What RAID controllers can do expansion without data loss?

By pjstar27 ·
Background information: I currently have a full 1TB standalone drive (non-OS, just data). I'm planning to purchase 3 additional 1TB drives to run in RAID 5. Once I create the (3 drive) RAID 5 array I will copy the 1TB of data to the new array. After the data is copied to the new array I will then format the 1TB standalone drive at which point I want to add it to the (3 drive) RAID 5 array so that I have 4 1TB drives in the array. I want to add this 4th drive without having to rebuild the existing array.

Which hardware RAID controller would allow me to expand the RAID 5 array from 3 drives to 4 without rebuilding the array?

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Most new controllers

by hondafrank In reply to What RAID controllers can ...

Most new controllers should be able to handle this. I personally prefer Intel myself. This may do you well:


Remember though that when you add the disk to the system it won't be added to an existing disk. Will be added as a new raw partition. You can use 3rd party software to add this to the OS.

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More info please

by pjstar27 In reply to Most new controllers

Thanks for the reply.

From what I've read the RocketRAID cards have OCE (Online Capacity Expansion) that allows you to add a drive and then it automatically "rebuilds" the array to include the new drive, without data loss. The "without data loss" is the important part for me. Does the Intel controller you mentioned in your post allow this?

Would OCE negate the need for 3rd party software? My understanding is that it integrates the new drive into the array automatically. I might be off base here... that's why I'm asking.

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volume at the filesystem level

by Churdoo In reply to More info please

This all looks right. As Honda indicated, most current cards should do this.

I think where there's a disconnect is that once you extend the array after adding disk #4, the O/S will see the same size filesystem/volume as it had before, but it will look to the O/S like it's sitting on a larger disk (with unused capacity at the end). Is this a Windows O/S by the way?

Once the ARRAY is extended to include the additional disk (again, with most cards this should be non-destructive), you'll have to manually extend the filesystem volume. If this is a Windows O/S, and since you did say that this is NOT the system volume, this is easily accomplished with DISKPART, and also should be non-destructive. DISKPART is not third-party as it is a command-line utility included with Windows. You can Google info on DISKPART or repost questions here as needed.

Of course, you'll still want to have a good, tested backup "just in case."

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by pjstar27 In reply to volume at the filesystem ...

Thanks for the extra info. I see what Honda meant now that you explained it a little differently. I've used DISKPART before so I shouldn't have any issue. I'm really just praying for the "non-destructive" part because unfortunately I don't have a backup or even anywhere to fit a 1TB backup. This is partly why I'm installing a RAID 5... my data will be safer than just running on a single drive. I used Active@ Boot Disk, which is based on WinPE 2.1, in the past for images but the compression is really bad so you have to have a nearly equal amount of space just to keep the backup on.

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by hondafrank In reply to Thanks.....

Do try and make a backup before you do any of this. At the least you can pick up a 2TB USB drive for around $150 CDN. In my 14 years in IT I've run into many instances where things don't go as planned and if I didn't have backups I would have been screwed!

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