Hi All Folks,

RAID-0+1 hard disks connection question
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Kindly enlighten me on hard disks connection to a PCI RAID controller card, which has only 2 IDE slots. Shall I connect it in following way

RAID controller card
IDE slot 1 :- Master as stripping (RAID 1) for speed
Slave for mirroring (RAID 0)

IDE slot 2 : - Master as stripping (RAID1) for speed.
Slave for mirroring (RAID 0)

OR can I make the connection in following way applying the IDE slots of motherboard.

RAID controller card
IDE slot 1 :- Master as stripping (RAID 1) for speed

IDE slot 2 : - Master as stripping (RAID1) for speed.

Motherboard
Primary IDE :- Master for mirroring (RAID 0)
Slave for CDWriter

Secondary IDE :- Master for mirroring (RAID 0)
Slave for CDRom

So that each hard disk has its own channel.

RAI-0 offers real time backup and is very convenient. However there is nothing 100% safe. If an additional backup device is required which one will be preferable, tape or CD?

If tape preferred any recommendation on its selection, any pointer?

Thanks in advance.

Stephen Liu

Stephen Liu

Sorry I to answer your questoin with a question, but how do you setup the RAID so the backup HD mirrors, and what is the stripping word you are using. I'm needing to hookup a HD for back, right now I have my Primary HD as master of RAID ide1 and my Secondary HD as master of RAID ide2.

Is there RAID software to start the mirror process or what?

Any answers, or links where I can look would be most appreciated.

Hi guys. Stephen, Do you have the manual that came with the RAID controller card? The RAID setups I have used were unable to implement both RAID 0 and 1 at the same time. (By the way, a minor correction - RAID 0 is striping and RAID 1 is mirroring). For a RAID 0 performance (striped) array, both HD's should be master on each IDE channel of the controller card (or mobo if using onboard RAID). A utility should have been supplied with the controller card (e.g.- Promise Fastrack configuration utility) to configure your array (RAID drivers must also be installed). Basically, a RAID 0 combines 2 HD's into one large disk partition. Striping is fast because 2 hd's share the load of data storage equally. The drawback is that if one drive fails, all data is (usually)lost. It is important to backup data often when striping, as data can most likely only be retrieved from a backup source in the event of hd failure (that is the price for the blistering speed). I personally use a third HD for critical data backup, on one of the mobo IDE channels.
In a mirrored RAID 1 array, data is stored simultaneously on both drives in the array. Install 1 drive on each controller IDE channel as master. A third (and fourth) HD can be connected as slave on RAID controller IDE channel 1 and/or 2, and used as a spare or reserve drive. This drive can be placed into the mirrored array in the event of the failure of either mirrored HD. Your RAID utility should give you the option to rebuild the array using this spare drive, thus maintaining data integrity. This configuration is great for critical data storage, but you use twice the disk space you normally would for a given amount of data due to the mirroring.
As for your second suggestion of a RAID disk setup, I am not aware of any way you can utilize the motherboard IDE channels for your RAID system, unless you have onboard RAID.
I hope I have been of some help in this matter. Best regards.

Hi Ericnord,

The RAID software comes with the hardware, the RAID controller card, in a floppy diskette

Stephen

Hi MrSecret,

Thanks for your response.

Sorry I have no manual in hand.

I am a little bid confused. In my concept RAID-0 is stripping and RAID-1 is mirroring. A guy on another list corrected me saying the other way round, RAID-0 being mirroring and RAID-1 stripping based on my posting as follow :-

-------
RAID is also new me. I am running hardware RAID on a PCI controller

From RAID configuration

Award Software Inc.
Drive Number : 0 Maxtor 6L040J2
Drive Number : 1
Secondry Channel :
Drive Number : 2 Maxtor 6L040J2
Drive Number : 3

Set : 1 Sil Stripped Set 76342MB

Press F1 to delete RAID Set
Press F2 to create RAID Set
Press F3 to create Spare drive
Press F4 to resolve conflict

Press to exit RAID configuration utility

- snip -

----

He said that I am running mirroring. However to the best of my recollection, at time of configuration I selected RAID-0 as stripping. I have no idea why the 2 hard disks became a large hard drive.

Now I have following questions and expected to be advised :

1) Can I add a third hard disk as slave to the IDE slot-1 of the RAID controller card as mirroring? Or I must add 2 slave hard disks simultaneously.

2) After adding the slave hard disk/disks I have to reconfigure RAID utility. Will it erase all partitions affecting the OSs.

Thanks in advance.

Stephen Liu

Stephen,
You can add 1 extra drive to IDE 1 as a backup HD for mirroring with no problem, but only in a RAID 1 mirrored array. It should not affect anything in your RAID 1 array or the OS. The third (slave) drive will only be used in the event of failure of either of the other 2 drives in your RAID array. Your RAID BIOS will alert you to array failure (error). Then you can reconfigure and rebuild the mirrored array with the utility program, still without losing data. I don't believe a spare drive can help with a striped (RAID 0) array unless you are manually backing up data to that drive. If the drive is on one of the RAID controller IDE channels, it may not be accessible from your OS, only through RAID utility as a replacement drive. It just saves you from shutting down the computer and physically changing a drive. This can be important if the computer is a server and must be scheduled for shutdown at a convenient time. Failure of a drive in a striped array usually means all data is lost, because the data is stored across both drives (striped).
If you are shooting for data security, definitely use RAID 1 mirroring with a third HD. It would be best if all 3 HD's were identical. HTH

The question is how many drives are you running in your RAID configuration, and are you looking do do RAID0 or RAID1?

With only 2 drives you're limited to one OR the other, but not both. If you have 4 drives on a HPT370, it is possible to do RAID0+1, creating an RAID0 config with the 2 drives on master, then creating another RAID0 array with the 2 drives jumpered as slaves. Once you have the 2 RAID0 arrays set up, you can then do RAID1 using the two. To avoid problems, I would recommend this ONLY IF YOU HAVE 4 IDENTICAL DRIVES. i.e. not only same manufacturer, but same model and size as well.

If you have the extra money to buy 4 drives to do this, it works fairly well, but then again, if you have that kind of cash to burn and you want real performance and reliability, you're better off investing in an "inexpensive" SCSI RAID controller like the Adaptec 2100S and purchasing a couple of FAST Ultra 160 or Ultra 320 drives.

I moved from IDE RAID to SCSI RAID earlier this year, and have absolutely NO REGRETS.

Fact of the matter is, a single 15,000 RPM Ultra 160 drive (Seagate cheetah) is faster than a couple of ATA100 drives running RAID0.

IMPORTANT:

If you're looking for performance AND mirroring, DO NOT DO IT WITH ONLY 3 DRIVES.

Your RAID array can only work as fast as the drive that is mirroring it, so if you stripe 2 drives then mirror with a third, your performance will be no better than if you were running a single drive!

Hi MrSecre and UTLLAMA,

Lot of thanks for your detail information.

This is an experiment to test RAID 0 and 0+1 in order to grep some knowledge of RAID 0 and 0+1. Test on RAID 0 completed and now I am going to test RAID 0+1.

The 2 hard disks used for this test (RAID 0) is :
ATA133 Maxtor 40G 7,200 rpm

Unforturnately I have only one more hard disk available but from different maker,

ATA100 Seagate 40G 7,200 rpm

For such a reason the idea to add only one hard disk turned up to my mind. If I can't continue this test with only one additional hard disk then I have to consider purchasing another ATA100 Seagate 40G 7,200 rpm (Can it work?) I can't affort to burn more money to get 2 more ATA133 Maxtor 40G 7,200 rpm hard disks for experiment.

What I am most interested to learn is when one of the hard disk on RAID 0 down, can I switch its slave on RAID 1 to replace it and add a blank hard disk to the slave place. The server will continue to run automatically without much setup.

B.Regards
Stephen Liu

Stephen Liu

Are you looking for performance or reliability from your RAID array? While RAID1 is always nice to have, I've never found it worth the cost of the additional drives and storage space. Also, depending on the speed of your processor, you may see a performance decrease with RAID1 due to additional clock cycles going to write to both drives/sets of drives. Most people that I know that utilize RAID1 only do it with SCSI drives, and and then, ONLY in cases where you can afford ZERO downtime. In a home setting, I'm not convinced that it's worth the hassle.

CONFIGURATION:

Go with RAID0 with your two Maxtors and use your Seagate as a backup (non-RAID) In this situation, set and jumper your Maxtors as primary and secondary masters on the RAID controller, put the Seagate as primary master on IDE1, CDRW as secondary master on IDE2 and CDROM as secondary slave on IDE2. Make sure you change the BIOS settings to set your IDE RAID controller as your boot drive.

I forgot to add that with RAID0, if your drive fails, YOU LOSE ALL DATA. (a.k.a. "Broken Stripe") I've been told that in some cases it is possible to recover from, but I don't personally know of anyone who has been successful at a broken stripe recovery.

Hi UTLLAMA,

Thanks for your detail advice.

I am looking for performance. But in case of crash of one hard disk how can I recover the data. For such a reason I add RAID-1 for real time backup otherwise I have to use Tape drive or DVD writer.

RE: your suggestion to add the Seagate as backup (non-RAID)
Could the Seagate perform real time backup or just providing a storage place (as Drive-D) for Data? Will all data be saved automatically to this Drive-D or I have to do it manually.

RE recovery of ˇ°Broken Stripeˇ±
I learnt from another List that it is possible which is performed with the RAID utility. I will try to find out its detail. However it is on RAID 0+1 case. I have no idea whether it also applies to RAID 0 case.

One further question if I scarify performance then I can use RAID 0+1 to do real time backup for reliability

B.Regards
Stephen

Stephen -

If you go with putting the Seagate on IDE1, then you would be running RAID0 with your maxtors with no redundancy to the Seagate. The Seagate, for all intents and purposes, would simply be a "D" drive for manual storage of important documents.

I've heard, in theory, that you can recover from a broken stripe too, but the chances, to my knowledge, are NOT good. (corrupt data, etc) With a RAID0 array, information stored to your drives is split between the two drives. If (or when) a broken stripe occurs, you have two drives with half the information on each. The chances of recombining all your hard drive data with no data corruption is, in my opinion and experience, a long shot. Additionally, with th amount of time that it would take just to try to recover your data, (much less troubleshoot corrupt data problems) you could probably recreate your array, repartition, format and reinstall windows. The biggest P.I.T.A. is manually backing up all your data to your non-RAID drive on a regular basis.

For what you're describing, performance + redundancy, you'd probably be better off purchasing an identical seagate drive, create two RAID0 arrays, then creating a RAID1 array between the two.

Hope this helps.

I forgot to answer your last question...

If you're willing to sacrifice performance for redundancy, then you can simply run RAID1 between the two drives attached to your RAID controller. Identical data is written to both drives, so in case of failure of your primary drive, all the information will be retained on the backup.

Hi UTLLAMA,

Thanks for your further advice.

If I understand correctly I can get an additional Seagate to do realtime backup with following setup:

Maxtor Pri, RAID controller slot-1 (0)
Seagate Slave, RAID controller slot-1 (1)

Maxtor Pri, RAID controller slot-2 (0)
Seagate Slave, RAID controller slot-2 (1)

My questions are:

1)With this setup will computer speed be slow down?

2)If one Maxtor (RAID 0) crashed can I replace it with its Slave? Or replace it with a blank new hard disk and let the RAID utility to repair the broken strips?

3)If one Seagate (RAID 1) crashed will there be an warning indicated? Can I replace it with a blank new hard disk and let the RIAD utility to do the repair job.

Kindly advice.

Thanks in advance.

Stephen

Stephen -

Question #1

Your hard drive access will be faster, but because IDE RAID arrays are dependent upon your CPU, I'd strongly recommend a VERY fast CPU to ensure performance. If you have 2 arrays (one Maxtor array and one Seagate array)the speed of your drives will revert to the speed of the slower of the two arrays. Honestly, I've never tried to run a IDE RAID 0+1 configuration with anything but 4 identical drives, but from my understanding of the configuration, it should work as stated above.

Questions #2 and #3

If one of your drives fails, what you'd need to do is replace the drive, create a replacement array, format that array, then use the utilities to copy your drive information from the good array to the new one. Moving the backup drive will result in another broken stripe (on your backup array), and leave you with NO WAY to recover your data. As far as a warning indicator, I'm not sure, but I would guess that windows would develop SERIOUS problems and/or crash, and when you restart your system, the RAID BIOS would notify you of the problem. I hope this helps!

Hope that helped clear up some questions.

P.S.
My new Seagate cheetahs will be arriving tomorrow, so I get to assemble my NEW SCSI RAID ARRAY!!! EIGHT 10,000 RPM Ultra 160 SCSI drives running RAID0!!! Woohoo!!!

Hi UTLLAMA,

Your response clarify my questions. Lot of thanks for your contiunue support and time spent.

One final question is SCSI array indepent of CPU speed?

Thanks

Stephen

Stephen -

Yes, processing power for striping/mirroring on a SCSI RAID array comes from a processor onboard the SCSI RAID controller. You also have the benefit of additional cache, in my case 128 MB versus the 2-8 MB on a IDE drive. A SCSI array is, (in my opinion anyway) a lot more reliable, which is why most "high end" and enterprise servers use SCSI exclusively. Case in point, my home server has run flawlessly, no crashes, bad drives, data corruption, etc since 1996. Average life of an IDE drive is only about 2 or 3 years. Additionally, SCSI can support up to 15 devices PER CHANNEL, allowing you endless possibilities for expansion. Sone SCSI array cards have up to 4 channels, that's the possibility for 60 hard drives, CDROMs, etc. (IDE allows you one master and one slave per channel, and at MOST, have 4 channels for a total of 8 drives) If you want more info on SCSI, follow this link.

http://www.scsi4me.com/index.php?page=SCSI_FAQ.htm#needscsi

Good luck!

Hi UTLLAMA

Thanks again for your advice and effort.

Bye Bye

B.Regards
Stephen