Dne 13.9.2017 v 04:23 matthew patton napsal(a):
I don't recall seeing an actual, practical, real-world example of why this
issue got broached again. So here goes.
Create a thin LV on KVM dom0, put XFS/EXT4 on it, lay down (sparse) files as
KVM virtual disk files.
Create and launch VMs and configure to suit. For example a dedicated VM for
each of web server, a Tomcat server, and database. Let's call it a 'Stack'.
You're done configuring it.
You take a snapshot as a "restore point".
Then you present to your developers (or customers) a "drive-by" clone (snapshot) of the
LV in which changes are typically quite limited (but could go up to full capacity) worth of
overwrites depending on how much they test/play with it. You could have 500 such copies resident.
Thin LV clones are damn convenient and mostly "free" and attractive for that purpose.
There is one point which IMHO would be way more worth to invest resource into
ATM whenever you have snapshot - there is unfortunately no page-cache sharing.
So i.e. you have 10 LVs being snapshots of the single origin you get 10
different copies of pages in RAM of the same data.
But this is really hard problem to solve...
Regards
Zdenek
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