Raid and Sync in Linux
if you want to see the raid sync live then you can use the following command
watch cat /proc/mdstat
if you don’t want to see life, you just want to see finish or not then you need to use the below command
cat /proc/mdstat
or
more /proc/mdstat
for example if you are using raid1 and one of the hard disk got issue, then you need to change the hard disk and sync it with the other hard disk, you want to make mirror, so you need to follow the below instruction
to see the partition list you need to run the below command
fdisk -l
then you will see almost same like the below result
root@bear1 [/home/wpcsbco]# fdisk -l
Disk /dev/sda: 1500.0 GB, 1500084436992 bytes
255 heads, 63 sectors/track, 182374 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 208813+ 83 Linux
/dev/sda2 27 5248 41945715 82 Linux swap / Solaris
/dev/sda3 5249 8381 25165822+ 83 Linux
/dev/sda4 8382 182374 1397598772+ 5 Extended
/dev/sda5 8382 10209 14683378+ 83 Linux
/dev/sda6 10210 12037 14683378+ 83 Linux
/dev/sda7 12038 12298 2096451 83 Linux
/dev/sda8 12299 182374 1366135438+ 83 Linux
Disk /dev/sdb: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 39162 314568733+ 83 Linux
Sda1 or 2 or 3 mean the patrrtion in the hard disk
but sda or sdb or sdc mean the hard disk device,
once you plug in the hard disk to the server, then you need to run Fdisk -l to see the new hard disk already added as sdb or sdc like that
for example if the new hard disk added as sdb then you need to make the partition before syn, and make sure the partition same like the first hard disk partition
for example the first harddisk partition is below
(Figure 2)
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 208813+ 83 Linux
/dev/sda2 27 5248 41945715 82 Linux swap / Solaris
/dev/sda3 5249 8381 25165822+ 83 Linux
/dev/sda4 8382 182374 1397598772+ 5 Extended
/dev/sda5 8382 10209 14683378+ 83 Linux
/dev/sda6 10210 12037 14683378+ 83 Linux
/dev/sda7 12038 12298 2096451 83 Linux
/dev/sda8 12299 182374 1366135438+ 83 Linux
How to get the above result? you need to run this command fdisk /dev/sda
Then after that you need to press “P” command to show the partition details
you make sure that you write down all the details then after that you need to press “q” to quit
and go enter to new hard disk to make the partition first
for example the new harddisk is sdb
fdisk /dev/sdb
then press p you will see nothing there, then you need to press “n” to create the new partition
Once you press “n” then you will get two option
1- Extended
2- Primary
then you need to select primary
then will ask you the block sector starting point, you can get it from the main hard disk , refer to figure (2) , be inform that you are now working to do the sdb1 which is the first partition, and also will ask you about the end point, you can get it from the main hard disk which is form figure (2) why we use the result of hard disk one in the hard disk two? because they are must be same partition then the sync will be working fine, because raid1 mean two hard working as one hard, the second hard will be the mirror for the first hard disk
then after the end point you need to press “t” to select the fs type (file system type, which is mean linux, you can refer to figure (2) you will see linux using ID 83, that mean we need to use the same here in the second hard disk
that mean t used to select the file system type
“notes”
if you want to list and see all the tpye then you need to press “L” then you will see all the fs type, which is even you will find linux there using 83
after you done the partition for the sdb1 then you need to repeat the same step for sdb2 which is again press n to create the partition by referring to figure 2 and also t to select the file system type, which is i can see in the figure two that sda2 using swap which is 82, so that mean you need to use it for sdb2 as well
in the end to save what you have done then you need to press “w” which is mean write
or if you want to quit then you need to press “q”
———————–
i will list all the command used
p for list of partition
n for create partition
l for list of the file system type
w to save the change
q to quit
That is all and thank you.