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Thin provisioning allows volumes to grow or shrink as needed, instead of creating fixed volume sizes as storage administrators once did.įor example, Apple said, an APFS container with a capacity of 100GB that contains volume A, using 10GB, and volume B, using 20GB, would report the free space for both volumes A and B is 70GB. The feature is similar to another used by enterprises called "thin provisioning," which uses virtualization to give the appearance of having more capacity than what is actually available. "Unlike rigid partitioning schemes, which pre-allocate a fixed amount of space for each file system, APFS volumes can grow and shrink without volume repartitioning," Apple said.Įach volume in an APFS container reports the same available disk space, which is equal to the total available disk space of the container. "On APFS, TRIM operations are issued asynchronously from when files are deleted or free space is reclaimed, which ensures that these operations are only performed once metadata changes are persisted to stable storage," Apple said.Īpple also introduced "Space Sharing" in APFS, which allows multiple file systems to share the same underlying free space on a physical volume. In terms of SSD optimization, APFS - like HFS+ on which it is based - supports TRIM operations, which delete blocks of data no longer in use in order to free up capacity. "APFS combines both of these features into a unified model that encrypts file system metadata," Apple's guide said. In iOS, a version of data protection that encrypts each file individually with its own key has been available since iOS 4, according to the iOS Security Guide. In its desktop OS, full-disk encryption has been available since OS X 10.7 Lion. APFS encryption uses AES-XTS or AES-CBC, depending on hardware. It doesn't cost appreciably more," he said.Īpple did not respond to a request for comment by Computerworld on its new file system's features.Īccording to Apple's AFPS guide, the system allows users to choose several encryption modes for each volume in a container, including: no encryption, single-key encryption or multi-key encryption with per-file keys for file data and a separate key for sensitive metadata. "Roughly half of all of today's SSDs are already self-encrypting. Handy also questioned why Apple would need to create an encryption function in its file system when many SSDs today come native with the feature. If that's the case, there will be many cases when these won't be helpful because of a lack of connectivity," Handy said. "If this is an OS for laptops., then neither of these make sense, unless all the snapshots and replication are copied to the cloud. But he also cautioned that they're only as good as the second storage device to which they copy.
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"This is an issue for iPhone users: The automatic software updates nibble away at the iPhone's storage until there's so little left that the device barely functions - even if you have removed all of your own pictures, music, videos, and downloaded apps," Handy said.ĪPFS's snapshot and replication features, Handy said, are two important storage services that data center storage area networks (SANs) support. Technically, Handy said, anything that frees up space on the SSD or a hard disk drive "should be a good thing," as drives perform faster with more free capacity on which to write. "Is it a good thing to do that on a computer?" "As for the software automatically moving old files into the cloud, isn't this the same new feature of iTunes that got users so upset recently?" said Jim Handy, principal analyst at market research firm Objective Analysis. "These may be features IBM and Cisco asked for, but they will likely have to market them for people to care and neither has done any user focused marketing for some time having divested or shut down their consumer/user focused efforts."įor BOYD users in the workplace, the automatic migration feature might even violate corporate security policies, Enderle said. "Storage features on PCs are very difficult to sell," he said via email.