I'm not totally sure what you are saying, but I'll take a shot.
You have 4 disks in a RAID 5 array.
You swapped in 2 new disks one at a time, restriping the array after each drive was installed.
If that is correct, what were your original drives sizes? RAID 5 expects uniform drive sizes. IOW, if you had 4x36GB originally, adding in a new 74GB drive to the array would cause the array only to stripe on 36GB of that drive. You would still see physical free space on the new disk because the controller knows it is a 74GB drive, but the array can't use it because it is limited to utilizing only the amount of the smallest drive in your array. You can't stripe a 72GB data write onto a 36GB drive, but you can stripe 36GB onto the 74GB.
I'm really guessing here, as I am much more familiar with generic RAID concepts and different controllers than the particulars of the Dell PERC line.
Is there a limit to the number of containers that you can create on one PERC? Perhaps if you deleted the RAID 0 you created on the first 74GB drive and then tried to create another container using space from the two new drives?
However, I really have to wonder what sort of performance hit you will take using the same physical disk as parts of 2 different logical arrays? Given that your stripe size is 18GB, you are giving up 112GB total for the new drives so I can definitely see your wanting to utilize that space;)
Why not upgrade all of the drives to 74GB and just create a new array or add an external disk pack with the new drives and leave your existing array alone?
Sergey_M
2 Posts
0
February 12th, 2004 17:00
I had 18Gb * 4 hard drives
After I changed 1 HD I had free space on it. I tried to create new RAID0 container using this free space and it was OK.
I changed 1 more HD and now I can not create RAID1 or RAID0 container using free space.
PrattTech
5 Posts
0
February 12th, 2004 17:00
You have 4 disks in a RAID 5 array.
You swapped in 2 new disks one at a time, restriping the array after each drive was installed.
If that is correct, what were your original drives sizes? RAID 5 expects uniform drive sizes. IOW, if you had 4x36GB originally, adding in a new 74GB drive to the array would cause the array only to stripe on 36GB of that drive. You would still see physical free space on the new disk because the controller knows it is a 74GB drive, but the array can't use it because it is limited to utilizing only the amount of the smallest drive in your array. You can't stripe a 72GB data write onto a 36GB drive, but you can stripe 36GB onto the 74GB.
PrattTech
5 Posts
0
February 12th, 2004 18:00
Is there a limit to the number of containers that you can create on one PERC? Perhaps if you deleted the RAID 0 you created on the first 74GB drive and then tried to create another container using space from the two new drives?
However, I really have to wonder what sort of performance hit you will take using the same physical disk as parts of 2 different logical arrays? Given that your stripe size is 18GB, you are giving up 112GB total for the new drives so I can definitely see your wanting to utilize that space;)
Why not upgrade all of the drives to 74GB and just create a new array or add an external disk pack with the new drives and leave your existing array alone?