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How InfoScale SmartTier Distributes Data Across Tiers to Optimize Storage Costs

Level 1

In the storage world, enterprises struggle with the high cost and complexity of managing and storing massive amounts of data. It is common to have deployments storing all data the same way regardless of the I/O activity. Determining what data can be stored in lower-cost storage and dynamically moving this data is nearly impossible without functionality that performs this automatically. While many storage solutions include some tiering capability, they lack a heterogeneous enterprise-level view resulting in IT having to manage multiple different tiering solutions individually. This is where the Veritas SmartTier feature of InfoScale helps.  

Unlike point solutions, InfoScale enables IT organizations to manage their storage infrastructures in a centralized fashion. Amongst the many advanced storage features, InfoScale includes dynamic storage tiering capabilities that can automatically move older data to less expensive storage devices, transparently and without downtime. You can create policies that will dynamically move files based on date created, last time accessed, size, or name.Smart Tiering Figure 1.pngSmartTier feature in VxFS functions on top of multi-volume file systems, i.e. file systems occupied on two or more virtual volumes. It allows administrating the file placement on the different virtual volumes as per the file placement policy. If the file fits the placement policy criteria, InfoScale will relocate it to the respective logical volumes.

Use Case

Enterprises typically contain a mix of files that employees access frequently and others that are not. To gain the best performance without the expense of moving the entire volume to costlier SSD storage, SmartTier places the frequently accessed files on the faster SSD storage and leaves the less busy files on HDD.

Using SmartTier 

With SmartTier, an administrator can create multi-volume file systems that contain virtual volumes with a mix of SSDs and HDDs.

You can create a placement policy based on the I/O activity patterns that will transparently move data between tiers depending on the file's I/O activity. A placement policy includes the following two attributes, both of which SmartTier uses to determine what data to tier files off SSD:

Average IO activity criteria

  • The average criteria allow you to specify the I/O temperature value as a ratio of per-file activity that occurs over the time specified by the <PERIOD> element compared to the overall file system activity that occurs over a more extended period of time.

Prefer attribute

  • In the case of a solid-state disk(SSD)-based tier, you might want to relocate a file to an SSD as soon as there is a marked increase in the I/O activity. 
  • However, once Veritas File System (VxFS) has relocated the file to an SSD, it may be beneficial to keep the file on the SSD as long as the activity remains high to avoid frequent thrashing.
  • The Prefer attribute can take two values: low or high. If you specify low, Veritas File System (VxFS) relocates the files with the lower I/O temperature before relocating the files with the higher I/O temperature. If you specify high, VxFS relocates the files with the higher I/O temperature before relocating the files with the lower I/O temperature.

File placement policy

When creating a file placement policy, it is important to understand I/O temperate, which is the measure of I/O activities during the specified PERIOD. It is calculated by read and write activities happening on the file system.

I/O temperature = (total number bytes read/write as per FCL) / ((total size of all Files in FCL) * Period)

FCL is File Change Log that records file system changes such as creates, links, unlinks, renaming, data appended, data overwritten, data truncated, extended attribute modifications, holes punched, and miscellaneous file property updates.

It can be calculated based on reads, writes, or both reads and writes. For calculating the Average Temperature of a file system, only active files (which have entries in the FCL) during "AveragePeriod" are considered.


  • As per the placement file policy and I/O activity criterion, InfoScale will move data to different tiers upon running the policy enforcement operation.


Keeping a few files on the most appropriate storage tier based on the I/O activity is easy. An administrator can monitor I/O activity, move files, and adjust application procedures as necessary to optimize storage and I/O resources. The complication arises in data centers with millions of files that fluctuate between high and low I/O activity and greater and lesser criticality. Humans can't track I/O activity on this scale. With SmartTier implementation, you can achieve this complex task easily and intelligently. You can use Cloud as a tier as well and plan their data storage life cycle. To understand more about the Cloud tiering, you can refer to the Clustered file system tiering to the cloud blog.