Dne 19. 04. 19 v 21:30 Konstantin Ryabitsev napsal(a):
Hi, all:
I know it's possible to set up dm-cache to combine network-attached block
devices and local SSDs, but I'm having a hard time finding any first-hand
evidence of this being done anywhere -- so I'm wondering if it's because there
are reasons why this is a Bad Idea, or merely because there aren't many
reasons for folks to do that.
The reason why I'm trying to do it, in particular, is for mirrors.kernel.org
systems where we already rely on dm-cache to combine large slow spinning disks
with SSDs to a great advantage. Most hits on those systems are to the same set
of files (latest distro package updates), so dm-cache hit-to-miss ratio is
very advantageous. However, we need to build newest iterations of those
systems, and being able to use network-attached storage at providers like
Packet with local SSD drives would remove the need for us to purchase and host
huge drive arrays.
Thanks for any insights you may offer.
Hi
From lvm2 POV - if you put both devices into single VG - you should be able
to easily configure the setup in a way, that your 'main/origin' LV sitting on
network storage and cache is setup to be located on SSD.
lvcreate -LMAXSIZE --name MYLV vg /dev/networkshdd
lvcreate --cache -Lcachesize vg/MYLV /dev/ssd
But of course as Mike points out - cache currently expects the origin device
is reliable one.
Regards
Zdenek
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