UnRAID 6/Storage Management

From unRAID
Revision as of 22:48, 11 February 2016 by Jonp (talk | contribs) (Created page with "= Assigning Storage Devices = right|500px Now that you’ve booted up your unRAID Server, you are ready to begin setting up your first array....")
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Assigning Storage Devices

Configuringarray1.png

Now that you’ve booted up your unRAID Server, you are ready to begin setting up your first array. The boot process shouldn’t take more than a few minutes and when completed, open a web browser from your Mac or PC and navigate to http://tower (or http://tower.local if using a Mac). The first page you will be brought to is the unRAID Main tab, where you will select the devices to assign to slots for parity, data, and cache disks. Assigning devices to unRAID is easy! Just remember these guidelines:

  • Always pick the largest storage device available to act as your parity device. When expanding your array in the future (adding more devices to data disk slots), you cannot assign a data disk that is larger than your parity device. For this reason, it is highly recommended to purchase the largest HDD available for use as your initial parity device, so future expansions aren’t limited to small device sizes.
  • Do not assign an SSD as a data/parity device. While unRAID won’t stop you from doing this, SSDs are only supported for use as cache devices due TRIM/discard and how it impacts parity protection. Using SSDs as data/parity devices is unsupported and may result in data loss at this time.
  • Using a cache will improve array performance. It does this by redirecting write operations to a dedicated disk (or pool of disks in unRAID 6) and moves that data to the array on a schedule that you define (by default, once per day at 3:40AM). Data written to the cache is still presented through your user shares, making use of this function completely transparent.
  • Creating a cache-pool adds protection for cached data. If you only assign one cache device to the system, data residing their before being moved to the array on a schedule is not protected from data loss. To ensure data remains protected at all times (both on data and cache disks), you must assign more than one device to the cache function, creating what is called a cache-pool. Cache pools can be expanded on demand, similar to the array.
  • SSD-based cache devices are ideal for applications and virtual machines. Apps and VMs benefit from SSDs as they can leverage their raw IO potential to perform faster when interacting with them. Use SSDs in a cache pool for the ultimate combination of functionality, performance, and protection.

NOTE: Your array will not start if you assign more devices than your license key allows.

Starting and stopping the Array

Normally following system boot up the array (complete set of disks) is automatically started (brought on-line and exported as a set of shares). But if there's been a change in disk configuration, such as a new disk added, the array is left stopped so that you can confirm the configuration is correct. This means that any time you have made a disk configuration change you must log into the Management Utility and manually start the array.

Disk configuration changes

Here are the normal configuration changes you can make:

  • You add one or more new disks.
  • You replace a single disk with a bigger one.
  • You replace a failed disk.
  • You remove one or more data disks

Add one or more new disks

This is the normal case of expanding the capacity of the system by adding one or more new hard drives:

  1. Stop the array.
  2. Power down the server.
  3. Install your new hard drive(s).
  4. Power up the unit.
  5. Assign the new storage device to a disk slot using the unRAID webGui.
  6. Start the array.

When you Start the array, the system will mount the disk and automatically begin to clear the disk which is required before it can be added to the array. The clearing phase is necessary to preserve the fault tolerance characteristic of the array. If at any time while the new disk(s) is being cleared, one of the other disks fails, you will still be able to recover the data of the failed disk. Unfortunately, the clearing phase can take several hours depending on the size of the new disks(s). Once the disk has been cleared, an option to format the disk will appear in the webGui. Once the format is complete, the disk is added to the array automatically.

The capacity of any new disk(s) added must be the same size or smaller than your parity disk. If you wish to add a new disk which is larger than your parity disk, then you must instead first replace your parity disk. (You could use your new disk to replace parity, and then use your old parity disk as a new data disk.)

Replace a single disk with a bigger one

This is the case where you are replacing a single small disk with a bigger one:

  1. Stop the array.
  2. Power down the unit.
  3. Replace smaller disk with new bigger disk.
  4. Power up the unit.
  5. Assign the new bigger disk using the unRAID webGui.
  6. Start the array.

When you start the array, the system will reconstruct the contents of the original smaller disk onto the new disk. Upon completion, the disk's file system will be expanded to reflect the new size. You can only expand one disk at a time.

If you are replacing your existing Parity disk with a bigger one, then when you Start the array, the system will simply start a parity sync onto the new Parity disk.

A special case exists when the new bigger disk is also bigger than the existing parity disk. In this case you must use your new disk to first replace parity, and then replace your small disk with your old parity disk:

  1. Stop the array.
  2. Power down the unit.
  3. Replace smaller parity disk with new bigger disk.
  4. Power up the unit.
  5. Assign the new bigger disk using the unRAID webGui.
  6. Start the array.
  7. Wait for Parity-Sync to complete.
  8. Stop the array.
  9. Power down the unit.
  10. Replace smaller data disk with your old parity disk.
  11. Power up the unit.
  12. Assign the old parity disk using the unRAID webGui.
  13. Start the array.

Replace a failed disk

This is the case where you have replaced a failed disk with a new disk:

  1. Stop the array.
  2. Power down the unit.
  3. Replace the failed hard disk with a new one.
  4. Power up the unit.
  5. Assign the replacement disk using the unRAID webGui.
  6. Start the array.

When you Start the array after replacing a failed disk, the system will reconstruct the contents of the failed disk onto the new disk; and, if the new disk is bigger, expand the file system.

You must replace a failed disk with a disk which is as big or bigger than the original and not bigger than the parity disk. If the replacement disk is larger than your parity disk, then the system permits a special configuration change called swap-disable.

For swap-disable, you use your existing parity disk to replace the failed disk, and you install your new big disk as the parity disk:

  1. Stop the array.
  2. Power down the unit.
  3. Replace the parity hard disk with a new bigger one.
  4. Replace the failed hard disk with you old parity disk.
  5. Power up the unit.
  6. Assign the bigger disk to your parity slot and the old parity disk to your failed disk slot using the unRAID webGui.
  7. Start the array.

When you start the array, the system will first copy the parity information to the new parity disk, and then reconstruct the contents of the failed disk.

Remove one or more data disks

In this case the missing disk(s) will be identified. If there is only one missing disk when you start the array it will be marked as failed. All data disks will be exported (including the missing one), but the system will be running unprotected; that is, if a disk fails you will lose data.

If there are two or more missing disks, you can not start the array. In this case you must either put the disks back, or perform a New Config operation from the Tools -> New Config page in the unRAID webGui.

Reset array configuration

When the array is Stopped, you can reset all your disk assignments back to their default state (unassigned). This is useful if you need to remove a disk from an existing array that you do not intend to replace or return or if you simply wish to start fresh with a new configuration from scratch. To do this, visit the Tools -> New Config page in the unRAID webGui. Click the checkbox and click apply to perform the operation.

Check parity

When the array is Started and parity is already valid, there is a button under Array Operations labeled Check which will initiate a background Parity-Check function. Parity-Check will march through all data disks in parallel, computing parity and checking it against stored parity on the parity disk. If a mismatch occurs and the "Write corrections" checkbox is left enabled, the parity disk will be updated (written) with the computed data and the Sync Errors counter will be incremented. If the checkbox is NOT checked for "Write corrections" parity errors will be notated but not actually fixed during the check operation.

The most common cause of Sync Errors is power-loss which prevents buffered write data being written to disk. Anytime the array is Started, if the system detects that a previous unsafe shutdown occurred, then it automatically initiates a Parity-Check.