Expanding a RAID1 array with bigger disk drives

Problem: You have an existing RAID1 array and now you need more disk space. You have purchased two identical 300 GB disk drives to replace the existing 147 GB disk drives. What is the quickest way to replace the disk drives with the least amount of down time?

Answer: This week I ran into a situation this week. The easy part of the answer was to replace one disk drive with a new 300 GB drive and let the RAID controller synchronize the drives. Then you replace the last 147 GB drive with the 300 GB disk drive. The hard part of the question was whether you could partition the remaining disk space into a logical volume without rebooting. The answer is yes. It took about a two and half hours to mirror the first disk. During the first hour Exchange was really sluggish. The next hour and a half the response time was okay. It took about an hour and a half to mirror the second drive. The response time was okay during the entire mirroring operation. When the mirroring was complete I used the Compaq/HP disk array software to check the disk drives. My research on Internet said that it was unlikely that the disk array software would show the disk space that was not part of the existing RAID1 array as being available. I was mildly amused to see that it showed that 292 GB was available(i.e. 146 GB per drive). I used the disk array software to create a 146 GB RAID1 volume. When I went into Disk Management I could see 146 GB was available to be partitioned and formatted. Except for the first hour of mirroring this whole operation was pretty painless and did not require a reboot.

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