The 3rd (& more) HDD in a RAID should be...?

[gamefan]

I have two 37GB WD Raptor SATA (version 1 sata) in a RAID0 for primary os. I believe they each have have 8MB cache.

If I were to want not only performance RAID0, as I already have, but adding safety too, with parity or RAID1, what kind of 3rd HDD options do I have?

Q> 3rd HDD specs
Would it need to be the same
make,
model,
interface, (SATA vs SATAII vs UDMA133 vs ATA100vs any other (external))
size GB, Is greater than or equal to ok?
cache MB, Some newer Raptors have 16MB cache

Q>performance loss
Is there any chance that the current performance of the RAID0 I have can be maintained?

Q>
Is there any chance to set this up AFTER the RAID0 os is fully set, up and running?

I am not sure if partity and RAID1 are one and the same. A totally diff from just keeping a backup file, I'm thinking about full time real rime copies of (everything) form main HDD(s).

[MadMan007]

Parity usually refers to RAID 5. It is tolerant of one drive failing and can then be rebuilt. It requires at least 3 drives.

RAID1 is mirroring and basically keeps an identical copy of data on two drives. RAID 10 (also called 1+0) consists of at least 4 drives made up of two RAID 0 arrays which are identical to each other. If one of the RAID 0 arrays fails the other one continues to work and depending upon which drives fail it can be tolerant of two drive failures - if one of the RAID 0 arrays fails entirely the other one will still work. RAID 10 is the type of array needed to keep true RAID0 performance and have redundancy. This type of array isn't possible with 3 drives though.

You can probably find an explanation of RAID types and advantages/disadvantages on wikipedia.

[gamefan]

Then a 4 HDD RAID10 would be my next logical step, assuming no 3 HDD could be fast. What about the req'd specs of the 3rd & 4th HDDs then in a RAID10 wrt themselves and the #1&2 HDDs?

[gamefan]

I just found out the ICH5R can do RAID0 or 1 w/ 2 HDDs, probly why it has a Promise SATA/UDMA133 RAID controller on this gucci mobo too. The ICH 7, 8, 9R can do 4 HDD RAID10 etc.

http://www.intel.com/support/chipsets/imsm/sb/CS-022304.htm
http://support.intel.com/support/chipsets/imsm/sb/CS-026615.htm

[Nebuchadnazzar]

you could get a 80GB harddrive that runs outside of your raid that you backup the Raptor's information to. Find a program that copies or images the data from the raptors to the backup drive every few days. This way you keep your raid 0 performance, there's little risk of screwing up the existing raid and it prevents corrupt data if the raptors develop bad sectors. (assuming the back up hasn't)

[gamefan]

excuse my complete ignorance, oh you said find a program. I haven't been smart in the past wrt safety. I had XP not be able to boot cus I pushed the pw off button in hurry while in sleep. BSOD. O I am exploring my options. I don't know what gets you out of a BSOD situation. If its a point that you need to have a raid array (works full time automatially), a complete copy for xcopy (say from a single 80GB drive done every few days), if the cd(dvd) install disks work, or backup&restore (I don't even know where how big this would go), or if a startup disk(s) works. Once I have a definite hw solution to follow then I need a condensed version safety drill tutorial. Still like to know 3rd and 4th HDD for a raid 10 and the 3&4 HDD specs wrt each other and #1,2 HDDs (now identical). Just to see if thats possible in future.

[Nebuchadnazzar]

You can usually fix boot problems by using the tools on the windows CD, like the recovery console to run chkdsk which can fix filesystem problems, or if windows is really messed up you can do an emergency reinstall but it will reset windows back to defaults but keeps your data.
The only times i get bsod from windows bootup is if i've been screwing around with overclocking too much and i corrupt crucial data, then the only fix is a windows emergency reinstall. I recently tried to resize a partition but it failed and the computer would restart when it tried to load windows (i guess the filesystem became corrupt) but i used the repair console, ran chkdsk and it fixed everything.
If your really in a bind there's Knoppix which is Linux booted from CD which has enough tools to fix anything, even give you access to your data if you need to recover files.

[jt001]

Raid 5 isn't a "constant backup", it's not a backup at all in any sense, it's just there to ensure uptime if one drive fails. If a virus hits, you accidentally delete a file, etc., RAID won't do anything to help you there. User error or file system corruption accounts for about 99% of data loss, RAID won't help you there.

Get an 80GB or larger drive, and set up Windows to do an automated backup every day, problem solved.

[MadMan007]

Ideally the 3rd and 4th drive in a RAID will be identical. If not it depends upon the RAID controller, some will be able to use different drives but you'll still be limited by the smallest ones. For example, a RAID0 array with 2 36GB and 2 74GB drives would be limited to 144GB (36*4) but it does depend upon whether the controller can do that.