[linux-lvm] Question on mixing technologies

Georges Giralt georges.giralt at free.fr
Wed May 31 06:53:49 UTC 2017

Thank you, Gionatan for your answer.

I finally had time to test the first solution, having the root FS on the 
M.2 card and everything else (including /var and /tmp) on the mechanical 

The responsiveness of the machine is awesome and, for now, without any 
glitch or problem. So I may retain this solution.

The only remaining question is how to trim the device as it is not 
"mounted". Is there a special pvcreate or LVM option to have this device 
trimmed when it should be ?

Have a nicce day !

Le 13/05/2017 à 14:16, Gionatan Danti a écrit :
> You basically have two possibilities:
> 1) move the root fs on the M.2 disk, which will give you much higher 
> system responsiveness compared to the mechanical disks; however, any 
> data/application installed on the HDD will be slow as always;
> 2) configure lvmcache [1] for using the M.2 disk as a read-only 
> (writethrough) caching device for the mechanical disks, which will 
> give you somewhat lesser system responsiveness but *any* 
> cache-friendly application will be accelerated from the M.2 disk.
> [1] http://man7.org/linux/man-pages/man7/lvmcache.7.html
> Regards.
> Il 12-05-2017 18:21 Georges Giralt ha scritto:
>> Hello guys,
>> I've an Ubuntu machine with two SATA mechanical drives on software 
>> raid 1.
>> This md is the sole PV of the LVM installation.
>> As the mainboard has been changed recently, it has an M.2 plug. And
>> I'm been offered a 128 GB M.2 NGFF card.
>> So far so good.
>> Question : Will I gain something adding the M.2 card as a second PV on
>> my LVM setup and moving the system LV to it ?
>> What are your experience on the subject ?
>> Many thanks in advance for your advice !

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