I could use some insight into this confusing and maddening problem. I have a RocketRaid 1640 that for a number of years has been hosting a RAID 5 array made up of 4 drives, at 400 GB each. For the most part, it has performed very well, without major incident.
Recently I decided to upgrade by replacing all of the drives with 1TB drives. It took me many hours to copy all of my data off of the array and onto other media, then I destroyed it and swapped the old drives out for the new ones.
The RocketRaid BIOS utility recognized the four new devices, and correctly shows them all as having a capacity of 1000.20 GB. But after choosing to create a new RAID 5 array, selecting all four drives, and letting it build, the new array only has a capacity of 801.59 GB! I've repeated the process twice, trying to figure out what I could have done wrong, and I'm dumbfounded. The BIOS utility continues to show 4 devices of 1000.20 GB, all belonging to the RAID 5 array. . . which for some reason has a capacity of less than a single drive!
Just to get some more data on which to speculate, I played around with creating JBOD, RAID 0, and RAID 1 arrays instead. In all cases, if I used any 2 drives to make the array, I got the expected capacity; 1000.20GB for RAID 1, 2000.40GB for RAID0 or JBOD. But if I created a RAID 0 or JBOD array using 3 drives, I would get only 801.59GB. And if I created a RAID 0 or JBOD with all 4 drives, I'd get only 1801.79GB -- which is 801.59 + 1000.20.
Can anyone explain what gives? Am I running up against some limit of the controller card? For now I appear to be stuck doing RAID 1/0 (Which gets me the expected 2000.40GB), but that is not what I set out for when I started this upgrade. I didn't go to all this trouble and expense just to replace a 1.2 TB array with a 2TB array. I want my 3TB array!
Thanks in advance to anyone who may be able to help.
Your RocketRAID doesn't support volumes >2TB. You can see if there is a BIOS update for your RocketRAID card that enables >2TB support, but in all likelihood it is simply a limitation of the hardware on the card.
You will probably end up needing to replace your RAID card with a newer model that supports >2TB arrays.
Does the RocketRaid controller support multiple RAID arrays on the same set of disks? For comparison, the Intel Matrix Storage feature supports up to two arrays on 1 set of disks, so you can have a RAID 0 array and a RAID 5 array on the same 4 disks, each array using only a portion of the available disk space.
If RocketRaid supports something like that, then you could setup 2 x 1.5 TB arrays, and then use Disk Manager to join the two partitions back together again - probably as a concatenated array. Not only does that enable you to create your 3 TB array, but Windows XP (at least 32 bit Pro, anyway) doesn't allow for > 2 TB single (non-dynamic) arrays to begin with. So even if your RocketRaid supported it, your OS might not.
Of course if you're using Linux or other, then none of this will help you very much.