Hello, I have just purchased a new computer (Dell) which has a built in LSI RAID controller. I blindly ordered RAID 1 configuration at the time of purchase, and am now trying to understand how it works. I will go step by step, one question at a time. RAID 1 implies mirroring. From what I understand HDD 0 and HDD 1 are mirrors. If one fails the RAID controller will automatically boot from the healthy drive (I tried to unplug the data cable from HDD 0 and yes, it works; the system bios displayed a notice to the effect that there is a problem with the array, but then booted normally from the healthy drive). QUESTION: I played around with the hard drive data connectors and noticed that if I plug the HDD 2 data cable into the mirror drive, the computer does not see it as an independent logical drive, it still sees it as the mirror drive. However, if HDD 0 and 1 are in place, and I put in a 3rd drive plugged to HDD data cable 2, it sees the 3rd drive as an indepandant drive. I can't figure out how the RAID controller decides which ones are the 2 mirror drives and which ones are the indepandant logical drives. What is an array in RAID terms? Thanks very much for your time and help, and cordial regards to all, Augustine
RAID Level 1 Common Name(s): RAID 1; RAID 1 with Duplexing. Technique(s) Used: Mirroring or Duplexing Description: RAID 1 is usually implemented as mirroring; a drive has its data duplicated on two different drives using either a hardware RAID controller or software (generally via the operating system). If either drive fails, the other continues to function as a single drive until the failed drive is replaced. Conceptually simple, RAID 1 is popular for those who require fault tolerance and don't need top-notch read performance. A variant of RAID 1 is duplexing, which duplicates the controller card as well as the drive, providing tolerance against failures of either a drive or a controller. It is much less commonly seen than straight mirroring. RAID Level 1 RAID Level 1 RAID Explained... RAID explained RAID explained
An array is just the collective word for all hard drives in that particular RAID group (be it the drives in the RAID 1 or RAID 5 or RAID 3 arrays). With one of the RAID 1 drives in and the other out, the RAID controller doesn't recognize the content as part of the RAID array. It probably thinks its a new drive that's been hot-swapped in. Also, as RAID arrays are based off the smallest hard disk size in the array, if it were a different size, that could put the halt on the RAID 1 array from attempting to mirror.
Hi, thanks for your notes. It is still not clear. How does RAID pick the 2 drives to mirror; I thought that it would be HDD 0 and 1, and that all others (HDD 2 and 3) were like standalone drives. I am confused by the fact that it I plug HDD1 to the HDD2 data cable, it still functions as a mirror drive. Is it true (as Dell support states) that in order to convert from RAID 1 to non RAID (I made a mistake ordering RAID 1), I must reinstall the operating system, the software, etc (which would be an ENORMOUS pain, considering the amount of software that I have). I just received the computer, and it took me 2 weeks to install all the software. Jean
