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4 Drive RAID

Posted on 2003-02-26
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Hi,

I want to set up RAID on my computer.  I already have the controller and I have 4 hard drives.  Two of the hard drives are 20GB and 2 of them are 40GB.  I figured I would set up RAID 1 with the 2 20GB's in one array and the 2 40GB's in another array.  Is this my best bet or would something else be better?  Also, how would I install the drives?  Like this?

         IDE1     IDE2
Master   20GB     20GB
Slave    40GB     40GB

Thanks

Greg
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Question by:rinker97
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by:kiranghag
ID: 8027452
ide does not allow u to read from two devices (on a channel) at the same time...
so your setup seems justified in some cases.
if only one mirror is read, ur acceses would be distributed accross the channel, so no problems

but if both the mirrors are accesed at a time..it would load the thing...
neways i dont think of any better configuration in the current setup...u can config as u said...
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by:cuynen
ID: 8027500

you shouldn't create an array with drives of different sizes, so 2x 20 in one array and 2x 40 in another array is the best for you

it's best to divide an array over multiple channels, like you have already done
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by:1175089
ID: 8027565
You can use RAID0+1(10) (mirror +stripping) if your controller support this.
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Author Comment

by:rinker97
ID: 8027653
My controller is the Promise TX2000 and does support RAID 0+1.  Would I gain anything by configuring it this way?  Also, what if the drives were all 40GB.  What would be my best configuration?
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by:rrhunt28
ID: 8028366
Yes if you want to do a 0 + 1, 4 40's would be the best bet.  Two would be for speed two would be for back up.  It all depends on how you plan on using the machine.  Good luck.
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by:cuynen
ID: 8029079

if you're going to do that, I suggest cross-channel stripe sets and then mirroring the masters (first set) to the slaves (second set)
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by:magarity
ID: 8029335
Hi rinker97,
You've written "Is this my best bet or would something else be better?"  But this can't be answered until you let us know what you want from RAID.  Do you seek performance or reliability?  You can't have both.
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by:heskyttberg
ID: 8030201
Hi!

I would suggest you do like this!

Keep the drives as youhave written in question.

Do mirror on the two 20Gb and keep system and important applications and data on thoose.

Do a RAID 0 set of the two 40Gb.
This is for speed.

Don't do 0+1, the ide raid cards aren't really quick enough to handle that.

That way you get an 80Gb drive where you can put games music and such, but remebmer if one of thoose fails all data on them is lost.

As said earlier IDE can only read or write to one device at a time on any one ide channel.

So with only two ide channels on raid card trying to create a raid with more than 2 disks is almost meaningles, you won't gain any extra speed.

For this you need to buy some other promise ide raid card, there are such with up to eight IDE channels only allowing one device/channel.

Hope this helps a little.

Regards
/Hans - Erik Skyttberg

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by:1175089
ID: 8032656
Don't use RAID0 (block striping) /This is not a raid -no redundancy/, if one of your drives crashes, ALL your DATA becomes unavailable.
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by:rinker97
ID: 8033548
You are correct that I didn't say what I was looking for out of my RAID.  Sorry I left this off.  

I plan on installing it on 2 servers at work.  I would like improved performance but I am mainly looking for security.  The reason I had the 20GB and 40GB in my original config was because I was trying to use some of my old drives.  I planned on installing the OS on the 20GB and then use the 40GB for data.  I want them both to be mirrored for redundancy.

I just got the Promise cards so I can return them (well one of them at least since I haven't opened it).  Is there a better controller that I should look at?

Thanks for everyones help.
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Expert Comment

by:jacqadm
ID: 8033594
Raid 0 on 2 disks = 2 * capacity of the 2 disks
                  = no redudancy
                  = fastest read/write

Raid 1 on 2 disks = 1 * capcity of the 2 disks
                  = redudancy
                  = slowest write

anyway, if you use or not use RAID, when you delete a file/directory, it's deleted, ok in the recycle bin
If your controller crash, you should replace the controller.

And Remember IDE RAID is not really RAID as used in server environment, NOT HOT Swappable

So Why using RAID in a desktop ?
You want to kill a fly with a hammer !!!!!!!!!
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by:rrhunt28
ID: 8033865
For what you are doing you want to use raid 1,  true that is not "true" raid because you can not hot swap it, however if it is a small business that can not aford the cost of server's with raid arays, raid 1 is a good alternative.  The bottom line is, if one disk fails, you will still have the info on the other disk.  And I use raid 0 on my desktop for games.  I do not care if a disk goes and I lose information, that is what a cd burner is for.  And, I might be lucky, but I have never had a disk go bad.  
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by:cuynen
ID: 8033961

if you're going to set up RAID-1 at work, you're cheapest solution will be to go for the Promise RAID-5 range

a mirrored stripe array (RAID 0+1) CAN be more efficient (RAID-5 increases both speed and reliability, but still can handle only one request at a time)
but you will need a special (expensive) controller which can distribute read requests across mirrors (with one mirror, two users/requests can be serviced simultaneously)
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by:cuynen
ID: 8033972

to jacgadm:

true, IDE RAID is definitely not as versatile as SCSI RAID
false, e.g. Promise has been rolling out hot swappable IDE RAID solutions for at least two years now
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magarity earned 300 total points
ID: 8034258
The definition of RAID has nothing to do with hot-swappable disks and there are plenty of removable cages on the market for IDE, so the people yammering about those issues can be ignored there.

RAID-1, mirroring, is correct for this situation as you've already determined.

So, the trick is to put a drive on its own channel to get decent performance.  Well don't forget that the motherboard certainly has two IDE channels built in.  You can use these two for software RAID that comes built in to Windows2000.  I assume 2000 but if this is something else, software RAID may or may not be available.  Then put the other two drives on the Promise hardware RAID card.  Now, the trick is to figure out which disks go where.  I suggest that if this is primarily a file server then the OS can go on the motherboard with software RAID while the files go on the hardware RAID.  There is some small overhead associated with software RAID but it is much less than the collisions involved in using two drives per channel off the hardware controller.  Doubtless some of the same people who think RAID requires hot swap cages will scream over the idea of software RAID but I assure you that it is a perfectly acceptable solution in this situation.  The alternative is to spend $400 or more on a quad channel (or more) IDE RAID controller.  If you are trying to re-use old drives then I think being budget-minded is the idea that will carry the day.

If this is an applications server, web server, or other services then the OS should probably be the one on the hardware RAID.  I'm not clear on what the job is of the server in question and this will determine whether storage or OS get the hardware RAID.  Without this info, I won't make a hard recomendation.  Anyway, if the OS goes on the software RAID, reserve some space on the hardware RAID drives for a partition dedicated to the swap file.  Then force it to there via advanced system settings once the OS is installed (assuming Windows).  Swap files are the one no-no of software RAID.

Other issues include the presence of an IDE CDROM drive on one of the motherboard's channels.  Does your server really need a CDROM installed all the time, or just for initial OS installation?  I suspect that once the OS is installed, you won't need it.  You can then remove it because otherwise its presence on the channel will have a significant impact on software RAID performance.  In the rare times in the future when the server might need some software loaded from CDROM, share a CDROM drive on a workstation and install over the LAN.

Of course, if you're willing to return the basic Promise controller for their more expensive four channel model then go right ahead.  They are available from discount mailorder for around $400.  Otherwise having two drives per IDE channel will bog down a server's performance.
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by:CleanupPing
ID: 9569348
rinker97:
This old question needs to be finalized -- accept an answer, split points, or get a refund.  For information on your options, please click here-> http:/help/closing.jsp#1 
EXPERTS:
Post your closing recommendations!  No comment means you don't care.
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by:magarity
ID: 9575228
I prefer my analysis of Date: 02/27/2003 07:24AM PST but then I'm biased.

I do NOT prefer this new EE color scheme of all pale bright blue and pale bright yellow on white.  It may look good on a CRT but it's a blaring headache maker on my laptop's LCD .
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