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FlashDisk RAID User-Friendly Interfaces

Introduction
FlashDisk provides two means to setup, monitor and control the RAID array. First is a unique 2x20 character front-panel LCD display with password-protected push-button controls. Second is an RS-232 port that is easily connected to a standard terminal or PC with readily available terminal emulation software. You can operate the PC and thus the RAID array remotely with a modem. In all modes, you have complete control of the RAID array operation, you can monitor instantaneous status and watch for warnings, error conditions, rebuild operations, hot-spare status and more.

Host and O/S Independent
By using these two interfaces, FlashDisk avoids depending on graphical user interfaces (GUIs) which require the host and host bus, operating system and GUI software to be working properly. Since RAID monitors are frequently used when something is wrong, FlashDisk front panel and RS-232 terminal controls let you talk directly to the RAID array without relying on any other hardware or software to operate. Since there are only a few simple operations to control, the elegance of this approach will be appreciated most if you ever experience a hardware failure. While GUIs are, of course, pretty and easy to use, they unfortunately require special drivers for each operating system - and they quickly become out-of-date.

Front panel display
Network managers love the 2x20 character LCD front panel display. It provides instantaneous status information including host data transfer rate, initialize and rebuild progress reports and a full complement of RAID array status information.

With just a few front panel controls, you can examine the status of SCSI drives, review RAID mode setups, partition RAID arrays into multiple logical units, add or delete a spare drive, replace a failed drive and more. Using front panel controls including up/down menu scroll, ENT and ESC, you can move through the entire FlashDisk menu tree from the front panel.

The sequence to the left shows how to set up a spare drive on the first logical RAID array (LG=0). The status block shows that this is a RAID 5 array comprised of five drives with a total of 16 GB (16384 MB) of usable storage and there is currently no failed drive (FL=0) and no standby (hot-spare) drive (SB=0).

RS-232 Terminal

Naturally, with a larger display space, the terminal mode provides more on-screen information with less abbreviation and thus is recommended for ease in learning and for non-routine operations. The larger display format permits you to display and review complete drive tables, logical unit tables and partition tables without scrolling. The terminal mode lets you control the array at all levels from creation, deletion and partitioning of RAID arrays to enabling/disabling write back cache, enabling optional battery backup, entering and changing passwords and even resetting the controller. These capabilities put you or your designated service provider in full control of the FlashDisk RAID array at all times.

Normally, you just set up the RAID array once and forget it. However, when it comes time to upgrade, reconfigure, replace a failed drive or monitor rebuild status, you'll be happy to have the FlashDisk RAID array keep you completely informed about these matters. All this information is merely a few clicks away either on the terminal or LCD front-panel display.

Inquiry examples
You can set up the front panel to continuously monitor the performance of the RAID array. Many people feel a great deal of comfort watching this - knowing that when they see the “gas gauge” horizontal bar dancing across the display, they are reassured that everything is going alright. In fact, any deviation from normal behavior in this visual display may be an early warning to a problem and give rise to further inquiry.

Status Inquiry
The first thing to check in such a case is the Logical Drive Table. Just select “V” for View and edit logical drive to produce this display.

This display indicates that there is just one logical drive setup as a 16 GB RAID 5 array with five drives, one standby (hot-spare) drive and that no drives have failed.

A further inquiry using “P” for Partition logical drives produces the Logical Drive Partition Table which shows that the RAID 5 array is partitioned into three separate logical partitions which can be used by by the host operating system as separate logical volumes as if they were all physically different disk drives. With the dual hosting capability, these can even be used under different operating systems by different hosts. Two hosts can even share the data under operating systems that support clustering including Digital UNIX & OpenVMS, HP-UX, IBM AIX and SUN Solaris.

Rebuild
If a drive fails, the hot spare or new drive will be rebuilt. The RAID array will continue running transparently to users while reconstructing lost data from parity information. The rebuild process begins upon recognition of a fresh drive, whether just replaced or already in place as a standby. The rebuild occurs by recreating parity information or lost data in the background, sector by sector, while normal operations continue. The front panel display provides degree of completion information so you know what is happening and can anticipate when rebuild will be complete.

Upgrading the RAID array
Sooner or later you will need to upgrade the RAID array, either to add more storage, change to larger drives or just to replace a failed drive. Just select “A” to “view And edit scsi drives” from the main menu to review the SCSI drive table. The example below shows five Seagate 4 GB drives in the first five SCSI slots numbered 0 to 4 on two disk channels numbered 0 and 1. All the drives are in logical drive 0. You can select a new RAID level and reassign drives with the RAID level commands (be sure you have backed up your data - we recommend backing up twice, if possible) or assign one of the drives or a new drive as a standby (hot-spare) drive.

Summary
RAID arrays offer tremendous resiliency to a failed disk drive at reasonable cost in terms of number of extra drives required. To build and maintain RAID arrays, setup and monitoring is required. FlashDisk RAID provides convenient and accessible front panel displays and RS-232 ports to make it simple and easy.

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