Adds the -t option to limit the number of blocks processed.

More tests with incomplete sync.
2026-10-25 18:40:19 -04:00 · 2011-03-23 18:54:08 +01:00 · 2011-03-23 18:54:08 +01:00 · 87bb5c7a66
commit 87bb5c7a66
parent 25841deb04
9 changed files with 93 additions and 557 deletions
--- a/Makefile.am
+++ b/Makefile.am
@ -82,6 +82,17 @@ check-local:
 	$(TESTENV) ./mktest$(EXEEXT) generate 3 3 100 4000
 	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf sync
 	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf check
+	echo --- Delete some files and create some new, sync and check in multiple steps
+	rm test/disk1/4*
+	rm test/disk2/5*
+	rm test/disk2/6*
+	$(TESTENV) ./mktest$(EXEEXT) generate 4 3 100 4000
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf -t 7 sync
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf check
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf -t 11 sync
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf check
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf sync
+	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf check
 	echo --- Delete some files, fix and check
 	rm test/disk1/1*
 	$(TESTENV) ./snapraid$(EXEEXT) -c $(srcdir)/test.conf check 2>/dev/null
--- a/check.c
+++ b/check.c
@ -66,6 +66,7 @@ static int state_check_process(struct snapraid_state* state, int fix, int parity
 		struct snapraid_block* failed_block;
 		struct snapraid_handle* failed_handle;
 		int one_hash;
+		int all_parity;

 		/* for each disk */
 		one_hash = 0;
@ -73,6 +74,7 @@ static int state_check_process(struct snapraid_state* state, int fix, int parity
 			struct snapraid_block* block = disk_block_get(handle[j].disk, i);
 			if (block && bit_has(block->flag, BLOCK_HAS_HASH)) {
 				one_hash = 1;
+				break;
 			}
 		}

@ -83,10 +85,12 @@ static int state_check_process(struct snapraid_state* state, int fix, int parity
 		/* start with 0 */
 		memset(xor_buffer, 0, state->block_size);

-		/* for each disk, process the block */
-		failed = 0;
-		failed_block = 0;
+		all_parity = 1; /* if all hashed block have parity computed */
+		failed = 0; /* number of failed block */
+		failed_block = 0; /* last failed block */
 		failed_handle = 0;
+
+		/* for each disk, process the block */
 		for(j=0;j<diskmax;++j) {
 			int read_size;
 			struct md5_t md5;
@ -103,6 +107,10 @@ static int state_check_process(struct snapraid_state* state, int fix, int parity
 			if (!bit_has(block->flag, BLOCK_HAS_HASH))
 				continue;

+			/* keep track if at least one hashed block has no parity */
+			if (!bit_has(block->flag, BLOCK_HAS_PARITY))
+				all_parity = 0;
+
 			ret = handle_close_if_different(&handle[j], block->file);
 			if (ret == -1) {
 				fprintf(stderr, "WARNING! Without a working data disk, it isn't possible to fix errors on it.\n");
@ -170,7 +178,7 @@ static int state_check_process(struct snapraid_state* state, int fix, int parity
 			count_size += read_size;
 		}

-		if (parity_f == -1) {
+		if (parity_f == -1 || !all_parity) {
 			/* all the cases with no parity file */
 			if (failed != 0) {
 				fprintf(stderr, "%u: UNRECOVERABLE errors for this block\n", i);
@ -320,7 +328,7 @@ bail:
 	return 0;
 }

-void state_check(struct snapraid_state* state, int fix, block_off_t blockstart)
+void state_check(struct snapraid_state* state, int fix, block_off_t blockstart, block_off_t blockcount)
 {
 	char path[PATH_MAX];
 	block_off_t blockmax;
@ -342,6 +350,11 @@ void state_check(struct snapraid_state* state, int fix, block_off_t blockstart)
 		exit(EXIT_FAILURE);
 	}

+	/* adjust the number of block to process */
+	if (blockcount != 0 && blockstart + blockcount < blockmax) {
+		blockmax = blockstart + blockcount;
+	}
+
 	pathcpy(path, sizeof(path), state->parity);
 	if (fix) {
 		/* if fixing, create the file and open for writing */
--- a/snapraid.1
+++ b/snapraid.1
@ -2,13 +2,17 @@
 .SH NAME
 snapraid \(hy SnapRAID Backup For Disk Arrays
 .SH SYNOPSIS 
-snapraid [\(hyc, \(hy\(hyconf CONFIG] [\(hys, \(hy\(hystart BLOCK]
+snapraid [\(hyc, \(hy\(hyconf CONFIG]
 .PD 0
 .PP
 .PD
 	[\(hyZ, \(hy\(hyforce\(hyzero] [\(hyE, \(hy\(hyforce\(hyempty]
 .PD 0
 .PP
+.PD
+	[\(hys, \(hy\(hystart BLKSTART] [\(hyt, \(hy\(hycount BLKCOUNT]
+.PD 0
+.PP
 .PD
 	[\(hyv, \(hy\(hyverbose]
 .PD 0
@ -237,11 +241,6 @@ Selects the configuration file. If not specified is assumed
 the file \(cq/etc/snapraid.conf\(cq in Unix, and \(cqsnapraid.conf\(cq
 in Windows.
 .TP
-.B \(hys, \(hy\(hystart BLOCK
-Starts the processing from the specified
-block number. It could be useful to easy retry to check or
-fix some specific block, in case of a damaged disk.
-.TP
 .B \(hyZ, \(hy\(hyforce\(hyzero
 Forces the insecure operation of syncing a file with zero
 size that before was not empty.
@ -258,6 +257,15 @@ unless you specify this option.
 This allows to easily detect when a data file\(hysystem is not
 mounted.
 .TP
+.B \(hys, \(hy\(hystart BLKSTART
+Starts the processing from the specified
+block number. It could be useful to easy retry to check
+or fix some specific block, in case of a damaged disk.
+.TP
+.B \(hyt, \(hy\(hycount BLKCOUNT
+Process only the specified number of blocks.
+It\(cqs present mainly for testing.
+.TP
 .B \(hyv, \(hy\(hyverbose
 Prints more information in the processing.
 .TP
--- a/snapraid.c
+++ b/snapraid.c
@ -43,19 +43,21 @@ void usage(void) {
 	printf("Usage: " PACKAGE " [options]\n");
 	printf("\n");
 	printf("Options:\n");
-	printf("  " SWITCH_GETOPT_LONG("-c, --conf FILE    ", "-c") "  Configuration file (default " CONF ")\n");
-	printf("  " SWITCH_GETOPT_LONG("-s, --start BLK    ", "-s") "  Start from the specified block number\n");
-	printf("  " SWITCH_GETOPT_LONG("-Z, --force-zero   ", "-Z") "  Force synching of files that get zero size\n");
-	printf("  " SWITCH_GETOPT_LONG("-E, --force-empty  ", "-E") "  Force synching of disks that get empty\n");
-	printf("  " SWITCH_GETOPT_LONG("-v, --verbose      ", "-v") "  Verbose\n");
-	printf("  " SWITCH_GETOPT_LONG("-h, --help         ", "-h") "  Help\n");
-	printf("  " SWITCH_GETOPT_LONG("-V, --version      ", "-V") "  Version\n");
+	printf("  " SWITCH_GETOPT_LONG("-c, --conf FILE     ", "-c") "  Configuration file (default " CONF ")\n");
+	printf("  " SWITCH_GETOPT_LONG("-s, --start BLKSTART", "-s") "  Start from the specified block number\n");
+	printf("  " SWITCH_GETOPT_LONG("-t, --count BLKCOUNT", "-t") "  Count of block to process\n");
+	printf("  " SWITCH_GETOPT_LONG("-Z, --force-zero    ", "-Z") "  Force synching of files that get zero size\n");
+	printf("  " SWITCH_GETOPT_LONG("-E, --force-empty   ", "-E") "  Force synching of disks that get empty\n");
+	printf("  " SWITCH_GETOPT_LONG("-v, --verbose       ", "-v") "  Verbose\n");
+	printf("  " SWITCH_GETOPT_LONG("-h, --help          ", "-h") "  Help\n");
+	printf("  " SWITCH_GETOPT_LONG("-V, --version       ", "-V") "  Version\n");
 }

 #if HAVE_GETOPT_LONG
 struct option long_options[] = {
 	{ "conf", 1, 0, 'c' },
 	{ "start", 1, 0, 's' },
+	{ "count", 1, 0, 't' },
 	{ "force-zero", 0, 0, 'Z' },
 	{ "force-empty", 0, 0, 'E' },
 	{ "verbose", 0, 0, 'v' },
@ -65,7 +67,7 @@ struct option long_options[] = {
 };
 #endif

-#define OPTIONS "c:s:ZEvhV"
+#define OPTIONS "c:s:t:ZEvhV"

 volatile int global_interrupt = 0;

@ -92,6 +94,7 @@ int main(int argc, char* argv[])
 	struct snapraid_state state;
 	int operation;
 	block_off_t blockstart;
+	block_off_t blockcount;
 	int ret;

 	/* intercept Ctrl+C */
@ -103,6 +106,7 @@ int main(int argc, char* argv[])
 	force_zero = 0;
 	force_empty = 0;
 	blockstart = 0;
+	blockcount = 0;

 	opterr = 0;
 	while ((c =
@ -122,6 +126,12 @@ int main(int argc, char* argv[])
 				exit(EXIT_FAILURE);
 			}
 			break;
+		case 't' :
+			if (stru32(optarg, &blockcount) != 0) {
+				fprintf(stderr, "Invalid count number '%s'\n", optarg);
+				exit(EXIT_FAILURE);
+			}
+			break;
 		case 'Z' :
 			force_zero = 1;
 			break;
@ -168,7 +178,7 @@ int main(int argc, char* argv[])

 		state_scan(&state);

-		ret = state_sync(&state, blockstart);
+		ret = state_sync(&state, blockstart, blockcount);

 		/* save the new state if required */
 		if (state.need_write)
@ -180,7 +190,7 @@ int main(int argc, char* argv[])
 	} else {
 		state_read(&state);

-		state_check(&state, operation == OPERATION_FIX, blockstart);
+		state_check(&state, operation == OPERATION_FIX, blockstart, blockcount);
 	}

 	state_done(&state);
--- a/snapraid.d
+++ b/snapraid.d
@ -2,8 +2,9 @@ Name{number}
 	snapraid - SnapRAID Backup For Disk Arrays

 Synopsis
-	:snapraid [-c, --conf CONFIG] [-s, --start BLOCK]
+	:snapraid [-c, --conf CONFIG]
 	:	[-Z, --force-zero] [-E, --force-empty]
+	:	[-s, --start BLKSTART] [-t, --count BLKCOUNT]
 	:	[-v, --verbose]
 	:	COMMAND

@ -155,11 +156,6 @@ Options
 		the file '/etc/snapraid.conf' in Unix, and 'snapraid.conf' 
 		in Windows.

-	-s, --start BLOCK
-		Starts the processing from the specified
-		block number. It could be useful to easy retry to check or
-		fix some specific block, in case of a damaged disk.
-
 	-Z, --force-zero
 		Forces the insecure operation of syncing a file with zero
 		size that before was not empty.
@ -176,6 +172,15 @@ Options
 		This allows to easily detect when a data file-system is not
 		mounted.

+	-s, --start BLKSTART
+		Starts the processing from the specified
+		block number. It could be useful to easy retry to check
+		or fix some specific block, in case of a damaged disk.
+
+	-t, --count BLKCOUNT
+		Process only the specified number of blocks.
+		It's present mainly for testing.
+
 	-v, --verbose
 		Prints more information in the processing.

--- a/snapraid.html
+++ b/snapraid.html
@ -1,521 +0,0 @@
-<html>
-<head>
-<title>SnapRAID Backup For Disk Arrays</title>
-</head>
-<body>
-<center><h2>SnapRAID Backup For Disk Arrays</h2></center>
-<h2><a name="1">1</a> 
-Synopsis
-</h2>
-<pre>
-snapraid [-c, --conf CONFIG] [-s, --start BLOCK]
-&nbsp;&nbsp;&nbsp;&nbsp;[-Z, --force-zero] [-E, --force-empty]
-&nbsp;&nbsp;&nbsp;&nbsp;[-v, --verbose]
-&nbsp;&nbsp;&nbsp;&nbsp;COMMAND
-</pre>
-<p>
-<pre>
-snapraid [-V, --version] [-h, --help]
-</pre>
-<h2><a name="2">2</a> 
-Description
-</h2>
-SnapRAID is a backup program for a disk array using redundancy.
-<p>
-SnapRAID uses a disk of the array to store redundancy information,
-and it allows to recover from a disk failure.
-<p>
-SnapRAID is mainly targeted for a home media center, where you have
-a lot of big files that rarely change.
-<p>
-The main features of SnapRAID are:
-<ul>
-<li>
-You can start using SnapRAID with already filled disks.
-</li>
-<li>
-The disks of the array can have different sizes.
-</li>
-<li>
-You can add more disks at the array at any time.
-</li>
-<li>
-If you accidentally delete some files in a disk, you can
-recover them.
-</li>
-<li>
-If more than one disk fails, you lose the data only on the
-failed disks. All the data in the other disks is safe.
-</li>
-<li>
-It doesn't lock-in your data. You can stop using SnapRAID at any
-time without the need to reformat or move data.
-</li>
-<li>
-All your data is hashed to ensure data integrity.
-</li>
-</ul>
-<p>
-The official site of SnapRAID is:
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-<a href="http://snapraid.sourceforge.net">http://snapraid.sourceforge.net</a>
-</pre>
-</td></tr></table>
-<h2><a name="3">3</a> 
-Limitations
-</h2>
-SnapRAID is in between a RAID and a backup program trying to get the best
-benefits of them. Altought it also has some limitations that you should
-consider before using it.
-<p>
-The main one, is that if a disk fail, and you haven't recently synched,
-you may not able to do a complete recover.
-More specifically, you may be unable to recover up to the size of the
-amount of the changed or deleted files, from the last sync operation.
-This happens even if the files changed or deleted are not in the
-failed disk.
-New added files don't prevent the recovering of the already existing
-files. You may only lose the just added files, if they were on the failed
-disk.
-<p>
-This is the reason because SnapRAID is better suited for data that
-rarely change.
-<p>
-Other limitations are:
-* You have different filesystems for each disk.
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-Using a RAID you have only a big filesystem.
-</td></tr></table>
-<ul>
-<li>
-It doesn't stripe data.
-With RAID you get a speed boost with striping.
-</li>
-<li>
-It doesn't support realtime recovery.
-With RAID you do not have to stop working when a disk fails.
-</li>
-<li>
-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.
-</li>
-</ul>
-<h2><a name="4">4</a> 
-Getting Started
-</h2>
-To use SnapRAID you need first select one disk of your disk array
-to dedicate at the redundancy information.
-<p>
-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.
-<p>
-This disk will be dedicated to this pourpuse only and you should
-not store other data on it.
-<p>
-Suppose now that you have mounted all your disks in the mount points:
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-/mnt/diskpar &lt;- selected disk for parity
-/mnt/disk1
-/mnt/disk2
-/mnt/disk3
-</pre>
-</td></tr></table>
-<p>
-you have to create the configuration file /etc/snapraid.conf with
-the following content:
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-parity /mnt/diskpar/parity
-content /mnt/diskpar/content
-disk d1 /mnt/disk1/
-disk d2 /mnt/disk2/
-disk d3 /mnt/disk3/
-</pre>
-</td></tr></table>
-<p>
-At this point you are ready to start the "sync" command to build the
-redundancy information.
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-snapraid sync
-</pre>
-</td></tr></table>
-<p>
-This process maty take some hours the first time, depending on the size
-of the data already present in the disks. If the disks are empty
-the process is immediate.
-<p>
-You can stop it at any time pressing Ctrl+C, and at the next run it
-will start where interrupted.
-<p>
-When this command completes, your data is SAFE.
-<p>
-At this point you can start using your data as you like, and peridiocally
-update the redundancy information running the "sync" command.
-<p>
-To check the integrity of your data you can use the "check" command:
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-snapraid check
-</pre>
-</td></tr></table>
-<p>
-If will read all your data, to check if it's correct.
-<p>
-If an error is found, you can use the "fix" command to fix it.
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-snapraid fix
-</pre>
-</td></tr></table>
-<p>
-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".
-<p>
-In this regard snapraid is more like a backup program than a RAID
-system. For example, you can use it to recover from an accidentally
-deleted directory, simply running the fix command.
-<h2><a name="5">5</a> 
-Commands
-</h2>
-SnapRAID provides three simple commands that allow to:
-<ul>
-<li>
-Make a backup/snapshot -&gt; "sync"
-</li>
-<li>
-Check for integrity -&gt; "check"
-</li>
-<li>
-Restore the last backup/snapshot -&gt; "fix".
-</li>
-</ul>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-sync
-</strong></td></tr><tr><td>
-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.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-check
-</strong></td></tr><tr><td>
-Checks all the files the redundancy data. All the files
-are hashed and compared with the snapshot saved in the
-previous "sync" command.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-fix
-</strong></td></tr><tr><td>
-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.
-</td></tr>
-</table>
-<h2><a name="6">6</a> 
-Options
-</h2>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-c, --conf CONFIG
-</strong></td></tr><tr><td>
-Selects the configuration file. If not specified is assumed
-the file `/etc/snapraid.conf'.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-s, --start BLOCK
-</strong></td></tr><tr><td>
-Starts the processing from the specified
-block number. It could be useful to easy retry to check or
-fix some specific block, in case of a damaged disk.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-Z, --force-zero
-</strong></td></tr><tr><td>
-Forces the insecure operation of synching a file with zero
-size that before was not empty.
-If SnapRAID detects such condition, it stops proceeding
-unless you specify this option.
-This allows to easily detect when after a system crash,
-some accessed files were zeroed.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-E, --force-empty
-</strong></td></tr><tr><td>
-Forces the insecure operation of synching an empty disk
-that before was not empty.
-If SnapRAID detects such condition, it stops proceeding
-unless you specify this option.
-This allows to easily detect when a data filesystem is not
-mounted.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-v, --verbose
-</strong></td></tr><tr><td>
-Prints more information in the processing.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-h, --help
-</strong></td></tr><tr><td>
-Prints a short help screen.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-V, --version
-</strong></td></tr><tr><td>
-Prints the program version.
-</td></tr>
-</table>
-<h2><a name="7">7</a> 
-Configuration
-</h2>
-SnapRAID requires a configuration file to know where your disk array
-is located, and where storing the redundancy information.
-<p>
-This configuration file is located in /etc/snapraid.conf and
-it should contains the following options:
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-parity FILE
-</strong></td></tr><tr><td>
-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.
-Leaving the parity disk reserved for only this file, ensures that
-it doesn't get fragmented, improving the performance.
-This option can be used only one time.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-content FILE
-</strong></td></tr><tr><td>
-Defines the file to use to store the content of the redundancy
-organization.
-It can be placed in the same disk of the parity file, or better
-in another disk, but NOT in a data disk of the array.
-This option can be used only one time.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-disk NAME DIR
-</strong></td></tr><tr><td>
-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.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-exclude PATTERN
-</strong></td></tr><tr><td>
-Defines the file or directory patterns to exclude from the sync
-process. See the PATTERN section for more details in the
-pattern specifications.
-This option can be used many times.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-block_size SIZE_IN_KIBIBYTES
-</strong></td></tr><tr><td>
-Defines the basic block size in kibi bytes of
-the redundancy blocks. Where one kibi bytes is 1024 bytes.
-The default is 256 and it should work for most conditions.
-You increase this value if you do not have enough memory
-to run SnapRAID.
-It requires to run something about TS*24/BS bytes, where TS
-is the total size in bytes of your disk array, and BS is the
-block size in bytes.
-</td></tr>
-</table>
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-For example with 6 disk of 2 TiB and a block size of 256 KiB
-(1 KiB = 1024 Bytes) you have:
-</td></tr></table>
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-memory = (6 * 2 * 2^40) * 24 / (256 * 2^10) = 1.1 GiB
-</pre>
-</td></tr></table>
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-You should instead decrease this value if you have a lot of
-small files in the disk array. For each file, even if of few
-bytes, a whole block is always allocated, so you may have a lot
-of unused space.
-</td></tr></table>
-<p>
-An example of a typical configuration is:
-<p>
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-parity /mnt/diskpar/parity
-content /mnt/diskpar/content
-disk d1 /mnt/disk1/
-disk d2 /mnt/disk2/
-disk d3 /mnt/disk3/
-exclude *.bak
-exclude /lost+found/
-exclude tmp/
-block_size 256
-</pre>
-</td></tr></table>
-<h2><a name="8">8</a> 
-Pattern
-</h2>
-Patterns are used to define the files and directories to exclude
-from the redundancy process.
-<p>
-It makes sense to exclude any file not worth to be saved or that
-changes often.
-<p>
-There are four different types of patterns:
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-FILE
-</strong></td></tr><tr><td>
-Excludes any file named as FILE. You can use any globbing
-character like * and ?.
-This pattern is applied only to files and not to directories.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-DIR/
-</strong></td></tr><tr><td>
-Excludes any directory named DIR. You can use any globbing
-character like * and ?.
-This pattern is applied only to directories and not to files.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-/PATH/FILE
-</strong></td></tr><tr><td>
-Excludes the exact specified file path. You can use any
-globbing character like * and ? but they never matches a
-directory slash.
-This pattern is applied only to files and not to directories.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-/PATH/DIR/
-</strong></td></tr><tr><td>
-Excludes the exact specified directory path. You can use any
-globbing character like * and ? but they never matches a
-directory slash.
-This pattern is applied only to directories and not to files.
-</td></tr>
-</table>
-<p>
-For example:
-<table width="100%" border="0" cellspacing="0" cellpadding="2"><tr><td width="5%"></td><td width="95%">
-<pre>
-# Excludes any file named "*.bak"
-exclude *.bak
-# Excludes the root directory "/lost+found"
-exclude /lost+found/
-# Excludes any directory named "tmp"
-exclude tmp/
-</pre>
-</td></tr></table>
-<h2><a name="9">9</a> 
-Content
-</h2>
-SnapRAID creates a content file describing the content of your disk array.
-<p>
-You should never change it manually, altought the format of this file is
-described here.
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-blk_size SIZE
-</strong></td></tr><tr><td>
-Defines the size of the block in bytes. It must match the size
-defined in the configuration file.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-file DISK SIZE TIME INODE PATH
-</strong></td></tr><tr><td>
-Defines a file in the specified DISK.
-The INODE number is used to identify the file in the "sync"
-command, allowing to rename or move the file in disk without
-the need to recompute the parity for it.
-The SIZE and TIME information are used to identify if the file
-changed from the last "sync" command, and if there is the need
-to recompute the parity.
-The PATH information is used in the "check" and "fix" commands
-to identify the file.
-</td></tr>
-</table>
-<table width="100%" border="0" cellspacing="0" cellpadding="2">
-<tr valign="top" align="left"><td><strong>
-blk BLOCK HASH
-</strong></td></tr><tr><td>
-Defines the ordered parity block list used by the last defined file.
-BLOCK is the block position in the "parity" file.
-0 for the first block, 1 for the second one and so on.
-HASH is the md5 of the block. In the last block of the file,
-the HASH is the hash of only the used part of the block.
-</td></tr>
-</table>
-<h2><a name="10">10</a> 
-Parity
-</h2>
-SnapRAID creates a parity file containing the parity information of your disk array.
-<p>
-It's a binary file, containing the parity information of all the blocks defined
-in the "content" file.
-<p>
-For all the blocks at a given position, the parity information is computed with
-the XOR operator applied to all the blocks.
-<p>
-When a file block is shorter than the default block size, for example because it's
-the last block of a file, it's assumed filled with 0 at the end in the XOR operation.
-<h2><a name="11">11</a> 
-Copyright
-</h2>
-This file is Copyright (C) 2011 Andrea Mazzoleni
-<h2><a name="12">12</a> 
-See Also
-</h2>
-rsync(1)
-</body>
-</html>
--- a/snapraid.txt
+++ b/snapraid.txt
@ -6,8 +6,9 @@
 1 SYNOPSIS
 ==========

-snapraid [-c, --conf CONFIG] [-s, --start BLOCK]
+snapraid [-c, --conf CONFIG]
 	[-Z, --force-zero] [-E, --force-empty]
+	[-s, --start BLKSTART] [-t, --count BLKCOUNT]
 	[-v, --verbose]
 	COMMAND

@ -174,11 +175,6 @@ SnapRAID provides three simple commands that allow to:
        the file '/etc/snapraid.conf' in Unix, and 'snapraid.conf'
        in Windows.

-    -s, --start BLOCK
-        Starts the processing from the specified
-        block number. It could be useful to easy retry to check or
-        fix some specific block, in case of a damaged disk.
-
    -Z, --force-zero
        Forces the insecure operation of syncing a file with zero
        size that before was not empty.
@ -195,6 +191,15 @@ SnapRAID provides three simple commands that allow to:
        This allows to easily detect when a data file-system is not
        mounted.

+    -s, --start BLKSTART
+        Starts the processing from the specified
+        block number. It could be useful to easy retry to check
+        or fix some specific block, in case of a damaged disk.
+
+    -t, --count BLKCOUNT
+        Process only the specified number of blocks.
+        It's present mainly for testing.
+
    -v, --verbose
        Prints more information in the processing.

--- a/state.h
+++ b/state.h
@ -71,12 +71,12 @@ void state_scan(struct snapraid_state* state);
 /**
 * Syncs the parity data.
 */
-int state_sync(struct snapraid_state* state, block_off_t blockstart);
+int state_sync(struct snapraid_state* state, block_off_t blockstart, block_off_t blockcount);

 /**
 * Checks (and fixes) all the files and the parity data.
 */
-void state_check(struct snapraid_state* state, int fix, block_off_t blockstart);
+void state_check(struct snapraid_state* state, int fix, block_off_t blockstart, block_off_t blockcount);

 /**
 * Writes the progress.
--- a/sync.c
+++ b/sync.c
@ -217,7 +217,7 @@ bail:
 	return 0;
 }

-int state_sync(struct snapraid_state* state, block_off_t blockstart)
+int state_sync(struct snapraid_state* state, block_off_t blockstart, block_off_t blockcount)
 {
 	char path[PATH_MAX];
 	block_off_t blockmax;
@ -236,6 +236,11 @@ int state_sync(struct snapraid_state* state, block_off_t blockstart)
 		fprintf(stderr, "Error in the starting block %u. It's bigger than the parity size %u.\n", blockstart, blockmax);
 		exit(EXIT_FAILURE);
 	}
+	
+	/* adjust the number of block to process */
+	if (blockcount != 0 && blockstart + blockcount < blockmax) {
+		blockmax = blockstart + blockcount;
+	}

 	pathcpy(path, sizeof(path), state->parity);
 	f = parity_create(path, size);