SoftNAS Cloud®’s FlexTier™ is a multi-tiered storage environment providing automated data movement based on managed policies, ensuring that your organization can create for itself the best solution possible for managing the data explosion their organizations are currently experiencing.

SoftNAS’ FlexTier provides the ability to seamlessly move blocks of data from high performance, low latency storage to more economical, larger capacity storage based on the value of the data. Data migration occurs automatically based on frequency of access. A given block of data that is not accessed regularly is relegated to the larger, economical storage provided. If a read request is submitted, no matter which tier the block of data resides, it will be satisfied and then that block will “reverse” migrate back up the tier hierarchy. 

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Preliminary Steps

To begin creating your FlexTier solution, several preliminary tasks should be completed:

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Note: If leveraging object storage (such as S3 or Azure Blob) for your infrequently accessed tiers, it is best practice not to use software RAID configuration for those tiers, as you will see limited performance gains, if any at all. If leveraging HDD block devices, RAID can be leveraged to improve performance.

Configuring FlexTier

1. As mentioned above, if FlexTier is to be leveraged, it is configured when creating the storage pool. To begin creating a FlexTier Configuration, select Storage Pools in the Storage Administration pane. 
   
   
   
   
   
2. Click Create, and then select the FlexTier  radio button. Click Next to begin the process.
   
   
   
   
3. First, we will be configuring the primary tier, also referred to as the Hot tier. This is the tier which will be most frequently accessed, and should provide a high performance index. 
   1. Assign a name to your Hot tier. 
   2. Select the RAID configuration that you planned for. In the below example software RAID is not leveraged (No RAID,JBOD). If leveraging RAID, additional disks would be selected, based on the RAID selection. 
   3. Select the desired Disks for your configuration. To be leveraged in Software RAID, disks must be of the same type and size. Ensure that the disks selected are those with the best performance index.
   4. Click Next. 
      
      
   
   
   
4. FlexTier requires a minimum of 2 tiers to be configured. The second tier is referred to as the "Warm" tier to differentiate it from later "Cold" tiers in more complex configurations. As you can see, the second tier operates the same as the primary.
   1. Provide the second tier a name.
   2. Determine the RAID level.
   3. Select disks of the storage type designated for your secondary tier (for example S3 or Blob object storage).
   4. If you plan to only have 2 tiers, select Next to proceed to the next step of the FlexTiers creation. To add additional tiers, select Add another tier.
      
      
   
   
   
5. For the purposes of documentation, we will stop at two tiers, as the process continues in the same manner. In other words, if mirroring this configuration, click 'Next' to proceed, rather than Add Another Tier. You will now assign a name to the FlexTier configuration. This will be the name used when creating the Volume to be used.  Select Finish to proceed.  If you need to make changes, you can select Back to return to the previous panel.
   
   
   
   
   
6. The final step in creating your FlexTier configuration is to establish the migration policy that will be used to govern each of the tiers. 
   
   1. Maximum Block Age refers to the amount of time a block of data has not been accessed, and is therefore eligible to be migrated to the next tier.
   2. Reverse Migration grace period refers to when blocks of data that have been accessed by a read inquiry will be moved back up the hierarchy.
      
      
   Note: Maximum Block Age does not apply to the last tier in the hierarchy. Nor does the Reverse Migration Grace Period apply to the Hot Tier.
   
   
   
   
   Both Maximum Block Age and Reverse Migration Grace Period are calculated to the second. The default time period for Maximum Block Age is 24 hours which, counted in seconds, equals 86400. The default for Reverse Migration Grace Period is by the same token 12 hours. To determine your settings, use these default values to calculate the time frame for each tier.

Managing an Existing FlexTier Migration Policy

Now that FlexTier has been configured, let's look at how to view and change settings for the Migration Policy on an existing FlexTier.

1. To open the Migration Policy, return to Disk Devices from the Storage Administration pane where you will see the disk listed as /dev/sdtiera, with the make and model of SoftNAS FlexTier Storage Device.
   
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2. When this disk is selected from the Disk Device list,  the Configure option will become available. Select Configure to open the Tiered Storage Configuration Wizard.
   
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3. In the Tiered Storage Configuration Wizard you can alter the migration policy as well as set specific parameters for the Hot tier.
   
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   1. The Migration interval in Device options controls the frequency that FlexTier will check for blocks needing to be migrated, based on the specific tier policies.
      
      
   2. Hot Tier Storage Threshold allows you to set a high-water mark on the tier which will force a migration to be done to move blocks to the secondary tier. In other words, if the data on the Hot Tier reaches the specified percentage, the blocks accessed the least frequently will be moved to ensure the Hot tier does not fill its available space.
      
      
   3. The Alternate Block Age is used when the “Hot Tier Threshold” has been met.  This will override the Maximum Block Age value specific to determine which blocks will be moved.
      
      
   4. You can also set a specific daily schedule for migrations to be allowed.  This is in a 24hour format.
      
      
4. Select Save once all the changes have been applied.

Increase Capacity of FlexTier 

Increasing the capacity of your FlexTier configuration is simple:

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