On the server we have 4x80GB HDD and we are looking at upgrading the HD too all 250GB now is it possible to add the HDD and leave the Master 80GB HDD in and copy all that information to the 250GB then remove that 80GB and replace that with a 250GB then get the information copy back onto that.
I hope someone can help and understand what i'm trying to ask. Thanks if u can..
Level 5 : Striping with distributed parity.
Data and parity is striped across 3 or more drives. Parity is distributed to each drive. Level 5 is the most widely used RAID for servers and other highperformance storage solutions. Any single drive can fail without data loss, ie. at least two drives must fail before any data is lost.
"RAID alone is not a backup." You should have a backup of your data in place some where. All you would need to do then would be to take the system offline, refresh the backup, drop the array, create the new array, and restore the data from backup.
If you don't have a backup, then there are a couple of other possibilities, but these are risky and slower. You should always mention the chipset/board/etc. details of your RAID implementation, as they vary quite a lot, and have different features, issues, etc..
A. Most RAID 5 implementations will allow you to substitute a single drive of larger capacity at a time, but this would be a very slow process. Disconnect a 80 GB drive (array is degraded), connect a 250 GB drive in its place. Add it to the array (implementation-dependent details). Run the data restoration / rebuild process. This will take a long time for each drive. At the end, you'd still need to do expand the array from a 4 x 80 GB space allocation to 4 x 250 GB space, and again this detail is RAID implementation-dependent, and some RAID implementations might not even be able to do this.
B. Alternatively, you could create a temporary backup using one of the 250 GB drives, and use a RAID expansion feature, as available.
1. Copy all the data off the 80 x 4 RAID 5 array to a single 250 GB drive.
2. Disconnect the 80GB x 4 array.
3. Create a new 250 GB x 3 array.
(*) This step requires the knowledge of some rudimentary OLCE expansion features of your RAID implementation. E.g. for Intel motherboard-based RAID, you can't expand RAID 5 arrays, but you can convert and expand RAID 0 arrays. So for an Intel implementation, you could create a 2x or 3 x RAID 0 array, and later expand and convert that to 4 x RAID 5. With others, you could start off with a smaller RAID 5 array and expand it to a larger one.
4. Restore the data from the other 250 GB drive onto the new array.
5. Convert/expand the array to 4 x 250 GB as per (*).
6. Expand the file system to the additional space given in step (5). You might need a third-party utility to do this, depending on the file system / OS.
Steps (5), (6), and all of (A) are risky, because they're non-trivial operations which would be run without any backup at this point. Doing this sort of thing without a backup is highly discouraged.
All this gets more complicated if you have the OS also installed on the RAID 5 array, which is one of the main reasons that installing the OS on a separate drive/array is often recommended and done.