- Joined
- Aug 23, 2003
- Location
- behind the wheel
the only point for raid 1 (mirroring) is not performance, but security.
if one drive fails, and the other drive is still alive, then you still have your data.
mirroring really does do what the name suggests. it just writes the system data twice, once on each disk, at the same time, so that if you removed one disk from the array, you could just run it off an IDE controller, and never know it was on a RAID controller.
and in raid 1 (mirroring), if you use 2 disks of equal size, say 120GB each, you'll only see 120GB of available space under windows. This is half of the total capacity of the 2 drives.
in raid 0 (striping), you can use 2 disks or more. You nearly double your transfer rate with 2 disks, and increase it even more with more disks, but the gains diminish the more disks you add. You still keep the total capacity of the drives, so 2x 120GB in striping is 240GB. but, if one drive fails, you loose ALL the data.
raid level 5 offers security and speed, but requires several disks. with severall disks, it basically stripes the system data + parity data to all the drives, and if one drive fails, the data on that drive can be rebuilt from the parity data from all the other drives. Losing 2 disks at the same time leads to the loss of all data. The available space is equal to (number of drives - 1) x size of smallest disk. You need at least 3 drives for this setup.
another possibility is level 1+0, basically a mirror array made up of 2 striped arrays. You need at least 4 drives for this kind of setup. Your storage capacity will be half of the total capacity of all your drives--------------------------------------------------------------------------
with your controller, you wrote that you have the options of 0, 1, or 0+1, so if you only have 2 disks of 120GB, then the only options are level 0 for speed (with capacity of 240GB), or level 1 for security (with capacity of 120GB).
If you want to use 0+1, you'll need to get 2 more drives, so you have 4 in total. if you have 4x 120GB drives, then you'll have 240GB of space with level 0+1. (are you sure this is supported though?)
Or you could just run them off the controller but as single drives.
if one drive fails, and the other drive is still alive, then you still have your data.
mirroring really does do what the name suggests. it just writes the system data twice, once on each disk, at the same time, so that if you removed one disk from the array, you could just run it off an IDE controller, and never know it was on a RAID controller.
and in raid 1 (mirroring), if you use 2 disks of equal size, say 120GB each, you'll only see 120GB of available space under windows. This is half of the total capacity of the 2 drives.
in raid 0 (striping), you can use 2 disks or more. You nearly double your transfer rate with 2 disks, and increase it even more with more disks, but the gains diminish the more disks you add. You still keep the total capacity of the drives, so 2x 120GB in striping is 240GB. but, if one drive fails, you loose ALL the data.
raid level 5 offers security and speed, but requires several disks. with severall disks, it basically stripes the system data + parity data to all the drives, and if one drive fails, the data on that drive can be rebuilt from the parity data from all the other drives. Losing 2 disks at the same time leads to the loss of all data. The available space is equal to (number of drives - 1) x size of smallest disk. You need at least 3 drives for this setup.
another possibility is level 1+0, basically a mirror array made up of 2 striped arrays. You need at least 4 drives for this kind of setup. Your storage capacity will be half of the total capacity of all your drives--------------------------------------------------------------------------
with your controller, you wrote that you have the options of 0, 1, or 0+1, so if you only have 2 disks of 120GB, then the only options are level 0 for speed (with capacity of 240GB), or level 1 for security (with capacity of 120GB).
If you want to use 0+1, you'll need to get 2 more drives, so you have 4 in total. if you have 4x 120GB drives, then you'll have 240GB of space with level 0+1. (are you sure this is supported though?)
Or you could just run them off the controller but as single drives.
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also raid 0+1 is not raid 10.... if i do 0+1 when one disk fails the RAID will just become RAID 0.. i don't quite get it. 
