Reconfiguring Raid 5 on Perc 5i controller question

[dabbler]

Guys,

Understand the concepts of raid technology but just looking to clarify some of the specifics of management on a Perc 5i controller (on a Dell 2900 server).

Basically as far as I understand :-

1. For a raid 5 array - the array will utilise n times the smallest disk in the array (if using mixed disk capacities, and is supported by the controller).

However for future expansion capabilities (upgrading disks / adding disks) :-

2. Can the existing disks be increased in size while maintaining data integrity in the array (one at a time if necessary)?
3. How is the array capacity increased when increasing disks (is it after the last small disk is replaced - it will reconfigure to the larger disks)?
4. Some documentation (LSI) state the if more than one logical drive is held within an array, the array cannot be expanded - is this true?
5. If the array increases in size how is the logical drive increased (pro rata or does the user have to increase it)?


Thanks for any help on this.

 

[axan]

1 yes, array size is limited by the capacity of the smallest size, n * size of smallest disk (where n is the number of drives in the array)
2 yes, one disk at a time (have to wait for rebuild after each disk is replaced)
3 you can increase the size of the array after last smallest disk is replaced
4 not sure about that, i usually do just 1 partition
5 after you increase the size of the array you need to use other tools to grow the size of the partition and file system, specific tools would depend on the os used, if it's windows you could use something like partition magic or gparted.

 

[dabbler]

Thanks axan,

That's what I thought - will probably set fixed raid 1 on 2 drive and have system partitions there and then the rest as a raid 5 array with one partition for data.

I knew about the host OS issue (use growfs in linux or gparted/PM in Windows).

Jim.

 

[dabbler]

Not what I wanted to hear from Dell Tech Support.

Basically they said that any disks added to / removed from the array will be based on the smallest disk that was originally part of the array.

Looks like I will have to buy the largest practical disks today (750Gb) and start with these on raid 5 or use 2 x 1Tb disks in a raid 1 and migrate to raid 5 when the price becomes more realistic (future proofing).

 

[axan]

i think dell is full of $@# i would verify for you but i don't have per5i lying around atm; however any raid controller i ever worked with that could do oce would let you swap out smaller disks for bigger one at a time and then expand the capacity. I would do some more research before you buy the drives.