Q

snapraid.d

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+Name{number}
+	snapraid - SnapRAID Backup For Disk Arrays
+
+Synopsis
+	:snapraid [-c, --conf CONFIG] [-s, --start BLOCK]
+	:	[-f, --force] [-v, --verbose] [-e, --exclude PATTERN]
+	:	COMMAND
+
+	:snapraid [-V, --version] [-h, --help]
+
+Description
+	SnapRAID is a backup program for a disk array using redundancy.
+
+	SnapRAID uses a disk of the array to store redundancy information,
+	and it allows to recover from a complete disk failure.
+
+	SnapRAID is based on the snapshot concept like a backup program.
+	You decide the time to make the "sync" of the redundancy information,
+	and you are able to restore all the changes done at a disk of the array,
+	until the "sync".
+
+	The main features of SnapRAID are:
+
+	* You can start using SnapRAID with already filled disks.
+		You do not have to reformat or copy your data.
+	* The disks of the array can have different sizes.
+		You have only to use the biggest one for the redundancy data.
+	* The data in the disks is not changed in any way.
+		It doesn't even need write access at the data.
+	* If more than one disk fails, you lose the data only on the failed disks.
+		All the data in the other disks is safe.
+	* It doesn't lock-in your data.
+		You can stop using SnapRAID at any time.
+
+Misfeatures
+	SnapRAID is in between a RAID and a backup program trying to get the best
+	benefits of them. Altough it also has some downsides that you should
+	consider before using it:
+
+	* You have different filesystems for each disk.
+		Using a RAID you have only a big filesystem.
+	* It doesn't stripe data.
+		With RAID you get a speed boost with striping.
+	* It doesn't support realtime recovery.
+		With RAID you do not have to stop working when a disk fails.
+	* It's able to recover damages only from a single disk.
+		With a Backup you are able to recover from a complete
+		failure of the whole disk array.
+
+Getting Started
+	To use SnapRAID you need first to mount all the disks of your disk
+	array and select which one to dedicate as redundancy information.
+
+	This disk will be dedicated to this pourpuse only, and you should
+	not store any other data on it.
+
+	You have to pick the biggest disk in the array, as the redundancy
+	information may grow in size as the biggest data disk in the array.
+
+	Suppose now that you have mounted all your disks in the mount points:
+
+		:/mnt/diskpar
+		:/mnt/disk1
+		:/mnt/disk2
+		:/mnt/disk3
+
+	you have to create the configuration file /etc/snapraid.conf with
+	the following content:
+
+		:parity /mnt/diskpar/parity
+		:content /mnt/diskpar/content
+		:disk d1 /mnt/disk1/
+		:disk d2 /mnt/disk2/
+		:disk d3 /mnt/disk3/
+
+	At this point you are ready to start the "sync" command to build the
+	redundancy information.
+
+		:snapraid sync
+
+	This process will take some hours at best the first time, depending on
+	the size of the data already present in the data disks.
+	If the disks are empty the process is immediate.
+	You can stop it at any time pressing Ctrl+C, and at the next run it
+	will start where interrupted.
+
+	When this command completes, your data is SAFE.
+
+	At this point you can start using your data as you like, and peridiocally
+	update the redundancy information running the "sync" command.
+
+	To check the integrity of your data you can use the "check" command:
+
+		:snapraid check
+
+	If will read all your data, to check if it's correct.
+
+	If an error is found, you can use the "fix" command to fix it.
+
+		:snapraid fix
+
+	Note that the fix command will revert your data at the state of the
+	last "sync" command executed. It works like a snapshot was taken
+	in "sync".
+
+Configuration
+	SnapRAID requires a configuration file to know where your disk array
+	is located, and where storing the redundancy information.
+
+	This configuration file is located in /etc/snapraid.conf and
+	it should contains the following options:
+
+	=parity FILE
+		Defines the file to use to store the redundancy information.
+		It must be placed in a disk dedicated for this porpose with
+		as much free space as the biggest disk in the array.
+		This option can be used only one time.
+
+	=content FILE
+		Defines the file to use to store the content of the redundancy
+		organization.
+		It must be placed in the same disk of the parity file, or in
+		another location, but not in a disk of the array.
+		This option can be used only one time.
+
+	=disk NAME DIR
+		Defines the name and the mount point of the disks of the array.
+		NAME is used to identify the disk, and it must be unique.
+		DIR is the mount point of the disk in the filesystem.
+		You can change the mount point as you like, as far you
+		keep the NAME fixed.
+		You should use one option for each disk of the array.
+
+	=block_size SIZE_IN_KILOBYTES
+		Defines the basic block size in kilo bytes of
+		the redundancy blocks. The default is 128 and it should
+		work for most conditions.
+		You should use this option only if you do not have enough
+		memory to run SnapRAID.
+		It requires to run TS*24/BS bytes, where TS is the total
+		size in bytes of your disk array, and BS is the block size
+		in bytes.
+
+		For example with 6 disk of 2 TB and a block size of 128 kB you
+		have:
+
+			:memory = (6 * 2 * 2^40) * 24 / (128 * 2^10) = 2.3 GB
+
+	An example of a typical configuration is:
+
+		:parity /mnt/diskpar/parity
+		:content /mnt/diskpar/content
+		:disk d1 /mnt/disk1/
+		:disk d2 /mnt/disk2/
+		:disk d3 /mnt/disk3/
+		:block_size 256
+
+Commands
+	SnapRAID provides three simple commands that allow to:
+
+	* Make a backup/snapshot -> "sync"
+	* Check for integrity -> "check"
+	* Restore the last backup/snapshot -> "fix".
+	
+	=sync
+		Updates the redundancy information. All the modified files
+		in the disk array are read, and the redundancy data is
+		updated.
+		You can stop this process at any time pressing Ctrl+C,
+		without losing the work already done.
+
+	=check
+		Checks all the files the redundancy data. All the files
+		are hashed and compared with the snapshot saved in the
+		previous "sync" command.
+
+	=fix
+		Checks and fix all the files. It's like "check" but it
+		also tries to fix problems reverting the state of the
+		disk array at the previous "sync" command.
+
+Options
+	-c, --conf CONFIG
+		Selects the configuration file. If not specified is assumed
+		the file `/etc/snapraid.conf'.
+
+	-s, --start BLOCK
+		Starts the processing from the specified
+		block number. It could be useful to easy retry to fix
+		some specific block, in case of a damaged disk.
+
+	-f, --force
+		Forces insecure operations. If snapraid detects
+		an unsafe operation, it stops the execution asking you
+		to use this option to force the operation.
+		For example, it happens if all the files in a disk are
+		missing.
+
+	-e, --exclude PATTERN
+		This option define an exclusion pattern to be applyed at
+		the files with the "sync" command. It has no effect with
+		other commands.
+
+	-v, --verboe
+		Prints more information in the processing.
+
+	-h, --help
+		Prints a short help screen.
+
+	-V, --version
+		Prints the program version.
+
+Copyright
+	This file is Copyright (C) 2011 Andrea Mazzoleni
+
+See Also
+	rsync(1)
+