The block_validity mount option spot-checks block allocations against a bitmap of known group metadata blocks. This helps us to prevent self-inflicted catastrophic failures such as trying to "share" critical metadata (think bitmaps) with file data, which usually results in filesystem destruction. In order to test the overhead of the mount option, I re-used the speed tests in the metadata checksum testing script. In short, the program creates what looks like 15 copies of a kernel source tree, except that it uses fallocate to strip out the overhead of writing the file data so that we can focus on metadata overhead. On a 64G RAM disk, the overhead was generally about 0.9% and at most 1.6%. On a 160G USB disk, the overhead was about 0.8% and peaked at 1.2%. When I changed the test to write out files instead of merely fallocating space, the overhead was negligible. Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --- misc/mke2fs.conf.in | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/misc/mke2fs.conf.in b/misc/mke2fs.conf.in index 178733f..3919f3b 100644 --- a/misc/mke2fs.conf.in +++ b/misc/mke2fs.conf.in @@ -1,6 +1,6 @@ [defaults] base_features = sparse_super,filetype,resize_inode,dir_index,ext_attr - default_mntopts = acl,user_xattr + default_mntopts = acl,user_xattr,block_validity enable_periodic_fsck = 0 blocksize = 4096 inode_size = 256 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
