Monday, May 8, 2017

RAID 1

Your manager asks you to implement a fault-tolerant disk solution on your server. You have two 3TB hard disks and two controllers, so you decide to implement RAID 1. After the installation, your manager asks you how much storage space is now available for storing data. What do you tell her?
 A. 3TB
 B. 4TB
 C. 6TB
 D. 12TB


RAID-1 Also called disk mirroring, RAID-1 uses two disks and writes a copy of the data to both disks, providing fault tolerance in the case of a single drive failure. 

RAID 1 is mirroring or duplexing (if two controllers are used). Requiring at least two drives, RAID 1 writes the same data to each drive. RAID 1 arrays have great fault tolerance, but because each drive contains the full file, they are about as fast as a single drive when writing. Read times are faster, though, because the controller can access both drives together.

Another option to consider is using multiple drives in a RAID array. This gives you redundancy, if one drive in the array fails your data is still on the other. This isn’t a replacement for taking regular backups but it 
does protect you against a drive failure. 
With RAID 1, the simplest configuration, two drives are mirrored. All data is written to both drives but read from one (which can give 
improved read performance as the data comes from whichever drive seeks to it first). Most distro installers will handle installing to a 
RAID array, but with RAID 1 you can also install to a single drive and add the second to create the array. RAID is handled by the Linux 
kernel, do not enable any RAID settings on your motherboard. 

Key stretching - explicação

Você pode fazer uma chave fraca se tornar mais forte ao executar múltiplos processos para a mesma chave. Por exemplo, você pode ter uma se...