Storage

Question 1

What is SAS Storage?

Answer 1

Serial Attached SCSI

• SATA drives are slower and have higher failure rates that SAS. SATA is mostly for desktop, SAS is for enterprise.
• SATA cables are limited to 1 metre in length and the data and power are separate whereas SAS cables can be up to 10 metres in length with power and data provided through the same cable.

Question 2

What are common RAID levels?

Answer 2

• RAID 0 - striping (fast, not fault tolerant)
• RAID 1 - mirroring (good but uses double the drives)
• RAID 5 - striping with parity (fast read, slow write)
• RAID 10 - striping and mirroring (fast rebuilds but still uses twice the drives).

Question 3

What is JBOD?

Answer 3

• “Just a Bunch of Drives”

Question 4

How are devices names (SCSI, SATA, etc…)?

Answer 4

First of all, all the devices populate the /dev folder.

Also, it is important to note that (E)IDE and PATA terms usually refer to the same thing, which is the interface standard PATA. IDE and PATA are interchangable terms in this context.

There was a major change in naming conventions for block devices in Linux, around the release of Linux kernel version 2.6. The kernel supports all ATA devices through libATA, which started with SATA devices support in 2003 and was extended to current PATA support.