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Notes of making two 2TB WD Cavair Green (WD20EARS) drives into a RAID 1, LVM, XFS set.

I am adding two of these drives to an existing system. In this system they are connected to their own PCI SATA card which has made the disks /dev/sda and /dev/sdb. This system boots from a completely different disk.

These disks lie. They say they have 512 byte sectors, but they are actually 4096 byte sectors. So, even though we are going to partition the disk by 512 byte sectors we have to make the partition on boundaries of 8 of those sectors.

These drives want to park their disk heads after 8 seconds on inactivity, which adds up to a lot of parking. The Internet forums suggest using hdparm to set that time to 1 hour. The best way to persist that is to put these lines into /etc/rc.local

/sbin/hdparm -S 242 /dev/sda /sbin/hdparm -S 242 /dev/sdb


Use fdisk -u to make the parition by sectors.

Use the 'n' option to create a new partition.

Start at sector 64 (divisible by 8) and continue to the end of the disk.

Use the 't' option to change the partition to type 'fd'.

Use the 'w' option to write the partition table out, and quit.

Test the speed:
sudo /sbin/hdparm -tT /dev/sda1 sudo /sbin/hdparm -tT /dev/sda2


Create the RAID1 (mirror set)
sudo /sbin/mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sd[ab]1
Check it looks ok - possably echo that into /etc/mdadm/mdadm.conf:
sudo /sbin/mdadm --examine --brief --scan --config=partitions
Test the speed:
sudo /sbin/hdparm -tT /dev/md1


Initalise the Physical Volume:
sudo /sbin/pvcreate /dev/md1
sudo /sbin/pvdisplay
Create the Volume Group:
sudo /sbin/vgcreate -s 16M lvm-raid1_md1 /dev/md1
sudo /sbin/vgdisplay lvm-raid1_md1
Create the Logical Volume:
sudo /sbin/lvcreate -l 100%FREE lvm-raid1_md1 -n media
sudo /sbin/lvdisplay /dev/lvm-raid1_md1/media
Test the speed:
sudo /sbin/hdparm -tT /dev/lvm-raid1_md1/media


Create XFS partition:
sudo /sbin/mkfs.xfs -l internal,lazy-count=1 -d agcount=4 -b size=4096 /dev/lvm-raid1_md1/media
Mount - edit /etc/fstab:
/dev/lvm-raid1_md1/media /media/media xfs defaults 0 2

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