Adding space to GPT RAID (Become an expert)

Adding disk space to a Redundant Array of Inexpensive Disks (RAID) can increase the storage capacity of the RAID. With large RAIDs, the GUID Partition Table (GPT) is often used because msdos partition tables are limited to 2 TB. Since the GPT stores a backup copy of the partition table at the end of the disk device, the GPT must be updated to take advantage of the increased storage capacity. The steps to update the GPT are covered in this recipe.

Getting ready

Add the extra disk space to your RAID. As RAID configurations vary widely in the hardware and software used, we leave the task of increasing the storage capacity of the RAID to you.

How to do it...

1. The following screen shot shows RAID prior to adding the extra disk space:

   

2. Boot GParted with the extra space already added to the RAID.

3. Optionally, if the following window is displayed then click on Fix.

   Note

   This window is displayed only when the RAID contains no partitions. If you choose Cancel or Ignore then you will not be able to use the recently added extra disk space.

   

4. Click on Fix when the following window is displayed.

   Note

   If you choose Ignore then you will not be able to use the recently added extra disk space.

   

5. The GPT now permits access to all of the RAID capacity.

   

How it works...

When extra disk space is added to RAID, the extra space is not immediately available for partitioning. This is because a GUID Partition Table has a backup copy of itself stored at the end of the device. To remedy this situation, update the GPT so that the backup partition table is moved to the end of the RAID. Then the GPT is able to see all of the extra storage capacity.

There's more...

If you do not fix the GPT, GParted will still show the additional disk space but you will be unsuccessful when applying operations that create or adjust partitions to use the additional disk space.

With today's larger disks devices and with support built into modern operating systems, GPT is taking over from the msdos partition table. One of the main reasons is that an msdos partition table cannot access partitions larger than 2 TB, or partitions that start beyond the first 2 TB of the disk device. Another reason is that GPT supports 128 primary partitions, whereas msdos is limited to 4 primary partitions.

Note that RAIDs that use msdos partition tables do not require this repair step because there is only one copy of the msdos partition table, which is located at the start of the disk device.

Reference information

For more information on RAIDand the GUID partition table, see http://en.wikipedia.org/wiki/RAID, http://en.wikipedia.org/wiki/GUID_Partition_Table.