Hi, I read from here https://patchwork.kernel.org/project/xfs/patch/20181110115104.30293-4-hch@ls... that I can enable COW on XFS fs but I can't find any switch for always_cow unders sysfs.
I'm running AlmaLinux 9.3.
Reading the man page of mkfs.xfs I found:
"reflink=value This option enables the use of a separate reference count btree index in each allocation group. The value is either 0 to disable the feature, or 1 to create a reference count btree in each allocation group. The reference count btree enables the sharing of physical extents between the data forks of different files, which is commonly known as "reflink". Unlike traditional Unix filesystems which assume that every inode and logical block pair map to a unique physical block, a reflink-capable XFS filesystem removes the uniqueness requirement, allowing up to four billion arbitrary inode/logical block pairs to map to a physical block. If a program tries to write to a multiply-referenced block in a file, the write will be redirected to a new block, and that file's logical-to-physical mapping will be changed to the new block ("copy on write"). This feature enables the creation of per-file snapshots and deduplication. It is only available for the data forks of regular files.By default, mkfs.xfs will create reference count btrees and therefore will enable the reflink feature."
This means that using reflink=1 enable COW on the FS and that it is enable by default on fs creation or I'm missing something?
Thank you in advance.
Best regards, Alessandro.