Definition of RAID Redundant Array of Independent Disks Combine multiple physical disks into one logical unit so to increase read/write performance or data redundancy. Is NOT a reliable backup plan Confidential
RAID levels Confidential Level Descriptio n Min # of drives** Space Efficiency Fault Tolerance Read Benefit Write Benefit Image RAID 0 Block-level striping without parity or mirroring. 21nonenX RAID 1 Mirroring without parity or striping. 21/n n1 drives nX1X *Extract from http://en.wikipedia.org/wiki/RAID
Other RAID levels LevelDescription Min # of drives** Space Efficiency Fault Tolerance Array Failure Rate*** Read Benefit Write BenefitImage RAID 2 Bit-level striping with dedicated Hamming- code parity. 3 1 1/n log 2 (n-1) can recover from 1 drive failure or repair corrupt data or parity variable RAID 3 Byte-level striping with dedicated parity. 31 1/n1 driven(n1)r 2 (n1)X(n1)X* RAID 4 Block-level striping with dedicated parity. 31 1/n1 driven(n1)r 2 (n1)X(n1)X* RAID 5 Block-level striping with distributed parity. 31 1/n1 driven(n1)r 2 (n1)X* RAID 6 Block-level striping with double distributed parity. 41 2/n2 drives n(n-1)(n- 2)r 3 (n2)X* Confidential * Assumes hardware is fast enough to support ** Assumes a non-degenerate minimum number of drives ***Assumes independent, identical rate of failure amongst drives
Hardware RAID RAID controller card - usually a PCIe expansion card - calculations are done by the controller (no CPU resource is needed) - high price - thermal/power issue Intel I/O Controller Hub(ICH) - come with the computer but not all ICH supports RAID - V2616 uses ICH9M-SFF, which supports RAID 0,1 Confidential
Software RAID Done by OS, no extra hardware is required Uses CPU resourceperformance depends greatly on CPU speed Free tool on Linux: mdadm Confidential
Using mdadm to configure RAID 0 on V2400 series Confidential
Install mdadm the root file system is set to be read-only, change to read-write: #mount –o remount,rw / use apt-get install command to install mdadm #apt-get install mdadm * what is apt? Appendix A Confidential
Package configuration window will appear, select Ok and click Enter Confidential
Use the default setting. Select Ok and click Enter Confidential
Insert USB disks USB devices will be mounted automatically. You may use the following command can to check the filesystem: #df –h Confidential the usb devices are mounted here
Create RAID device unmount the USB devices first #umount /dev/sdb1 #umount /dev/sdc1 create RAID device #mdadm --create /dev/md0 --level=0 --raid- devices=2 /dev/sdb /dev/sdc Confidential
Create RAID device Check the RAID device: #mdadm --detail /dev/md0 Confidential RAID level is 0
Create RAID device Formate the disk #mkfs -t ext3 /dev/md0 Confidential
Create RAID device mount the device somewhere you want #mkdir /home/raid_disk #mount /dev/md0 /home/raid_disk use df command to check the filesysytem again Confidential the usb devices became /dev/md0, with the disk size of 15G and is mounted to assigned path
Auto-mount the RAID device edit /etc/rc.local like below, the script here will be executed after boot. try reboot the computer with modified and unmodified rc.local and see if /dev/md0 is mounted correctly. Confidential add this line
Appendix A: what is apt? Advanced Packaging tool used on Debian linux distribution to handle installation and removal of software packages. Important files and commands: /etc/apt/sources.list : Locations to fetch packages from. If your cannot fetch the package, you may want to check if the sources list is still valid. apt-get install package_name : install package_name apt-cache search text : Find package relate to text Confidential
Configure RAID 0 on V2616 Using Intel Rapid Storage Technology Confidential
V2616 RAID Function Configuration The V2616 computers have two storage trays that allow users to install two 2.5-inch SATA hard disks, and support RAID 0 and RAID 1 functions for data backup and recovery. Before using the RAID functions, you need to install two SATA hard disks with the same capacity in the V2616 computer.
1. Check disk management, right-click on the two disks to initialize. Configuring RAID 0 Function
2. Launch the Intel Rapid Storage Technology program
3. Press Create button, select Optimized disk performance (RAID 0) option, and then click Next.
4. Use the following settings to save the data to another disk. a. Select the disks installed on the computer. b. Specify the volume size by adjusting the scroll bar. c. Determine the data strip size. d. Check Enable volume write-back cache. a b c d
5. Confirm the settings and then click Create Volume.
8. Check Disk Management. Right-click on the disk to initialize disk, and then click OK.
9. Right-click on the disk to use New Simple Volume Wizard. Click Next to continue.
10. Enter the partition size in the blank, and then click Next to continue.
11. Select Assign the following drive letter, and then click Next to continue.
12. Select Format this partition with the following settings. a. File system: NTFT. b. Allocation unit size: Default. c. Volume label: New Volume (the default value). d. Check Perform a quick format. a b c d
13. Click Finish to close the New Partition Wizard.
14. When finished, you may check the disk status from Disk Management column.