RAID 01, also called RAID 0+1, is a RAID level using a mirror of stripes, achieving both replication and sharing of data between disks.[3] The usable capacity of a RAID 01 array is the same as in a RAID 1 array made of the same drives, in which one half of the drives is used to mirror the other half. (N/2) \cdot S_{\mathrm{min}}, where N is the total number of drives and S_{\mathrm{min}} is the capacity of the smallest drive in the array.[4]

At least four disks are required in a standard RAID 01 configuration, but larger arrays are also used. 

RAID 10, also called RAID 1+0 and sometimes RAID 1&0, is similar to RAID 01 with an exception that two used standard RAID levels are layered in the opposite order; thus, RAID 10 is a stripe of mirrors.[3]

RAID 10, as recognized by the storage industry association and as generally implemented by RAID controllers, is a RAID 0 array of mirrors, which may be two- or three-way mirrors,[6] and requires a minimum of four drives. However, a nonstandard definition of "RAID 10" was created for the Linux MD driver;[7] Linux "RAID 10" can be implemented with as few as two disks. Implementations supporting two disks such as Linux RAID 10 offer a choice of layouts.[7] Arrays of more than four disks are also possible.

According to manufacturer specifications and official independent benchmarks,[8][9][10] in most cases RAID 10 provides better throughput and latency than all other RAID levels except RAID 0 (which wins in throughput). Thus, it is the preferable RAID level for I/O-intensive applications such as database, email, and web servers, as well as for any other use requiring high disk performance.[11] 

sarang> wget http://www.xen.dds.nl/f/scripts/extundelete

--2015-12-27 12:34:28--  http://www.xen.dds.nl/f/scripts/extundelete

Resolving www.xen.dds.nl... 85.17.251.154

Connecting to www.xen.dds.nl|85.17.251.154|:80... connected.

HTTP request sent, awaiting response... 200 OK

Length: 633541 (619K) [text/plain]

Saving to: 'extundelete'

100%[======================================>] 633,541      198KB/s   in 3.1s

2015-12-27 12:34:32 (198 KB/s) - 'extundelete' saved [633541/633541]

sarang> ./extundelete

No action specified; implying --superblock.

./extundelete: Missing device name.

Usage: ./extundelete [options] [--] device-file

Options:

  --version, -[vV]       Print version and exit successfully.

  --help,                Print this help and exit successfully.

  --superblock           Print contents of superblock in addition to the rest.

                         If no action is specified then this option is implied.

  --journal              Show content of journal.

  --after dtime          Only process entries deleted on or after 'dtime'.

  --before dtime         Only process entries deleted before 'dtime'.

Actions:

  --inode ino            Show info on inode 'ino'.

  --block blk            Show info on block 'blk'.

  --restore-inode ino[,ino,...]

                         Restore the file(s) with known inode number 'ino'.

                         The restored files are created in ./RECOVERED_FILES

                         with their inode number as extension (ie, file.12345).

  --restore-file 'path'  Will restore file 'path'. 'path' is relative to root

                         of the partition and does not start with a '/'

                         The restored file is created in the current

                         directory as 'RECOVERED_FILES/path'.

  --restore-files 'path' Will restore files which are listed in the file 'path'.

                         Each filename should be in the same format as an option

                         to --restore-file, and there should be one per line.

  --restore-directory 'path'

                         Will restore directory 'path'. 'path' is relative to the

                         root directory of the file system.  The restored

                         directory is created in the output directory as 'path'.

  --restore-all          Attempts to restore everything.

  -j journal             Reads an external journal from the named file.

  -b blocknumber         Uses the backup superblock at blocknumber when opening

                         the file system.

  -B blocksize           Uses blocksize as the block size when opening the file

                         system.  The number should be the number of bytes.

  --log 0                Make the program silent.

  --log filename         Logs all messages to filename.

--log D1=0,D2=filename   Custom control of log messages with comma-separated

   Examples below:       list of options.  Dn must be one of info, warn, or

   --log info,error      error.  Omission of the '=name' results in messages

   --log warn=0          with the specified level to be logged to the console.

   --log error=filename  If the parameter is '=0', logging for the specified

                         level will be turned off.  If the parameter is

                         '=filename', messages with that level will be written

                         to filename.

   -o directory          Save the recovered files to the named directory.

                         The restored files are created in a directory

                         named 'RECOVERED_FILES/' by default.

./extundelete: Error parsing command-line options. 

sarang> mount

/dev/root on / type ext4 (defaults)

/sys on /sys type sysfs (0)

none on /dev/pts type devpts (gid=4,mode=620)

/tmp on /tmp type tmpfs (0)

/run on /run type tmpfs (rw,nosuid,nodev,relatime,mode=755)

/dev/shm on /dev/shm type tmpfs (rw,nosuid,nodev,relatime)

/proc/bus/usb on /proc/bus/usb type usbfs (0)

/dev/vg1001/lv on /volume2 type ext4 (usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0,synoacl)

/dev/vg1000/lv on /volume1 type ext4 (usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0,synoacl)

securityfs on /sys/kernel/security type securityfs (0)

/dev/sdq1 on /volumeUSB1/usbshare type fuseblk (rw,allow_other,blksize=4096,default_permissions) 

sarang> ./extundelete /dev/vg1001/lv --restore-all

NOTICE: Extended attributes are not restored.

WARNING: EXT3_FEATURE_INCOMPAT_RECOVER is set.

The partition should be unmounted to undelete any files without further data loss.

If the partition is not currently mounted, this message indicates

it was improperly unmounted, and you should run fsck before continuing.

If you decide to continue, extundelete may overwrite some of the deleted

files and make recovering those files impossible.  You should unmount the

file system and check it with fsck before using extundelete.

Would you like to continue? (y/n)

y

Loading filesystem metadata ... 14868 groups loaded.

Loading journal descriptors ... 30303 descriptors loaded.

Searching for recoverable inodes in directory / ...

1119 recoverable inodes found.

Looking through the directory structure for deleted files ...

Unable to restore inode 30802326 (@tmp/pkglist.tmp/synoserver.krn.W5eobS): Space has been reallocated.

Unable to restore inode 62128599 (delete.zip): Space has been reallocated.

Unable to restore inode 62128600 (lost+found/synoserver.enu): Space has been reallocated.

3 recoverable inodes still lost. 

sarang> ls -al

drwx--x--x    4 admin    users         4096 Dec 27 12:42 .

drwx--x--x    7 root     root          4096 Oct 12 10:20 ..

drwx--x--x    5 root     root          4096 Dec 27 12:50 RECOVERED_FILES

-rwx--x--x    1 admin    users       633541 Mar  3  2015 extundelete