Al been learning by mistakes, Always check your hardware and Dealing with ilo4 and Datto Device

Jerry has been clone daughter laptop and received the following Error Message:??????

Andy dealing with Secure boot and EFI bios, Trinity Rescue Disk Trinity

We discuses Raid this week:

Different between software and Hardware Raid

Mdadm is Linux Software RAID management tool

Raid 0 – Which has no redundancy require more than two disk. So data normally is split of blocks of 64k, the first block is written to disk 1 and section written to disk 1 and then third data written 1st disk and so. Used to create large disk volumes and is fast writing to disks.So if you are write 100mb data each drive is write 50mb at once compare 1 drive writing a 100mb. So twice as fast and reads twice as fast as both disk can find the data which is being requested. Also no storage space lost.

Raid 1 –  Require two disk same size. Each block of data is written to both drive. You lose half storage (so if you have 2 x 1TB disk you get 1TB virtual disk). Their is Hit of write speed as both disk need to confirm that data has been written to both disk, You may get a bit fast read speed as you have two heads seeking for data. You can tolrate one disk failing,

Raid 5 – mean you can get greater storage, but you always lose one disk for parity so let say you have 4 disk in array, 4 x 1TB your storage space you would get would be 3TB. Parity  is a equation, called exclusive xor. Let think of easiy way of doing, so data written on disk 1 is 2, Data on disk 2 = 4 and data on disk 3 = 5, So the parity is would be those number add together 11 and written to the 4 disk.  so if we ever lost of drive (1-3) we could work out the value ie if we lost disk, using the parity of 11, we could subtract the other value on disk 2 and 3 so 11 – 4 – 5 = 2. The data which was store on disk 1. So if you had a disk failure and request that data the raid controller can restructure your data and present in to you in degrade mode. This would be slower as the controller would need to do this every time you request data.

The parity is not store on one disk, so first it would store data a on disk 1 and data b on disk 2 and data c on disk 3. Parity on disk 4. next time the data a could be written on disk 2 and data b is written on disk 3 and data c on disk 4 and parity on disk 1 and so so.

RAID 6 – Is the same as RAID 5 but you have two disk for Parity. You need a minimum of 4 disks,

http://blog.open-e.com/how-does-raid-5-work/