| When using and operating a high availability server or | | | | In the past, it was a requirement that the server |
| system within an organisation, you need to consider | | | | hardware was powered off to replace the hard disk, |
| that there may be times when hardware fails and | | | | but hot swap drives and caddies have allowed the |
| the system may be offline. This is par for the course | | | | server to continue to operate whilst the data is |
| when it comes to computers. No system in 100% fail | | | | recovered. SCSI hot swap drives allow you to |
| safe as there are so many things that can go wrong. | | | | remove the faulty hard disk and insert a new one |
| One of the main issues that IT departments face is | | | | without having to power off any part of the server. |
| loss of data if a disk fails. A way to overcome this | | | | This allows the server to continue running whilst the |
| issue is to employ a level of RAID and use SCSI hot | | | | new disks is restored or repaired and made part of |
| swap disks. | | | | the RAID array. |
| Using RAID allows you to spread your data across | | | | Each major manufacturer of server hardware has a |
| many disk drives in the server. This process has | | | | slightly different implementation of the hot swap |
| several levels of complexity and redundancy and | | | | technology. The SCSI hard disk sits in a caddy or |
| allows you to recover information from a failed disk | | | | tray which is specific to each server brand. The SCSI |
| using parity information, written to different disks. A | | | | disk itself is sometimes independent to the server |
| little like an algebra sum, where 1 + a = 3 (a = 2), | | | | brand, and therefore any similar size SCSI disk can be |
| RAID allows the data to be recreated when the | | | | used. |
| faulty hard disk is replaced. The server still operates, | | | | So, to maintain server up time, data consistency, |
| but it has to work out the sums on its own, making | | | | redundancy and customer satisfaction, use a RAID |
| it slightly slower. | | | | array with hot swappable hard disks. |