diff options
| -rw-r--r-- | man/man8/zfs.8 | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/man/man8/zfs.8 b/man/man8/zfs.8 index c4c172155..4cabf23ba 100644 --- a/man/man8/zfs.8 +++ b/man/man8/zfs.8 @@ -1275,6 +1275,19 @@ compression algorithm compresses runs of zeros. This property can also be referred to by its shortened column name .Sy compress . Changing this property affects only newly-written data. +.Pp +When any setting except +.Sy off +is selected, compression will explicitly check for blocks consisting of only +zeroes (the NUL byte). When a zero-filled block is detected, it is stored as +a hole and not compressed using the indicated compression algorithm. +.Pp +Any block being compressed must be no larger than 7/8 of its original size +after compression, otherwise the compression will not be considered worthwhile +and the block saved uncompressed. Note that when the logical block is less than +8 times the disk sector size this effectively reduces the necessary compression +ratio; for example 8k blocks on disks with 4k disk sectors must compress to 1/2 +or less of their original size. .It Xo .Sy context Ns = Ns Sy none Ns | Ns .Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level |