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Use the links below to review key features and terminology related to LaCie RAID Manager.
| Configuration |
|---|
| Array RAID RAID level Initialization Spare drive Stripe size |
| Maintenance |
| Auto rebuild Consistency check Disk check Poll SMART Status |
| Performance |
| Cache |
An array is a combination of two or more physical disks that are presented to the operating system as a single volume.
RAID stands for redundant array of independent disks. RAID contains the word array, and the two terms are often used interchangably.
Disks are combined into different RAID configurations known as RAID levels. The RAID level you choose depends on which storage attributes are most important to you:
| Capacity | The total amount of data you can store |
| Performance | The speed at which data is copied |
| Protection | The number of disks that can fail before data is lost |
Initializing an array can help prevent errors while handling data. The following options are available when creating a custom array:
| None | The data check is skipped. This option is not recommended as you can encounter data errors and you cannot perform a consistency check on the array. |
| Fast | Fast initialization is a destructive process that erases all data on the array, including the Master Boot Records (MBR) on all physical disks. Use fast initialization if you wish to perform a cursory check before starting a project. However, this option does not perform a thorough check of the array. Therefore, a Fast initialization does not help to prevent data handling errors. Since it is not a full initialization, consistency checks are not available when using Fast on the array. |
| Background | A full initialization that guarantees all mirror or parity blocks are checked and updated to ensure consistency of data on the array. A background initialization deletes data previously stored on the array. However, since the process runs in the background, you can use the array during the initialization. Any data written on the array during during the background initialization is safe. A background initialization can take multiple hours based upon the total capacity of the array. Performance is impacted during the initialization process, especially when working on high-end video or graphic projects. |
| Foreground | A full initialization that guarantees all mirror or parity blocks are checked and updated to ensure consistency of data on the array. A foreground initialization is faster than background initialization, but you can’t write new data to the array while the initialization is underway. |
A hard drive designated as a spare is only used if a hard drive in an array fails.
A spare hard drive waits to be used in the event a single hard drive in an array fails. If auto rebuild is enabled, a spare hard drive automatically takes the place of a failed hard drive. As part of a rebuild, the device synchronizes data to the spare hard drive so that it can be assimilated into the array. A hard drive must be assigned as a spare in order for auto rebuild to synchronize data.
The greatest advantage of having a spare hard drive is the reduction of time wasted waiting to rebuild an array. That is, if all hard drives in the enclosure are being used for one or more arrays, there are no hard drives available to assign as a spare to take over for a failed disk. In such a case, you must contact LaCie support to replace a hard drive purchased through LaCie, or find a replacement if the hard drive did not ship with the device. Since a failed hard drive generally means the array is degraded, the RAID can no longer protect your data. Further, if another hard drive in the array fails, the data is lost. Therefore, a good amount of time and, potentially, data can be lost if a replacement hard drive is not available.
The clear disadvantage to having a spare is losing storage space since a spare hard drive sits on the side waiting for a hard drive to fail. While acting as a spare, the hard drive’s storage space cannot be used.
LaCie RAID Manager has two spare drive options:
| Global spare drive | Global spare drives can be used by any array. This option is good if you have more than one array. |
| Dedicated spare drive | Dedicated spare drives are used exclusively for rebuilding a specific array. |
A stripe represents a single data block on the array. Stripe size is the amount of data (in KB) written to one disk before moving to the next disk in the array. The range of stripe sizes includes 64K, 128K, 256K, 512K and 1024K. The choice of stripe size varies by device.
The larger the stripe size, the longer it takes for the RAID controller to read from and write to data blocks on the physical disks. Consider the following when configuring the stripe size:
A stripe size can be assigned while configuring the array.
| Go to |
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| Create an array |
When auto rebuild is enabled, the device automatically rebuilds a degraded array once a spare hard drive is available. A degraded array generally means that one or more hard drives are missing or experiencing errors.
The amount of disks an array can lose depends upon the RAID level. A RAID 5 array can lose one hard drive, while a RAID 6 array can lose two hard drives. The rebuild cannot begin if there are no dedicated or global spare hard drives.
If auto rebuild is disabled, you can rebuild a degraded array by exchanging a defective hard drive with a healthy hard drive and manually initiating a rebuild.
A consistency check tests the integrity of parity or mirrored data on the array. Consistency checks are highly recommended as part of regular maintenance for arrays. Consider running a consistency check when an array is not performing as expected.
You can run a consistency check on an array that has had a background or foreground initialization. The consistency check option is not available for arrays with a fast initialization or no initialization. Additionally, a consistency check is not available when a background initialization or a disk check is in progress.
While a consistency check scans the integrity of parity or mirrored data on the array, disk check searches for errors on a single hard drive. Run disk check on an individual disk as part of regular maintenance.
A disk check is not available when an initialization or consistency check is in progress.
| Go to |
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| Check a disk in an array |
SMART (Self-Monitoring, Analysis and Reporting Technology) is a hardware monitoring system that reports various indicators of drive reliability. You can configure LaCie RAID Manager to gather and report the SMART status for each disk in the enclosure.
Caching media can improve your LaCie device’s performance by keeping files in a select location rather than sending them directly to the array’s storage. Transfer speeds are faster since your computer retrieves data directly from the cache rather than searching the hard drives. Caching data optimizes your LaCie product for better performance.
There are two options for caching media:
| Array cache | Cache media on the array. Data is stored on a buffer before being flushed to the array at the appropriate time. |
| Disk cache | Cache media on disks. Data is stored temporarily on the disks’ caches before it is moved to the array. |
While caching data is recommended to improve performance, there is a potential drawback in regard to protecting data and data corruption. In the event of power failure, data integrity can be lost if the data has not been fully transferred from the cache to the array. Make certain to use a stable power supply that cannot be interrupted, such as an uninterruptable power supply (UPS). A UPS allows you to safely shut down the LaCie device if the electricity suddenly terminates at your facility or office.
When data caching is disabled, all data is accessed from the array. This option is recommended when data protection is critical to your workflow. While access to data is not as fast when disk caching is disabled, transfer rates remain quite high due to the use of a hardware RAID controller and your version of Thunderbolt technology.
| Go to |
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| Change cache settings |