Hi, I'm about to make a switch our KVM systems from Debian using libvirt to Proxmox, for now I started with one server, and I'm trying and I'm documenting.
Since now all the disks we use in recent systems are SSDs, I also reviewed the type of VM disks. From pre-allocated raw files, for greater performance (particularly on hdd) and greater flexibility to lvm thin.
Lvm as removing one FS layer should decrease the total needed write and increase the life of SSD disks, or I'm wrong?
Thin as preallocated is not needed anymore to decrease fragmentation now that we use SSD, and therefore we have the possibility of using snapshots. To free up the no longer used space the important thing seems to be having the trim enabled working in the VM, and beyond that no "compactions" or similar are necessary to free up the no longer used space, right?
Then I know that we will have to be careful not to have the total disk size larger than that of the physical disks (a problem that did not arise with pre-allocated raw disks).
Is there perhaps something relevant that I am not aware of or have not taken into account?
About VM disk cache however I have doubts about which one is best to use, I have seen some documentation on Proxmox, for example https://pve.proxmox.com/wiki/Performance_Tweaks#Disk_Cache and other outside (remaining within the QEMU scope), but I found some dubious or conflicting information.
My employer would like to set up writeback which I even had intentions of discarding it as write caching no longer seemed necessary with SSDs so we would risk less in the event of brutal shutdowns, or I'm wrong?
I did some research on using writeback with SSD and found conflicting opinions.
Thanks for any reply and sorry for my bad english.
Since now all the disks we use in recent systems are SSDs, I also reviewed the type of VM disks. From pre-allocated raw files, for greater performance (particularly on hdd) and greater flexibility to lvm thin.
Lvm as removing one FS layer should decrease the total needed write and increase the life of SSD disks, or I'm wrong?
Thin as preallocated is not needed anymore to decrease fragmentation now that we use SSD, and therefore we have the possibility of using snapshots. To free up the no longer used space the important thing seems to be having the trim enabled working in the VM, and beyond that no "compactions" or similar are necessary to free up the no longer used space, right?
Then I know that we will have to be careful not to have the total disk size larger than that of the physical disks (a problem that did not arise with pre-allocated raw disks).
Is there perhaps something relevant that I am not aware of or have not taken into account?
About VM disk cache however I have doubts about which one is best to use, I have seen some documentation on Proxmox, for example https://pve.proxmox.com/wiki/Performance_Tweaks#Disk_Cache and other outside (remaining within the QEMU scope), but I found some dubious or conflicting information.
My employer would like to set up writeback which I even had intentions of discarding it as write caching no longer seemed necessary with SSDs so we would risk less in the event of brutal shutdowns, or I'm wrong?
I did some research on using writeback with SSD and found conflicting opinions.
Thanks for any reply and sorry for my bad english.