---
title: "VAST Probe Quickstart"
slug: "vast-probe-quickstart"
description: "Quick start guide for VAST Probe setup, prerequisites, hardware sizing, and download steps, ensuring optimal performance."
updated: 2026-10-30T19:22:42Z
published: 2026-10-30T19:22:42Z
canonical: "docs.vastdata.com/vast-probe-quickstart"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# VAST Probe Quickstart

## Prerequisites

- Linux OS ([Ubuntu 20](https://releases.ubuntu.com/focal/)/[CentOS 8](https://www.centos.org/centos-stream/) Recommended)
  - Ubuntu 18 & CentOS 7 Minimum Required
- python3
- Docker
- screen
- wget

## Sizing The Probe Hardware or Virtual Machine

Review [VAST Probe Requirements](/kb/docs/vast-probe-requirements)

- **RAM** is reserved for the **operating system** and the **probe runtime image.**
  - 20% is set aside automatically by the **probe launcher.**
- **RAM** is also used for the **file name cache.**
  - This is 50 bytes per file scanned.
- **RAM** or **SSD-backed local disk** is used for a **hash database.**
  - The **hash database** is where the pros scanned blocks.
  - The **hash database** should be **at least 0.6% of the data size.**
  - If there is sufficient **RAM**, the probe will use **RAM** for the **hash database.**
  - If there is insufficient **RAM**, the probe will use **an SSD-backed local disk** for the **hash database.**
- Any remaining unallocated **RAM** will be used for a **read cache.**

## Download Probe Bundle

To download the probe, refer to the instructions in [Downloading the VAST Probe](/kb/docs/downloading-the-vast-probe).

If you do not have access to the instructions, please contact your VAST representative. They can provide download instructions.

## Expand & Verify Download

Now that you've downloaded the probe, you'll need to untar it and verify the download.

```plaintext
export PROBE_BUILD=935553
tar -xzf ${PROBE_BUILD}.probe.bundle.tar.gz
ls -l
```

Note: image may not show current build numbers.

![The provided terminal screenshot shows that the user has exported `PROBE_BUILD=513711`, extracted a `.tar.gz` file using this build number, and listed its contents to confirm the extraction was successful, including files such as `probe.bundle.tar.gz`, `probe.image.gz`, and `probe_launcher.py`.](https://cdn.us.document360.io/89b91113-5dc6-49db-86ec-57b16dc8ce56/Images/Documentation/0019733c-1575-4578-a99b-126f29e10d7a.png?sv=2026-02-06&spr=https&st=2026-11-08T09%3A29%3A07Z&se=2026-11-08T10%3A29%3A07Z&sr=c&sp=r&sig=zOicL8Ck3%2FkZ%2B8BHlPFNBrsSvPdfAF7EqMkzs0PBh88%3D)

## Mount Filesystems Selected to Be Probed

Validated Filesystems Include, But Are Not Limited To:

- NFS
- Lustre
- GPFS
- S3 with [goofys](https://github.com/kahing/goofys)
- CIFS/SMB

For the most accurate results, do not use *root-squash*

It's recommended to set *read-only* access on the mounted filesystem

## Create Probe Directories

Change */mnt/* to the **SSD-backed local disk** to be used by the probe for the **hash database** and **logging** directories

```plaintext
sudo mkdir -p /mnt/probe/db
sudo mkdir -p /mnt/probe/out
sudo chmod -Rf 777 /mnt/probe
```

## Size of the Data Set

- The input to the probe is a defined directory (*--input-dir*)
- The probe will automatically query the input filesystem about space consumed and file count ([inodes](https://en.wikipedia.org/wiki/Inode)), and use that in its calculations
- Depending on the method of mounting and underlying storage, this can often provide an inaccurate query response
- It's highly recommended that manual estimated entries be defined for space consumed (*--data-size-gb*) and file count (*--number-of-files*)
- These estimates do not have to be accurate; round up reasonably

## Running The Probe

The probe runs as a foreground application. This means that if your session is closed for whatever reason, the probe will stop. It's recommended to run the probe as a [screen](https://linux.die.net/man/1/screen) session.

Here is an example of a command line. Edit the **bold variables** for the environment:

***NOTE:*** Use **underscores** instead of **spaces** in **COMPANY_NAME** and **WORKLOAD**

```plaintext
export DB_DIR=/mnt/probe/db
export OUTPUT_DIR=/mnt/probe/out
export INPUT_DIR=/mnt/filesystem_to_be_probed/sub_directory
export INPUT_SIZE_GB=10000
export QTY_FILES=1000000
export COMPANY_NAME=Your_Amazing_Company
export WORKLOAD=Describe_Your_Workload
```

Start the probe: (This may take up to five minutes to start displaying output)

```plaintext
sudo python3 ./probe_launcher.py \
--probe-image-path ${PROBE_BUILD}.probe.image.gz \
--input-dir $INPUT_DIR \
--metadata-dir $DB_DIR \
--output-dir $OUTPUT_DIR \
--data-size-gb $INPUT_SIZE_GB \
--number-of-files $QTY_FILES \
--customer-name ${COMPANY_NAME}---${WORKLOAD}
```

### 

### Example One: Small Data Sets

To probe the directory *interesting_data* of **15 TB in-use** and **5,000,000 files** at the **company ACME**, the command would be:

```plaintext
sudo python3 ./probe_launcher.py \
--probe-image-path ${PROBE_BUILD}.probe.image.gz \
--input-dir /mnt/acme_filer/interesting_data \
--metadata-dir /mnt/data/probe/db \
--output-dir /mnt/data/probe/out \
--data-size-gb 15000 \
--number-of-files 5000000 \
--customer-name ACME---Interesting_Data
```

### Example Two: Larger Data Sets

To probe the directory *fascinating_data* of **60 TB** **in-use** and **750,000,000 files** at the **company FOO**, and are using defined parameters for **RAM** and **SSD-backed local disk,** the command would be:

```plaintext
sudo python3 ./probe_launcher.py \
--probe-image-path ${PROBE_BUILD}.probe.image.gz \
--input-dir /mnt/foo_filer/fascinating_data \
--metadata-dir /mnt/data/probe/db \
--output-dir /mnt/data/probe/out \
--data-size-gb 60000 \
--number-of-files 750000000 \
--customer-name FOO---Facinating_Data
```

### Example Three: Performance Throttling

To probe the directory *riviting_data* of **250 TB** **in-use** and **1,250,000,000 files** at the **company Initech**, using defined parameters for **RAM** and **SSD-backed local disk,** but wishing to have a **lower performance impact** on the filesystem, the command would be:

```plaintext
sudo python3 ./probe_launcher.py \
--probe-image-path ${PROBE_BUILD}.probe.image.gz \
--input-dir /mnt/initech_filer/riviting_data \
--metadata-dir /mnt/data/probe/db \
--output-dir /mnt/data/probe/out \
--data-size-gb 250000 \
--number-of-files 1250000000 \
--number-of-threads 4
--customer-name Initech---Riviting_Data
```

**Note** the *--number-of-threads* flag. By default, the probe uses all CPU cores in the system, but this can be used to throttle performance and reduce the potential impact on the scanned filesystem.

## Other Probe Flags

While the probe is running and after completion, telemetry logs are automatically uploaded to VAST. To prevent this, add the following flag:

```plaintext
--dont-send-logs \
```

If you wish to send file names with the default telemetry logs, add the following flag:

```plaintext
--send-logs-with-file-names \
```

Probing filesystems that contain snapshots can often cause recursion issues and inaccurate results. As a result, the probe automatically ignores directories named .snapshot. If your file system uses another convention, use the --regexp-filter command. If, for some reason, you want the probe to read the .snapshot directories, specify false rather than true for --filter-snapshots.

```plaintext
--filter-snapshots \    (this is the default)
```

Adaptive chunking was introduced with VAST 4.3 and this latest ( ) probe version. Under most circumstances, the probe should be run with adaptive chunking. However, you can disable that feature by specifying this flag:

```plaintext
--disable-adaptive-chunking \
```

## Understanding the Results

Once started, the probe will display the current projected data reduction. Once completed, the probe will display output, which is further described in [Understanding VAST Probe Output](/kb/docs/understanding-vast-probe-output)

## Re-Running The Probe

The **hash database** must be empty before running the probe again:

```plaintext
sudo rm -r /mnt/probe/db/*
```

## Troubleshooting

Refer to the [VAST Probe Troubleshooting](/kb/docs/vast-probe-troubleshooting) and contact your VAST System Engineer for assistance.