Fork Data Attribute records contain references to a maximum of eight extents that can hold larger attributes. Extension Attributes are used to extend a Fork Data Attribute record when its eight extent records are already used. The Startup File is designed for non-Mac OS systems that lack HFS or HFS Plus support. It is similar to the Boot Blocks of an HFS volume. The second-to-last sector contains the Alternate Volume Header, which is equivalent to the Alternate Master Directory Block of HFS. Note that this is the second-to-last-sector for the disk, not the volume; if the disk is larger than the volume, the AVH will be outside the range of the filesystem. The last sector in the volume is reserved for use by Apple. It is used during the computer manufacturing process. Criticisms HFS Plus lacks several features considered staples of modern file systems like ZFS and NTFS. Data checksums are the most routinely cited missing feature. Besides checksumming, features of modern file systems that HFS+ lacks include: nanosecond timestamps concurrent access (that is, more than one process can access the filesystem at the same time) snapshotting Support for dates beyond February 6, 2040 sparse file support a better implementation of hard links (in other filesystems, these are typically multiple directory entries pointing to the same data blocks; hard links in macOS are implemented as small files that are stored in a special hidden directory) HFS Plus was not designed for Unix-like systems, so features such as file system permissions and hard links had to be retrofitted when Apple moved to Mac OS X. Other operating systems Linux The Linux kernel includes the hfsplus module for mounting HFS+ filesystems read-write. HFS+ fsck and mkfs have been ported to Linux and are part of the hfsprogs package. In 2009, these drivers were diagnosed to be corrupting HFS+ drives with a capacity greater than 2 TB. Consequently, Linux distributions such as Debian and Ubuntu stopped allowing mounting of HFS+ drives or partitions greater than 2 TB. , work is in progress to lift this restriction. Under Linux's current HFS+ driver, journaling must be disabled in order to write data safely onto an HFS+ partition. Provided the partition isn't being used by Apple's Time Machine software, journaling can be disabled under macOS: Using Disk Utility in OS X Yosemite, the user may hold Alt/Option and click "Disable Journaling" on the File menu, having