Storage model enhacement

[e100]

I was reading a thread where @wbumiller mentioned that using O_DIRECT with mdraid can result in inconsistent arrays. https://forum.proxmox.com/threads/proxmox-4-4-virtio_scsi-regression.31471/page-2#post-159574

On DRBD we have the same issue where some cache types can result in out of sync blocks.

It would be nice if we could specify what cache methods cannot be used by a particular storage. Someone using mdraid could then disable directsync for the mdraid storage to prevent VM disks from using that method.

Another use case would be disabling all but the specific cache method you want all mvs on that storage to use. Example: only allow writeback for CEPH storage.

 

[dietmar]

Software RAID and DRBD should not use O_DIRECT (cache=none).

 

[e100]

Right

What I am suggesting is that it would be great if we could define the allowed cache types for a given storage.
That would allow me to prevent the use of specific cache types that are known to be bad for that particular storage.

Something like this in storage.cfg:

lvm: lms-storage

vgname mylvm
content images
shared
nodes A,B,C
cache_types cache=none, writethrough, writeback
cache_default writeback​

 

[dietmar]

What I am suggesting is that it would be great if we could define the allowed cache types for a given storage.
That would allow me to prevent the use of specific cache types that are known to be bad for that particular storage.

Please file a bug (feature request) at bugzilla.proxmox.com

 

[e100]

Done: https://bugzilla.proxmox.com/show_bug.cgi?id=1265

 

[Tarek Damak]

UP (Sorry i'm really in harry)