Raid 0+1

After reading somewhat about RAID, some things are still unclear. I read that the fastest yet safeset approach (which I am looking fwd to) is to do a RAID 0+1. I plan to buy another WD Raptor for this, however, do I need 1 more or 2 more. Are a total of 3 drives needed for this? or just 2? I have one Raptor now.

My onboard promise controller has instructions incorporated into the ASUS manual, and is not very helpful. I did a search here also but there is so much and its so scattered, I just get more confused reading about it all.

Further, can I after successfully setting up a RAID0+1 then partition it in half, as I often format my main O/S location but like to preserve my mp3’s and documents on a secondary loacation so that I do not have to load eveyrhting back in again. How exactly does this work?

Thanks to anyone who can elaborate and clearly explain this. :wink:

RAID 0+1 requires at least 4 drives (and it goes up in multiples of 4). besides the striping that is done with raid 0, it also uses the redundancy of raid 1, so in effect, u would have two raid 0 arrays, one being the mirror image backup of the other in case the other array fails. the entire four-disk raid 0+1 array would have about the same performance and capacity of a two-disk raid 0 array, but with additional performance overhead as the result of running two additional disks.

$hit, that means I need to buy 3 more? Ummm, ain’t that rich, guess I will have to chance with RAID 0. I know its less safe but honestly, by the time the drive fails there will prob be something better on the market that I and others will want.

What about after setting up a raid, my other question, can I partition? Will it be safe?

Originally posted by xtacydima
I know its less safe but honestly, by the time the drive fails there will prob be something better on the market that I and others will want.

Yeh, propably there will be new hot stuff, but your data will be lost (if you don’t backup regularly). :a

Yea, but what about S.M.A.R.T. wouldn’t that also indicate failure of a drive. I do backup regularly. I guess that is what I will have to go with. Or, maybe I will just keep two different Raptor’s as 2 seperate drives, their specs show they are really really fast even as standalone. I mean, I doubt I will see any improvement aside fromr unning benchmark sin performance.

The Promise site is an excellent source of info. Raid 0+1 is not really that much more stable than RAID-0. In fact the odds of losing an array are greater (cause there are 2 arrays).
With the Raptors, the chances of a drive issue is extremely small, they are built like a you-know-what and failure is VERY rare. you will deffinitely see (feel) more speed with Raptor RAID-0 because you will have the advantage of double the cache and access times. Trust me, it’s FAST. virus scans take 1/2 the time, boot-up is over in a minute, etc, etc.

What controller do you have? I’m guessing it’s a 2 port SATA, so the option of a RAID 0+1 isn’t there anyway (with Raptors).
Raptors are perfect for RAID-0, you’ll love the speed. I would just go with the RAID-0 and install a 120-JB drive or something similar for backup, just image the RAID to the backup drive and you’re protected.

I run a Raptor RAID-0 with a set of 800JB’s in RAID-1 that I use for backups and storage. That makes a pretty safe setup, cause my images are stored on the RAID-1 array. Drive Image runs an image every night on a schedule, works great.

I highly recommend that you disable SMART on any drive, especially on a RAID controller. It slows performance and rarely does anything usefull. Be sure to enable cache in the Promise GUI program. Be aware that using write-back cache is less safe, but will increase small-file speeds up to 10x over write-through cache.

Have fun!

Raid 0+1 is not really that much more stable than RAID-0. In fact the odds of losing an array are greater (cause there are 2 arrays).

the odds of losing a drive in raid 0+1 are no greater than losing a drive in raid 0. u have more drives available to lose, but the probability of an individual drive failing is no greater as a result of running a larger array, and the loss of one drive won’t render the array unusable like it does with raid 0.

that being said, raid 0+1 isn’t really for the average consumer anyway since it’s so costly; it’s for ppl who can’t afford to have any downtime, and even then, there are better raid implementations, such as raid 5. using a raid 0 array and backing that up to a larger drive is a much more cost efficient method if the array is small, like it would be with two raptors.

My controller is onboard the ASUS board. Manual refers to it as a Promise FastTrak 378 and setting up the Array and all is done in a MBFastBuild utility which is done in my ASUS BIOS. I can’t afford any other drives like a 120-JB so I will just have to keep 2 Raptors in and thats all.

Is it ok to partition the ARRAY? Lets say of the 72gigs I want to make a 42gig and a 20gig partition. This way if Windows ever needs to be killed by a full format, I can preserve mp3’s and documents…etc… on the 42gig partition.

Why should I disable SMART, how can it interfere? It doesn’t affect boot time at all, like half a second more to display OK status in POST to show how it’s running.

Also, I have no GUI program so how do I manage cache (you mention write-back cache and through cache), maybe I don’t need to and its somehow on auto?:confused:

I appreciate all the help so far, its great, I just need to know this obviously before my new Raptor comes and I attempt this all in 3 days.

  1. Partitioning will slow the speeds a bit.
  2. SMART is very poorly implemented, can slow speeds by as much as 10% and does almost nothing usefull. (my opinion)
    There is no universal standard for implementing it.
  3. check with Promise, there should be a version of PAM that you can use.
    Not familiar with that controller, how masy SATA and IDE channels?

One set of SATA and one set of PATA. So I can have a total of 4 drives onboard.

Just checked promise site, my controller isnt even listed. Whats PAM short for, I assume its managing software?

here is my MB manal:
http://www.asus.com/pub/ASUS/mb/sock478/P4C800/e1224_p4c800.pdf

PAM = Promise Array Management.
sounds like you have the equivilent of the TX2-plus controller.
2 SATA ports and one IDE port.

Just one version of PAM AFAIK, won’t hurt anything to try it.

So you are saying it wille ither work or not work? I will try calling ASUS about it. What exactly does the PAM GUI look like. Maybe these options will be available in my BIOS after I set up the array. Can you post a screenshot of PAM.

It’s a windows based utility that talks to the controller.
you can download it and the manual at Promise.

Thanks ever so much, just one question. You said:

“Be aware that using write-back cache is less safe, but will increase small-file speeds up to 10x over write-through cache.”

So which do you recommend? Which do you use? Keep in mind I will have only 2 raptors in 1 array.

Write-back cache will result in lost data if you have a crash (BSOD), if the drive is writing when the crash occurs. This is because some data is in cache when the system halts. This may or may not cause a problem depending on what the data is. so if you have a BSOD, there’s maybe a 50/50 chance it’ll create a OS problem or some other lost data. If you are thoroughly backed up at all times, it’s just an inconvenience, but you need to be aware of it.
Write-through cache does not have this problem, but does not give the speed advantage.

hey, rdgrimes, I just realized the SMART check you were referring to is in your PAM options. Mine is in the BIOS and shows the hdd status during POST, and just displays “OK” to show there is no hard drive failure. I don’t think it anyway stays resident in Windows after POST. So I guess it makes no difference if I leave it enabled in BIOS.

The SMART in BIOS usually refers only to IDE drives, not the RAID. Either way, I suggest turning it off for max performance and fewer problems.

OK, I will keep that in mind and disable it. I called ASUS and the tech said “I don’t know” and so Iw as referred to a higher tech, whow ouldn’t ansser the phone and eventually an auto machine came on for me to leave a message. I will try again tomorrow.

If I can use PAM, that would be cool, I will keep this thread posted and update once I find out so any others would know too.

AFAIK, PAM works will all RAID Promise controllers. If it doesn’t, when you install it you will not have access to your controller or arrays via the methods in the PAM manual. It won’t hurt anything, it just won’t work.
One note, be aware that PAM is designed to manage over networks, so you have to install the correct elements for it to work, it’s detailed in the manual.