[linux-lvm] mixed ssd/disk szenario question: moving lv from ssd ->disk?

[Oliver Rath]

Hi list,

I have an vg over multiple disks (ssd and standard disks) and a big
thinpool-volume inside. From thin thinpool i create a lot of snaps
(>200), which are normally explizit placed on the ssd (i can select the
pv-path on lvcreate).

Now, after a time some of these snaps i dont need on the fast device and
want to mv them to a slow pv (standard disk) as a kind of backup.

Ist it possible to "move" a lv from the ssd to a disk, if both devices
are part of my vg?

Tfh!
Oliver

[matthew patton]

I think 'lvconvert --replace /dev/<ssd> VG/LV /dev/<slow disk>'
will do what you want.

[Oliver Rath]

Hi Matthew,

thank you for the hint! In the lvconvert-manpage they write:

"This option is only available to RAID segment types (e.g. raid1,
raid5, etc)"

So I assume this will not work with thinpool-devices, but using raid
with this trick is another good idea.

Tfh!
Oliver

Post by matthew patton
I think 'lvconvert --replace /dev/<ssd> VG/LV /dev/<slow disk>'
will do what you want.
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[Oliver Rath]

Hi Matthew,

i have to correct my last email: This works also with thinpool-lvs!
Better said: There was no error message executing this command. Will
walk on this way for more reults. Maybe the lvconvert-manpage is outdated?

Tfh!
Oliver

Post by matthew patton
I think 'lvconvert --replace /dev/<ssd> VG/LV /dev/<slow disk>'
will do what you want.
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read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

[Zdenek Kabelac]

Post by Oliver Rath
Hi Matthew,
i have to correct my last email: This works also with thinpool-lvs!
Better said: There was no error message executing this command. Will
walk on this way for more reults. Maybe the lvconvert-manpage is outdated?
Tfh!
Oliver

Hi


I'm somehow missing the point here.

Could you please show us 'lvs -a -o+seg_pe_ranges'

Normally when you make a thin volume snapshot, the snapshot is sharing your
blocks within thin-pool. So no space is allocated on any SSD for this.
(And you cannot specify which block will be used in a thin-pool)

If you would be using 'old-snapshot' which does allocate 'extra' space for COW
block -then you would probably see horrible performance with 200 snapshots...

And finally - standard command for moving extents around in a VG is - 'pvmove'.


Regards

Zdenek