Installing on RAID 0

[kseise]

First, I like linux Mint. I am running it on three out of four computers right now. My problem is that my desktop has two SATA drives which I want to use as RAID 0. The only installer I can find that supports RAID 0 is the Ubuntu Alternate installer. Can someone tell me how to do a RAID install from Mint?

[Husse]

I wrote an answer to you - but it seems to have disappeared in Cyberspace....
Probably forgot to Submit
The basics
I don't recommend RAID 0 - to risky
RAID in Ubuntu and it's derivatives is crappy
dmraid is probably what you want
http://packages.ubuntu.com/gutsy/debian ... id?lang=en

[Fred]

I hardily support and second Husse's post. "dmraid" is the next best thing to true hardware raid. Don't be confused by the fake raid that has become quite popular on mobos. It runs a poor third or fourth in performance and reliability.

Fred

[kseise]

Thanks for the replies. I will check out dmraid. It is frustrating to know that I can't get max performance out of this thing. Mint works great on my other machines. It is just the main desktop that has untapped potential. thanks for the help.

[Husse]

@ Fred
Do you happen to know how mdraid fits in - I've not really found out what to think about it

[Fred]

Husse,

"dmraid" is basically a set of drivers for Linux that can enable the use of the fake raid on mobos. The code is higher quality than what Windows uses in the on board firmware. So i tends to be faster and more reliable than the same setup would be in Windows.

It is particularly difficult to install on Ubuntu and derivatives. Mainly because the installer is so automated and doesn't allow for selecting and configuring software before the actual install. It is a chicken and the egg kind of thing. "dmraid" needs to be configured before the install, but you can't download and install "dmraid" until after the system is installed. Here is a situation where Gentoo shines, since it installs manually and piecemeal anyway. Below is a how-to that demonstrates my point.

http://bbossola.wordpress.com/2008/03/0 ... -fakeraid/

"dmraid" is software raid, like fake Windows raid. Software raid in general is a mixed bag. It uses lots of cpu cycles so unless you have lots of cpu power to spare you can actually slow your overall system down rather than gain any speed. As you can see I am not a strong believer in software raid, of any kind.

True, good quality, hardware raid can indeed boost through-put. It isn't cheap, but at least it does work as advertised.

Hope this was helpful.

Fred

[Husse]

@ Fred
You probably helped the other guys in the topic - not me, but thanks anyway
I was asking about mdraid - it's confusing with both dm and md raid

[Fred]

lol... I am sorry Husse. What I read and what I thought I read were two different things.

"mdraid is the traditional Linux software raid. It isn't dependent on any outside support from the mobo. It is implemented and managed completely in the linux software. I have never tried to use it on a dual boot Linux system but I would think it would be problematic. Dual booting with Windows would be out of the question.

"mdraid" is a complete software raid system. "dmraid" allows Linux to use the same fake raid Windows is using on the mobo. You can't dual boot Windows with "mdraid," but you can with "dmraid."

Trying again.

Fred

[Husse]

Thanks Fred - I found info on dmraid simple enough, but mdraid was harder.
I don't use RAID any more as I don't get real hardware raid anyway (on a consumer mobo)

[xwin78]

I think there is a bit of misunderstanding about the nature of embedded RAID Controllers. The only difference between say a Rocket Raid pci card and a a motherboard w/Intel ICH8 Raid is that Rocket Raid handles all the Raid mapping and calculating where as the embedded ICHR8 south bridge controller and CPU share the processing task. There is no need for OS based software to set up or run this type of RAID. Even with the shared processing this method is 90-95 percent faster (RAID 0) than a single SATA drive. The only "FAKE" part of this raid configuration is that the Raid Controller (Intel ICH8 Southbride) does not control all the processing. This is not the same as a true software RAID (ALL CPU CONTROLLED) or a software assisted hardware RAID (OS based software + CPU + RAID Access Hardware).

Husse,

"dmraid" is basically a set of drivers for Linux that can enable the use of the fake raid on mobos. The code is higher quality than what Windows uses in the on board firmware. So i tends to be faster and more reliable than the same setup would be in Windows.

Fred

If this is true ( I am laying a foundation not questioning your knowledge ) then fake raid w/ dmraid under linux should be even better than fake raid under widows. I have set up many windows systems w/ CPU assisted hardware RAID a.k.a "fake raid". I have NEVER encountered data loss of any kind, only dramatically increased thoughput and system speed.

I switched to Linux Mint for many reasons, not least of which is that it is much smarter than windows. "fake Raid" is the only lagging area. This needs to change. Even though dedicated hardware RAID is the best option, CPU assisted hardware RAID A.K.A. "FAKE RAID" is a viable option and it would be just like MINT to have "out of the box support" for this. I do not know if it is possible to create an alternate install cd that can detect CPU assisted hardware RAID controllers during install (like windows).

There are virtually NO decent motherboards w/O CPU assited hardware RAID support built in. To under utilize hardware seems so "un-Linux-like" and defiantly not Minty. If dmraid is truly better that Windows CPU assisted hardware Raid (which is very good) then it would be terrible skip out on supporting this option.

I absolutely LOVE Linux Mint, it's philosophy, cutting edge, hi quality approach this forum, WIKI and every one who is associated with this project. You all ROCK!

I will do what ever I can to help make proper support for embedded RAID a reality. Just let me know what I can do.

[Fred]

xwin78,

RAID, as applies to consumer RAID anyway, has always been a bit controversial. If you Google about a bit, you will find everything from scholarly works to outright flame wars. lol

Personally, I am not a big fan of software RAID of any kind. An explanation is probably in order. A true Hardware RAID array, I am defining as a storage system that is seen as a black box by the operating system. It provides its' own processor, catching, disk syncing, etc. It accepts data at buss speed and gives back data at that speed. It represents no additional cpu load or memory catching load to the host system.

Anything less is some form of software or fake RAID. Anything from slightly assisted to completely implemented in user software.

I would willingly defer to your greater knowledge of how fake RAID is implemented in Windows. Since Windows is proprietary, I am not sure anybody outside Microsoft really knows exactly how it is being done. My knowledge in this area is severely limited for sure.

Having said that, I do know there is program code in non-volatile memory, firm ware, that must be run by the Windows kernel on the cpu to help implement the RAID. Most of these RAID systems also use at least some main memory for catching purposes too. This same scenario exists for any other OS also. The hardware just isn't there to do a complete implementation without main system help.

As I have mentioned before, if you have plenty of spare cpu cycles and lots of memory to work with, you can indeed get some improvement in overall system speed. If you aren't careful though, you can wind up fooling yourself. Remember, a chain is only as strong as its' weakest link. If you are looking at disk through put on an otherwise unloaded Windows system, which is the way most of these benchmarks are done, you will indeed see a tremendous improvement. If on the other hand you load the system up with running processes, as it would be in a normal use situation, you may still see some improvement in disk through put but you will be slowing everything else down to get it. You can see the same phenomena on other OSs to one extent or another too.

Linux's memory and cpu task management, especially in the later kernels is, with out doubt, better than Windows. I have no empirical data to back this up, but I suspect that in most cases, a reasonable fast SATA drive that is properly optimized with hdparm would make for a system that is just as fast if not faster over a wide rage of loads than any of the fake RAID setups. The complexity of a system without fake RAID is also reduced, which almost always translates to, more robust and reliable over time.

Below is a Link that will probably either give you more info. than you really wanted, or link you to same.

http://linuxmafia.com/faq/Hardware/sata.html

Fred

[Fred]

xwin78,

A couple of things I should have mentioned and didn't. To implement "dmraid" would require some major changes to the installer. Actually, It would probably be easier to write a completely different installer for a "dmraid" RAID install. As I pointed out in an earlier post, the highly automated installer used by Mint doesn't lend itself to the kind of install "dmraid" would require.

You do have a point about having it however. It would be a good differentiator for Mint. If you have the skills and time available to help implement it you might consider PMing Clem. I suspect if enough people were interested in implementing it he would consider including it in a future release.

As for my part, I am pretty conservative. Some would say too conservative. The terms "slow" and "plodding" even come to mind. I would have to continue to advise against using it for most users, unless I saw an awful lot of evidence that I was in fact incorrect in my analysis.

Fred

[Husse]

I had a small mail order outlet for computer hardware between 1998 and 2005 so I can say that a know a bit. I only used Windows at that time and for some time I actually ran my business system on RAID 0 (crazy I know - but I backed up several times a day generally 5 times)
Measured in synthetic tests (I would call it "fake tests") the speed gain was amazing - in practical work it was not noticeable, and I did some database work...
I also later found out that the newer fake raids (like some Intel and nforce 4) are useless. You can't rebuild a RAID 1 from the remaining hard disk after a crash - all data will be lost!
You have to buy two new disks, build the array and copy the old one onto the array - stupid
I almost lost a considerable sum of money on that - luckily there were other errors so I could return the mobos and be refunded
But - yes a simple way to get a working raid would be nice, as there is a demand for it

[Fred]

I took the liberty of looking up a couple prices on reasonable quality, entry level, true hardware RAID control cards. They will both handle up to 4 drives.

3ware 9650SE-4LPML PCI Express 4 Lanes: 4 SATA II Controller Card RAID Levels 0, 1, 5, 10, Single Disk, JBOD
US $319.00 ....... New Egg

The Adaptec 2420SA is a 4 port, half size SATA II Raid card, PCI-X with RAID 0, 1, 1E, 5, 5EE, 6, 10, JBOD.
US $325.00 ....... OfficeMax

This is about the least I would buy for reasonable speed, reliability, and fault/failure recovery capability.

Does this give you some feel for what might be missing from consumer mobo "fake/software" RAID set-ups?

Fred

[rec9140]

This is a very, umm, well, umm, topic of high interest for me.

I don't want to get into the whole discussion/argument on what is RAID and is not RAID et al...

I understand the points and perspective of some posts, which I agree with some of the points, and disagree with some of the other points.

So lets just agree that while on board RAID may not meet some needs or be the best RAID, it does work and works quite reliably I've done it for several machines like a library with out issue.

I personally need to get the RAID controllers in a KT7RAID to be able to boot from either just an HD plugged into the controller not even part of a RAID array to be able to boot from it. Tried already, grub dies. You can see the other post on this site.

I am willing to be a tester for any version which supports the HPT370 on my KT7R and the nVidia RAID options via dmraid.

I am in the process of possibly using:

ASUS M2N http://www.newegg.com/product/product.a ... 6813131246 for a new PC, I may or may not use the RAID options, but I need the ports for HD's to boot from so I can put optical drives on the PATA ports.

So I am with xwin78 and lets just drop the whole RAID type issues, and get the support for it into LM KDE and make it that much better and easier for others to transition to a better OS.

[Fred]

rec9140,

I am sorry you mistaken my posts as argumentative. They weren't intended that way. This was, to me anyway, just an exchange of information.

For my part, I tried to state the facts as I knew them and label any opinions that I had as such. There was no argument intended.

I agree that it would be a good differentiator for Mint because there is a demand for it. But I still wouldn't recommend using it in most cases for the reasons I gave in my posts. My experiences with it just don't support its' use.

Fred

[rec9140]

I am sorry you mistaken my posts as argumentative. They weren't intended that way. This was, to me anyway, just an exchange of information.

For my part, I tried to state the facts as I knew them and label any opinions that I had as such. There was no argument intended.

Lets just say that a combo of the term "fakeraid" and some other things, just pushes my button(s)....I don't see it as "fakeraid." I understand that maybe its not as 100% hardware as some other RAID systems, but these are separate controllers on these boards. Another post summed up my point much better than I would.

I don't want to go down this path to far, except to re-iterate what I said that I agree with some, disagree with some points.

Below is the goal I am looking to achieve.....which should be the goal of Linux in general period. Hardware x exists then if it can be reasonably added to linux, great, but to just cut our noses off for spite is just not good for Linux Mint or Linux in general. This seems to permeate thru various Linux things....

I agree that it would be a good differentiator for Mint because there is a demand for it. But I still wouldn't recommend using it in most cases for the reasons I gave in my posts. My experiences with it just don't support its' use.

Theres been at least 3 posts since mine on it, and I think it would be a big plus and fits into Mints "it works/its in there" approach.

So I am offering up to be a tester. I willing to shove hardware at things to test.... I don't code any more, unelss you can write dmraid stuff in SQL

[Fred]

rec9140,

I did a quick Google of "fakeraid" and got over 43,000 hits on that spelling alone, so it is in pretty general use. I define "fakeraid" as any raid that isn't 100% hardware, including the use of "dmraid" on Linux.

I apologize if the term was offensive to you. It never occurred to me that it would be offensive to some. It was used to distinguish if from true, traditional, hardware RAID controllers.

On the general usefulness of whatever kind of RAID you wish to call what is on most consumer mobos, we will just have to agree to disagree.

Fred

EDIT: You should probably PM Clem and offer your services to help with implementation in whatever way you can, and is needed. If enough people express an interest and are willing to contribute, maybe it will come to pass.

[xwin78]

@ Fred

thanks for looking up a few TRUE HARDWARE RAID cards. I have been testing other Distros ( RHL, FEDORA, CENTOS & open SUSE) to get a feel for DMRAID. I have no idea how the "BIG GUNS" get it done, but compared to the "book" of instructions that it takes to get a DMRAID working on Debian---I have a whole lot of respect for the above mentioned. I know they are RPM distros but there has got to be a way to make this happen. I would spend many long nights if I have even one clue where to get started.

Sorry to beat a dead horse, there just has to be a way to get this into the BEST DISTRO--LINUX MINT!

[Fred]

xwin78,

I understand you sentiments. If I could help you without investing the next year of my life in the process, I would. To be honest, I don't do much coding, either c or scripting, anymore. Those days are over for me.

I haven't really looked into it, but my first thoughts are that it would probably be easier to rewrite the installer to be able to set it up from the get go. Installing it on an existing system looks like an exception ridden night mare.

My advice would be the same I gave the other poster. PM Clem and offer your services. I suspect if enough people did this and somebody knowledgeable was willing to head up the project, he might sanction it.

Fred