The Disk Center
Many factors can affect the performance and outcome of a backup task. One of the things that we have found particularly helpful for identifying performance problems, for example, is to have disk activity statistics available during a backup. CCC's Disk Center provides this kind of statistics monitoring, as well as general volume information for each locally-attached volume mounted on your Mac. Choose "Disk Center" from CCC's Window menu to view the Disk Center.
Basic volume information
The Disk Center window displays a list of locally-attached, mounted volumes in a table on the left. Click on one of these volumes to display information such as the volume name, filesystem, capacity, and disk usage. CCC displays a level indicator next to the disk usage figure. When disk usage exceeds 70% of the volume capacity, the level indicator will turn yellow to indicate that you may want to consider "cleaning house". If the disk usage exceeds 90% of the volume capacity, the level indicator will turn red. Especially on a volume that contains an installation of Mac OS X, we recommend that you try to maintain at least 10% of the volume as free space. When you start to consume that last 10%, fragmentation becomes a problem and general performance of Mac OS X begins to decline.
The Disk Center will update disk activity statistics on a one-second interval. Disk activity is collected by Mac OS X at the hardware interface, so data for multiple volumes residing on the same disk will be identical. The data read and write rate can give you a good indication of how fast Mac OS X is able to read and write data from and to your disk. You will likely notice that these values fluctuate wildly over the course of a backup task. This is quite normal, write performance will generally be lower when copying lots of small files and higher while copying a larger file. When lots of small files are being copied, there is a lot of seek activity occurring on your source and destination volumes. This seeking greatly reduces the overall throughput compared to the theoretical throughput of your disks.
If your backup task seems particularly slow, stop the task and see what the baseline disk activity is. For example, while running a performance test, I couldn't understand the absolutely dismal performance I was seeing. In the middle of the task I had launched Safari so I could download and test Growl on my test system, and I didn't think it would have a measurable affect on the task. I stopped the task and noticed a persistent 1.8MB/s level of write activity on my source volume in the Disk Center. After a brief investigation, I discovered that Safari was writing massive cache files to my home directory. After quitting Safari, my backup performance was back to normal.
Disk error statistics
CCC will report error-related statistics when they are present. You can tell at a glance that something is wrong with this disk:
Read and write latency is a cumulative measurement of the amount of time that the disk interface had to wait for a read or write operation to return data (in cases where the operation ultimately succeeded). Read and write retries indicates the number of times that the disk interface had to make multiple attempts to retrieve data (again, this value only pertains to attempts that were ultimately successful). Read and write errors indicate the number of read or write attempts that were simply unsuccessful. The meaning of each of these values is less important than their meaning as a whole. If you're seeing any red data in the Disk Center, there's a good chance that your hard drive is suffering a hardware problem.
Apple introduced a new "Full Disk Encryption" feature to Mac OS X Lion, and that functionality is exposed for Lion and Mountain Lion users in the Disk Center Encryption tab. CCC allows you to convert HFS+ formatted volumes that reside on a disk that is partitioned with the GPT partitioning scheme to FileVault encrypted volumes. You can also use the Disk Center to monitor the progress of the conversion process, and to disable encryption on a FileVault encrypted volume that was converted originally from an unencrypted volume. Please note that CCC is exposing functionality provided by the OS, CCC is not actually engaged in the encryption process. As a result, you can manipulate FileVault encryption with CCC's Disk Center, then close the window, quit CCC, run backup tasks, etc. while the conversion is handled by the OS.
Some considerations before you enable FileVault encryption on a volume
Your data will only be accessible on Mac OS 10.7 Lion (and later) Once the volume is encrypted, you will not be able to mount the volume on older versions of Mac OS X or on non-Mac operating systems.
The encryption key storage object is opaque CCC cannot (legitimately) manipulate this object to accommodate differences between two volumes. As a result, the interface upon startup will be limited to a generic "Unlock the disk" password field. When you encrypt a startup disk in the Security Preference pane (e.g. rather than in CCC's Disk Center), you get the following advantages:
- You can store your master key on Apple's servers, which could come in handy if you forget or lose your passphrase
- Any user account can unlock the volume and start the computer
- You get an elegant loginwindow-like UI on startup for your backup volume
If any of these advantages appeals to you, you can create your bootable, encrypted backup with these steps instead of converting the backup volume with CCC's Disk Center:
- Use CCC's Disk Center to create a Recovery HD volume on your backup disk.
- Perform an ordinary backup of your startup disk to your backup volume.
- Boot your Mac from the backup volume and enable FileVault 2 encryption in the Security preference pane.
- Reboot from your production installation of Mac OS X and carry on with ordinary usage and backup hygiene You do not have to wait for the encryption conversion to complete before rebooting to your production volume.
The conversion process may take a couple days Converting a volume to a FileVault encrypted volume requires that each block on the volume gets individually encrypted. This process works quietly in the background (consuming a modest amount of CPU), and you can use the volume during the conversion process, but it will result in a constant din of disk activity for many hours.
Please don't make the decision to encrypt a volume casually. Give the preceding limitations careful consideration and understand that encrypting a startup disk outside of the Security preference pane is unlikely to be an Apple-supported configuration.
Enable encryption on a volume
To enable FileVault encryption on a volume, click on the volume, then click on the "Enable encryption on (volume name)" button in the Encryption tab. CCC will prompt you to provide an encryption password for the volume, and offers the convenience of adding that password to your keychain. You will need this password to unlock the volume whenever it is attached to your Mac. CCC will store this passphrase in a private keychain so the volume can be mounted automatically during a scheduled backup task.
Disable encryption on a volume
Encryption can be disabled on any volume that was converted to FileVault encrypted from an unencrypted format, and that is not currently in the process of converting to an encrypted volume. To disable FileVault encryption on a volume, click on the volume, then click on the "Disable encryption on (volume name)" button in the Encryption tab. CCC will prompt you to provide your encryption password for the volume, then will begin the process of converting the disk to an unencrypted volume. Note that the decryption process will also take a considerable amount of time, and cannot be cancelled. You can continue to use and access the volume during the decryption process, and you do not need to have CCC open for the process to continue.
Starting with Mac OS X Lion, the Mac OS X Installer creates a new, hidden volume on your startup disk named "Recovery HD". The primary purpose of the Recovery HD volume is to offer a method to reinstall Mac OS X (Apple no longer distributes the Mac OS X Installer on a DVD). When performing a backup of a Mac OS X volume, Carbon Copy Cloner automatically archives the Recovery HD volume that is associated with the source volume to a disk image. This archive can later be restored to another Recovery HD volume. CCC's Disk Center also offers the ability to create a new Recovery HD volume on your destination disk.
Creating a new Recovery HD volume
Drobo devices do not support dynamic volume resizing (reference), and therefore cannot accept a Recovery HD volume. Do NOT attempt to create a Recovery HD volume on a Drobo device.
The Recovery HD volume is approximately 650MB, so to create a new Recovery HD volume, you must choose a volume on your disk that has at least 1GB of free space available. This documentation will refer to the chosen disk as the "donor" disk. No data will be harmed on the donor disk, it will simply be resized so some space can be allocated for the new Recovery HD volume. When you click the button to create a new Recovery HD volume, CCC will do the following:
- Unmount the donor disk
- Perform the equivalent of Disk Utility's "Verify disk" tool
- Resize the donor volume to (size of the donor volume) - 1GB
- Create a new volume named Recovery HD using the 1GB of borrowed space
- Clone a suitable Recovery HD volume from another disk (such as the startup disk) or an archive of the Recovery HD volume onto the newly-created Recovery HD volume
- Remount the donor volume
When the task has completed, the Recovery HD volume will not be mounted on your Desktop, nor will it appear in Disk Utility (it's a very special, very hidden volume!). You can verify the functionality of this Recovery HD volume by holding down the Option key on startup, then selecting the Recovery HD volume as the startup disk.
Re-cloning an existing Recovery HD volume
If you choose a volume on a disk that already has a Recovery HD volume, CCC will indicate that you may "Re-clone the Recovery HD volume on this disk". There are two scenarios in which you might need to re-clone the Recovery HD volume on a disk: 1) The Recovery HD volume is invalid, or its partition type is invalid (and it appears on your Desktop) or 2) an update to Mac OS X updates the Recovery HD volume on your startup disk, and you want to apply those changes to the Recovery HD volume on another disk.
When do I need to create a Recovery HD volume?
CCC bootable backups offer similar functionality to the Recovery HD volume, so the Recovery HD volume is not strictly required on a backup volume. Unless you have a specific reason to not create a Recovery HD, though (e.g. because it could affect a Boot Camp partition on the same disk, you don't want to give up the 1GB, etc), we recommend that you maintain a Recovery HD volume on your backup disk. Especially if you intend to use your destination volume in production (e.g. you are migrating to a larger disk, or restoring to a replacement disk), or if you intend to enable encryption on a volume on the backup disk, then you should create a Recovery HD volume on the destination disk. If you intend to enable encryption on the destination volume, we recommend that you create the Recovery HD volume before enabling encryption. A Recovery HD volume is not required for restoring an installation of Mac OS X from a CCC bootable backup.
What is the difference between archiving the Recovery HD and creating a new Recovery HD?
During the course of an ordinary backup of a volume that contains Mac OS X, CCC will automatically create an archive of the Recovery HD associated with that volume. This archive is stored on the source volume, and is subsequently backed up to the backup volume along with everything else. This archive of the Recovery HD volume can be used in the future to create a new Recovery HD. The archive is not, however, an operational Recovery HD volume, it's just a backup file.
CCC's Disk Center offers the ability to create an operational Recovery HD volume as well. This functionality is completely separate from creating an archive of the Recovery HD. Unlike the archiving of the source Recovery HD, creating a new Recovery HD is not something that happens automatically, you have to ask CCC to do this in the Disk Center. When CCC creates a new Recovery HD, it borrows space from your destination volume to create a new, hidden volume on that disk. The resulting Recovery HD is fully operational — you can boot your Mac from it and reinstall Mac OS X. Refer to the previous section to determine if creating a Recovery HD is required in your situation.
Why were other volumes on my disk unmounted when I created a Recovery HD?
CCC uses a command-line version of Disk Utility to resize the donor volume. Resizing that volume requires making changes to the partition table on the disk, and Disk Utility may choose to unmount other volumes on the disk while it makes those changes. CCC will specifically remount the donor volume, but whether Disk Utility remounts the other volumes is a function (or bug) of Disk Utility. You can remount these volumes manually in Disk Utility.
Can I configure CCC to not automatically archive the Recovery HD onto my source volume?
Yes. Choose "Preferences" from the Carbon Copy Cloner menu and uncheck the box next to "Automatically create an archive of Apple's Recovery HD volume".
No, not with CCC. Creating a Recovery HD requires borrowing space from a physical volume, and that is not a modification that we recommend making to an underlying member of an Apple Core Storage logical volume. The only Apple-supported method of creating a Fusion volume is via Disk Utility or the Mac OS X Installer, and each of those will create a Recovery HD volume before the Fusion volume is created. If you intend to create your own Fusion volume using one of the various tutorials available on the Internet, and if you want that volume to have an associated Recovery HD volume, we strongly recommend that you create a Recovery HD volume before creating the Fusion volume. You can use CCC to create the Recovery HD volume on the slowest disk that you intend to add to the Fusion logical volume group. See the following document for a demonstration.
- I want to clone my entire hard drive to a new hard drive or a new machine
- I want to backup my important data to another Macintosh on my network
- I want to backup multiple machines or hard drives to the same hard drive
- I want my backup task to run automatically on a scheduled basis
- Backing up to/from network volumes and other non-HFS volumes
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- How long should the clone or backup take?
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- "The disk usage on the destination doesn't match the source -- did CCC miss some files?"
- Will CCC clone the "Recovery HD" partition on Lion?
- Some applications behave differently or ask for the serial number on the cloned volume. Did CCC miss something?"
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