Extending a LVM2 strip set
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Quoted 8 lines · [email protected] writes:
http://www.tldp.org/HOWTO/LVM-HOWTO/mapmode.html
<http://www.tldp.org/HOWTO/LVM-HOWTO/mapmode.html> states:"In LVM 2, striped LVs can be extended by concatenating another set of devices onto the end of the first set. So you can get into a situation where your LV is a 2 stripe set concatenated with a linear set concatenated with a 4 stripe set. Are you confused yet?"
Quoted 4 lines
As a matter of fact, I am!
I need to start with a 2 disk (therefore, 2 stripe) logical volume, that I later extend with 2 more disks. How is this done?
In lvm2 you simply create the lv with a stripe size of 2, then later when you want to extend it, you lvextend it with a stripe size of 2. The reason this is explained in so much detail is that in LVM1, you could not extend a striped set past its original PVs. In LVM2, the original striped set can be extended to the end of the original PVs, and any additional PVs become a striped set that is tacked on to the end (concatenated).
Maybe an ACSII picture can help ;)
Original striped volumes:
___ ___
| 1 | | 2 | | 3 | | 4 | |_5_| |_6_|
After adding two more disks and lvextending:
___ ___ ___ ___
| 1 | | 2 | | 7 | | 8 | | 3 | | 4 | | 9 | | 10| |_5_| |_6_| |_11| |_12|
So you have 2 sets of striped segments (with 2 stripes each), concatenated together. It does *not* remap all the striping so you have 1 set of striped segments (with 4 stripes each).
Is that any clearer?
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