Sabio Storage CM4 - Recoverability Options.

Configuration options for the CM-4’s drives range from maximum recoverability to maximum storage capacity.  The default setting is to provide you with a basic level of recoverability.

The two options for recoverability are Mirroring or Parity.

In the Mirroring mode, the total storage space is divided into two storage volumes of equal size, and every time something is saved, it is automatically saved to each volume.  You see just the combined output of both storage volumes so you don’t have to worry about saving files twice or making sure that each copy is on different drives.  In the Mirroring mode, even if one drive fails, the system can easily recover.  Under certain conditions, the system can even recover from two drive failures.  This method of recoverability uses the most amount of storage space???; the usable space is half of the total capacity of the CM-4.

In the Parity mode, the data is divided into two or three pieces and a parity bit, using an advanced formula. When written to the drive system, each data piece (along with the parity) is stored on a different drive.  If a drive fails, the system can rebuild the data on the missing drive by examining the data on the remaining drive. A minimum of three drives are needed in a system, and in this method, the total storage capacity is reduced by the capacity of one drive.

The three options for maximum storage capacity are Striping (also referred to as RAID 0), Linear, or just a bunch of disks (also referred to as JBOD).

When the system is configured for these maximum storage capacity options, it cannot recover lost data in the event of a drive failure.  This method is used only if maximum storage capacity is more important then recoverability.

In JBOD mode all drives show up as independent drives and function as such. If a drive should fail when the system is configured with the JBOD option,  you lose the data on the drive that fails, but everything else continues to function properly.  You can swap out the failed drive.

In Striping mode, all drives are combined  into one single storage space.  This method gives the fastest read performance, and is useful for applications where extremely fast data transfer is critical, such as in video or multi-track audio editing. Similar to the JBOD mode, Striping gives maximum capacity from the CM-4. However, because the striped data is split over multiple drives, if any single drive fails, ALL the data stored on the CM-4 is lost. Consequently, Striping mode should only be used on data which is backed up somewhere else or data that is not retained for long periods of time.

In Linear mode, all the drives are combined into a single storage space.  Disks are used one at a time until their capacity is reached. A single drive failure will cause you to lose all your data, the benefits of this method of storage configuration are limited

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