![Hard Drive](http://static.howstuffworks.com/gif/adding-a-hard- disk-1-1.jpg)Well, I have just received the RMA replacement of my failed Samsung HD204UI 2TB drive.&nbsp_place_holder; Now it is time to put the drive back into my Linux server and rebuild the RAID-1 (mirror) array so that the data resumes its&nbsp_place_holder;highly-available state.&nbsp_place_holder; Here are the steps I took:

Install the hard drive.&nbsp_place_holder; Since I am not using hot-swap drive bays, I will have to shutdown the server to attach the drive the SATA-II controller.
Locate the disk (new disk is /dev/sdd). &nbsp_place_holder;This was found by looking at “fdisk -l”. &nbsp_place_holder;My replacement is the unpartitioned drive that has resumed the device spec of my failed unit.
A Linux RAID (fd) partition must be created on the new drive. Create the partitioning table on the new drive, /dev/sdd, identically to the drive in the array. Use the “sfdisk” command:

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sfdisk -d /dev/sdc > sdc_partition.out

sfdisk /dev/sdd < sdc_partition.out

Checking that no-one is using this disk right now … OK

Disk /dev/sdd: 243201 cylinders, 255 heads, 63 sectors/track

sfdisk: ERROR: sector 0 does not have an msdos signature &nbsp_place_holder;/dev/sdd: unrecognized partition table type Old situation: No partitions found New situation: Units = sectors of 512 bytes, counting from 0

&nbsp_place_holder;&nbsp_place_holder; Device Boot&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder; Start&nbsp_place holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_h older;&nbsp_place_holder; End&nbsp_place_holder;&nbsp_place_holder; #sectors&nbsp_place_holder; Id&nbsp_place_holder; System /dev/sdd1&nbsp_place holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_ho lder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_hold er;&nbsp_place_holder;&nbsp_place_holder; 63 3907024064 3907024002&nbsp_place_holder; fd&nbsp_place_holder; Linux raid autodetect /dev /sdd2&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_hold er;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder ;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder; 0&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;& nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder; -& nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nb sp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp place_holder; 0&nbsp_place_holder;&nbsp_place_holder; 0&nbsp_place_holder; Empty /dev/sdd3&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_pl ace_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_plac e_holder; 0&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_plac e_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_ holder; -&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_ holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_ho lder;&nbsp_place_holder; 0&nbsp_place_holder;&nbsp_place_holder; 0&nbsp_place_holder; Empty /dev/sdd4&nbsp_place_holder;&nbsp_place_holder;&nbs p_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_ place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_pl ace_holder;&nbsp_place_holder; 0&nbsp_place_holder;&nbsp_place_holder;&nbsp_pl ace_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_plac e_holder;&nbsp_place_holder; -&nbsp_place_holder;&nbsp_place_holder;&nbsp_plac e_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_holder;&nbsp_place_ holder;&nbsp_place_holder;&nbsp_place_holder; 0&nbsp_place_holder;&nbsp_place_holder; 0&nbsp_place_holder; Empty Warning: no primary partition is marked bootable (active) This does not matter for LILO, but the DOS MBR will not boot this disk. Successfully wrote the new partition table

Re-reading the partition table …

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1) to zero the first 512 bytes:&nbsp_place_holder; dd if=/dev/zero of=/dev/foo7 bs=512 count=1 (See fdisk(8).)

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Verify that the disk was partitioned properly and similar to the surviving drive. &nbsp_place_holder;In the example, I am comparing the partition tables of the drive currently in the RAID array with my new drive. &nbsp_place_holder;Notice that the newly created partition is /dev/sdd1 on my replacement drive /dev/sdd.

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sfdisk -l /dev/sdc

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Disk /dev/sdc: 243201 cylinders, 255 heads, 63 sectors/track

Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

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&nbsp_place_holder; &nbsp_place_holder;Device Boot Start &nbsp_place_holder; &nbsp_place_holder; End &nbsp_place_holder; #cyls &nbsp_place_holder; &nbsp_place_holder;#blocks &nbsp_place_holder; Id &nbsp_place_holder;System

/dev/sdc1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0+ 243200 &nbsp_place_holder;243201- 1953512001 &nbsp_place_holder; fd &nbsp_place_holder;Linux raid autodetect

/dev/sdc2 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

/dev/sdc3 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

/dev/sdc4 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

[root@aquila ~]# sfdisk -l /dev/sdd

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Disk /dev/sdd: 243201 cylinders, 255 heads, 63 sectors/track

Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

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/dev/sdd1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0+ 243200 &nbsp_place_holder;243201- 1953512001 &nbsp_place_holder; fd &nbsp_place_holder;Linux raid autodetect

/dev/sdd2 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

/dev/sdd3 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

/dev/sdd4 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; - &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder;Empty

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My degraded raidset is /dev/md3. &nbsp_place_holder;Here is it’s current status.&nbsp_place_holder;

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mdadm -v -D /dev/md3

/dev/md3:

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; Version : 0.90

&nbsp_place_holder; Creation Time : Sat Jun &nbsp_place_holder;4 21:34:09 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Raid Level : raid1

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Array Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; &nbsp_place_holder;Raid Devices : 2

&nbsp_place_holder; Total Devices : 1

Preferred Minor : 3

&nbsp_place_holder; &nbsp_place_holder; Persistence : Superblock is persistent

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&nbsp_place_holder; &nbsp_place_holder; Update Time : Tue Jul 12 20:27:30 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; State : clean, degraded

&nbsp_place_holder;Active Devices : 1

Working Devices : 1

&nbsp_place_holder;Failed Devices : 0

&nbsp_place_holder; Spare Devices : 0

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&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;UUID : 5de5eb25:d02318e7:da699fd5:65330895

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Events : 0.13444

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&nbsp_place_holder; &nbsp_place_holder; Number &nbsp_place_holder; Major &nbsp_place_holder; Minor &nbsp_place_holder; RaidDevice State

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 8 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 33 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;active sync &nbsp_place_holder; /dev/sdc1

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;0 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;removed

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Now I need to reconstruct the degraded RAID array with the partition on the new drive. &nbsp_place_holder;Since the replacement drive is now properly partitioned,it can simply be added to the array, /dev/md3, using the mdadm –manage command. &nbsp_place_holder;

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mdadm -v –manage /dev/md3 –add /dev/sdd1

mdadm: added /dev/sdd1

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Now taking a look at the /dev/md3 raidset, the new partition has been added as a spare and the array has automatically started recovering. &nbsp_place_holder;This is a 2TB drive, so it will take a little while to become in-sync.

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mdadm -D /dev/md3

/dev/md3:

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; Version : 0.90

&nbsp_place_holder; Creation Time : Sat Jun &nbsp_place_holder;4 21:34:09 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Raid Level : raid1

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Array Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; &nbsp_place_holder;Raid Devices : 2

&nbsp_place_holder; Total Devices : 2

Preferred Minor : 3

&nbsp_place_holder; &nbsp_place_holder; Persistence : Superblock is persistent

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&nbsp_place_holder; &nbsp_place_holder; Update Time : Tue Jul 12 20:27:30 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; State : clean, degraded, recovering

&nbsp_place_holder;Active Devices : 1

Working Devices : 2

&nbsp_place_holder;Failed Devices : 0

&nbsp_place_holder; Spare Devices : 1

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&nbsp_place_holder;Rebuild Status : 0% complete

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&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;UUID : 5de5eb25:d02318e7:da699fd5:65330895

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Events : 0.13444

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&nbsp_place_holder; &nbsp_place_holder; Number &nbsp_place_holder; Major &nbsp_place_holder; Minor &nbsp_place_holder; RaidDevice State

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;2 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 8 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 49 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;spare rebuilding &nbsp_place_holder; /dev/sdd1

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Here is what the healthy mdadm status of the 2TB mirror raidset looks like (after about 8-10 hours with my /proc/sys/dev/raid/&nbsp_place_holder;configurations):

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mdadm -D /dev/md3

/dev/md3:

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; Version : 0.90

&nbsp_place_holder; Creation Time : Sat Jun &nbsp_place_holder;4 21:34:09 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Raid Level : raid1

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Array Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)

&nbsp_place_holder; &nbsp_place_holder;Raid Devices : 2

&nbsp_place_holder; Total Devices : 2

Preferred Minor : 3

&nbsp_place_holder; &nbsp_place_holder; Persistence : Superblock is persistent

&nbsp_place_holder;

&nbsp_place_holder; &nbsp_place_holder; Update Time : Wed Jul 13 08:20:22 2011

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; State : clean

&nbsp_place_holder;Active Devices : 2

Working Devices : 2

&nbsp_place_holder;Failed Devices : 0

&nbsp_place_holder; Spare Devices : 0

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&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;UUID : 5de5eb25:d02318e7:da699fd5:65330895

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;Events : 0.13498

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&nbsp_place_holder; &nbsp_place_holder; Number &nbsp_place_holder; Major &nbsp_place_holder; Minor &nbsp_place_holder; RaidDevice State

&nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 8 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; 49 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;1 &nbsp_place_holder; &nbsp_place_holder; &nbsp_place_holder;active sync &nbsp_place_holder; /dev/sdd1

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That was all that there was to it. &nbsp_place_holder;If you follow these steps with your own server, your mileage may vary, so be careful. &nbsp_place_holder;Make sure that you take care of your data first and make a consistent, recoverable backup before you start. &nbsp_place_holder;Remember, a backup that has never been restored is not a backup.