:

1. Does anyone have any experience with the "Matrix RAID" that comes with most Intel motherboards? The big question is if I can somehow set this up s.t. there is automatic reporting if it detects an inconsistancy. I've looked through the material on Intel's website but it doesn't even mention how it discovers a drive is inconsistant -- just how to replace and rebuild if one is.

2. Speaking of inconsistancy, how exactly does a raid controller -- software or hardware -- determine which drive is the bad one?

3. Does anyone have some firsthand experience and can reccomend a good 2xSATA addon raid card that gives some benifit, besides performance and the ability to repalce the card easier if it fails, over the intel "Matrix RAID" which comes with most motherboards? Either better reporting or better error detection (someone mentioned verify on write before)? SIIG is the only 2xSATA PCI-E raid card I saw under $100 that didn't get absolutly horrible reviews (adapteic and promise apparently both have some huge issues according to newegg comments) and I'm wondering what you get for the quantum leap in price to the other vendor's 2xSATA PCI-E raid cards.

At the moment you might be safer getting a standard PCI controller card because they are much more mature products, although the selection is pretty thin for hardware-based models ... this Highpoint card is decent @ $130 + $6 shipping:

HighPoint RocketRaid1742 PCI SATA II Controller Card RAID 0/1/5/10 JBOD - Retail



If you want to go with somthing better then the Highpoint, you'll have to go with PCI-e ... this 3ware card has worked well for me & won't break the bank @ $190 + $6 shipping:

3ware 9650SE-2LP PCI Express Lanes: 1 SATA II Controller Card RAID Levels 0, 1, Single Disk, JBOD - Retail



Anything significantly better then the 3ware will take you to the $300+ price-point & I'd say isn't worth it for your application.

Also don't use the reviews on Newegg as an indicater of quality, most of the people writing the negative reviews don't bother to do their homework before getting started & make bone-head mistakes as a result.

Remember the most important step in creating your RAID array should happen before you even install the card in your system, read the manual (!!!) ... most people don't bother doing this & it's the primary cause of problems.

 

[otherwise]

Is there some advantage to hardware raid besides performance? The things I care most about are notifications and reliability which really don't seem to require a hardware raid solution.

I was thinking about something along the lines of this adaptec card. It might be "software" raid but it uses Adaptec's windows software which includes notification on warnings/errors which is important to me, and since I think I'm going with Vista the fact Adaptic certifies it as Vista compatible is a plus.

 

[otherwise]

Originally posted by: alaricljs
PS - Your motherboard does not have hardware raid. It's just software raid in the driver for the drive controller.

A quick termonology question. What are "hardware independent" RAID solutions like Dynamic Disc Arrays referred to, considering the term "software RAID" is already taken?

 

[alaricljs]

Um, marketing speak for "we have the same thing as everyone else, but we call it something else"

 

[otherwise]

Originally posted by: alaricljs
Um, marketing speak for "we have the same thing as everyone else, but we call it something else"

 

[Captante]

Originally posted by: otherwise
Is there some advantage to hardware raid besides performance? The things I care most about are notifications and reliability which really don't seem to require a hardware raid solution.

I was thinking about something along the lines of this adaptec card. It might be "software" raid but it uses Adaptec's windows software which includes notification on warnings/errors which is important to me, and since I think I'm going with Vista the fact Adaptic certifies it as Vista compatible is a plus.

Yes ... In fact the main advantages to a hardware-based RAID controller are more robust error-correction & higher reliability ... the only major performance advantage it provides is slightly lower CPU overhead & faster re-building of a damaged array.


Most of the lower end Adaptec controllers I've used are re-badged High-Point models (including the 1220sa) and aside from a fancy software interface offer no major advantages over most built-in motherboard based solutions ... if you go that route you would be better off just putting the cost of the controller into a higher quality motherboard instead.

If you want real data security that will provide true redundency for your valuable files, go with the $190 3ware I linked above & install 3rd-party disk monitering software.

 

[otherwise]

Thanks again for your advice Captante. I have one last question for you.

Would this highpoint card be essentially the same as the 1740 you linked? On paper they look the same spec-wise except for the PCI-E interface, and I am going to guess it is a hardware card since there are memory chips on the PCB and writethrough/writeback cache are listed as features. For some reason it's $30 cheaper.


EDIT : Link to the HP2300 spec sheet.