Newbie ? on Filesystems, LVs and mirroring 1

[danshelb]

I'm a Unix newbie trying to decipher the differences and relationships between physical/logical volumes, volume groups, filesystems and physical/logical partitions.

This hopefully would help me with my main question, which is how to setup mirroring for some database and applications I'm setting up. I have 7 disks in an external array. I *think* that I'd like to have ext disks 1 and 2 be mirrored by disks 4 and 5, disk 3 be mirrored by 6 and disk 7 be a hot spare for any disk in the ext array that went down. Any help on how I could accomplish this? BTW, this is software mirroring, not on the hardware level.

Many thanks,
Dan

 

[Chacalinc]

what is your OS and level? basicly, the base is the same, but with different commands.

A Volume Group (VG) is a logical group of physical disk drives. A logical volume is a logical partition inside a Volume group, so in a logical volume (lvol) you make a file system. You can mirror logical volumes inside the volume group, so you say disks c1t0d0 and c2t0d0 are 2 different disks inside the same VG, and you create a lvol with 2 mirrors. Inside the lvol you make the file system.

for example:

disk1 | lvol1
disk2 |===> VG_data ==> lvol2
disk3 | lvol1' (mirror)
disk4 | lvol2' (mirror)

mount /dev/VG_data/lvol1 /mount_point_apps
mount /dev/VG_data/lvol2 /mount_point_data

disks 1 to 4 are grouped in VG_data, so VG_data is like 1 big disk drive, but you can mirror the lvols.

Hope this helps.

 

[danshelb]

Thanks Chacalinc. I'm running AIX 5.2L.

This definitely helps. I've been reared on Windows (no snickering please ;-) ) so my brain keeps trying to map Unix's disk/data structure to the more familiar Windows world. This clears things up. Thanks.

 

[bi]

Since you are new to Unix, I highly recommend you "swallow your pride" and let smit (or smitty if you don't have Xwindows) help you through this initial setup. You can look at the commands that have been/will be run, so if you want to do something similar again from the command line, you will have a better idea of the commands to use.