Stellar Converter for OST Software Benchmark Report

Sponsored by Stellar Data Recovery

About the software

Stellar Converter for OST is a flagship file conversion software from Stellar®. It specializes in converting inaccessible OST files into PST format so as to reinstate mailbox data access by way of opening the resultant PST file in Outlook.

The software retrieves data from a mailbox that may have been “locked inside” an OST file due to reasons such as deletion or removal of user account from mail server, server crash or database dismount, and disrupted network connectivity. Stellar Converter for OST offers to deliver high Performance and Reliability as key demonstrable benefits associated with its core “file conversion” utility.


Takes the least amount of time for converting OST file to PST.
Guarantees 100% data integrity after OST to PST conversion process.
Converts and extracts all ‘user-specified’ mailbox components in PST.
Delivers consistent OST to PST conversion experience, without any glitch.

Software benchmark study: Overview

Stellar conducted this software benchmark study in collaboration with Lisa Hendrickson – an industry expert and solutions consultant for Microsoft Outlook, Exchange, and Office 365. Lisa has independently verified the authenticity & integrity of the methodology described in this report to measure and quantify the performance of the tested OST to PST conversion tools. Based on rigorous testing & reproduction of the outcomes of this lab study, Lisa attests to and endorses the findings of this benchmark study.

Stellar conducted this software benchmark study to rigorously test the Performance and Reliability aspects of Stellar Converter for OST in the context of the aforementioned key benefits (value propositions).

This lab study of the software intends to establish “objective” and “quantifiable” benchmarks for these four key benefits in terms of the metrics of — Speed, Precision, Completeness, and Consistency.

Benchmark study: Purpose

The purpose of this study is to educate the intended users of OST to PST converter software by way of presenting an authentic and unbiased report that is traceable, meaning, the results and findings of the study can be principally reproduced and verified in the test environment. The study also intends to serve as an empirical source that can be trusted upon for making informed decisions with regard to considering OST to PST conversion software tools.

Benchmark study: Approach

The study is based on taking a competitive evaluation approach, comparing Stellar Converter for OST with other similar software to benchmark performance and reliability parameters.

The competing software considered in this study include — OST2, Kernel for OST to PST, and SysTools OST Recovery.

The study evaluated all 4 software consistently within the framework of standard software testing practices, system setup, and process rigor.

Test samples

The test sample comprised of a batch of four inaccessible OST files — sized 1.95GB, 7.05GB, 14.4GB, and 27.6GB — each to be converted by using OST2, Kernel for OST to PST, SysTools OST Recovery, and Stellar Converter for OST. Each of these four OST files comprising the test sample was associated with Outlook 2016.

Test environment and study approach

The benchmark testing was conducted at the software R&D facility of Stellar. A dedicated environment was set up for the benchmark tests, with standard hardware and software configuration to ensure uniform provision of compute resources for the four competing software.

The test machine was an Intel Core i5 computer with 6GB RAM and Windows 8 operating system. Further, Microsoft Office 2016 was installed on the machine.


  • All four software were first installed on the test machine. Next, each software was run sequentially on an individual OST file (1.95GB) to convert it into PST.
  • OST to PST conversion durations and final PST file sizes were recorded respectively for each software.
  • After completing one full cycle of ‘conversion’ and ‘performance recording’ for the first sample, the process was then repeated for the remaining 3 OST test samples.

Study findings and takeaways


  1. CONVERSION TIME (Time per Sample, Conversion Rate per GB, & Reliability)


    1. Stellar Converter for OST took the least time to convert 3 out of 4 OST files, with a minimum four min. for 1.75GB OST a maximum 127 min. for 14.4GB OST.
    2. Kernel for OST to PST took the highest time for OST to PST conversion for all OST samples, with maximum 45 hours to convert the 14.4GB OST.

    CONVERSION RATE (Refer Fig. 2)

    1. Stellar Converter for OST performed overall fastest per GB conversion of OST to PST, taking an average 7.08 min.
    2. Kernel for OST to PST did slowest per GB conversion, taking an average 89.96 min. to convert per GB of OST to PST.
    3. OST2 performed 2nd fastest per GB conversion of OST to PST. However, it crashed while attempting to convert the largest 27.6GB OST file.


    1. The resultant PSTs after converting 1.75GB, 7.05GB, and 27.6GB OST files were larger than the source file in the case of all 4 software. This indicates that all the competing software were able to extract complete data from these 3 OST files.
    2. Conversion of the 14.4-GB OST file with OST2 resulted in a 13.9GB PST file, roughly 0.5GB smaller than the source OST. This indicates that OST 2 couldn’t extract some mailbox items from the 14.4GB-OST file.

    PRECISION (Refer Fig. 4 & Fig. 5)

    1. SysTools OST Recovery and Stellar Converter for OST extracted approx. the same number of total 246K+ mailbox items and 4.9K mailbox items/GB of OST, aggregated for all 4 sample OST files. However, the aggregate size of the resultant PST file in case of SysTools is 5GB larger than that for Stellar Converter for OST. This likely indicates that SysTools OST Recovery had also extracted some irrelevant data such as blank emails, junk emails, etc. thereby inflating the output PST file size.
    2. Kernel for OST to PST didn’t provide any details of the number of mailbox items extracted from the OST files. Therefore, precision of the software couldn’t be ascertained.

Benchmark ratings

The study establishes objective benchmarks for OST file conversion software by quantifying the Performance and Reliability in terms of Speed, Precision, Completeness, and Consistency. Following are the performance benchmark ratings for the 4 software on a scale of [0–5], as established by this study.

* OST2 Completeness rating = 3.33

Completeness rate = 2/3 [=0.66] (completed OST to PST in 2 out of 3 conversions)

2/3 = X/5 {calculation for benchmark rating out of the highest rating of 5} X = 3.33

ϯ OST2 Consistency rating = 3.75

Consistency rate = 3/4 [0.75](converted OST to PST in three out of four test attempts, crashed while attempting to convert the 27.6GB OST file)

3/4 = X/5 {calculation for benchmark rating out of the highest rating of 5} X = 3.5

# Kernel for OST to PST ‘Precision’ rating = 2.5

Average rating is assigned for Precision, as the software doesn’t display mailbox preview to assess the “Precision” parameter.


This study used a standard approach to test and benchmark OST to PST converter software performance on the parameters of Speed, Precision, Completeness, and Consistency.

  1. Speed: Based on the findings, Stellar Converter for OST took the least amount of time to convert the OST file to PST file for all 4 test samples. This establishes Stellar Converter for OST as the fastest OST to PST conversion tool.
  1. Precision: Mapping the extracted mailbox item count to the resultant PST file size, the study reports that SysTools OST Recovery gets significantly larger PST files in the case of 7.05GB and 14.4GB OST files. This deviation in size is attributed to extraction of junk mailbox items based on actual verification of the mailbox data. Next, OST2 extracted only 39K items as compared to 83K mailbox items extracted with Stellar Converter for OST. Further, Kernel for OST to PST didn’t provide any details on the number of mailbox items extracted. Based on these findings, Stellar Converter for OST attained the highest benchmark rating on “conversion precision” metric.
  1. Completeness: Both SysTools OST Recovery and Stellar Converter for OST software extracted the most (and almost similar) number of mailbox items for all OST test samples. Therefore, these tools have attained the highest benchmark ratings on the “conversion completeness” metric.
  1. Consistency: OTS2 crashed while converting the largest OST file sample of 27.6GB size. The rest of the three software tools were able to convert all the OST files without crash or sluggishness.

Download the Stellar Converter for OST Software Benchmark Report in PDF format
(no registration required)

Featured image: Shutterstock

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Scroll to Top