LSFS Container Technical Description

Published: August 2015

This document is intended for experienced Windows system administrators and IT professionals who would like to know more about StarWind Virtual SAN solution and better understand how StarWind Virtual SAN works. It provides the description of the LSFS container and explains its features i.e. deduplication, defragmentation etc., which should give the end user the necessary knowledge for its implementation into the system.

StarWind Virtual SAN® is a native Windows software-defined VM storage solution. It creates a VM-centric and high performing storage pool purpose-built for virtualization workloads. StarWind Virtual SAN delivers supreme performance compared to any dedicated SAN solution since it runs locally on the hypervisor. StarWind Virtual SAN includes the Log-Structuring File System technology, which coalesces small random writes, typical for virtualized environment, into the stream of big sequential writes. As a result, the performance is increased and the flash life is prolonged.

The Features of LSFS and Their Description

What is LSFS: Log-Structured File System is a journaling file system that keeps track of the changes that will be made in a journal. This file system keeps no data, only the changes. It supports built-in automatic and manual defragmentation, deduplication on the fly and snapshots.
How Snapshots work: Every snapshot is incremental and occupies additional space; snapshots are created every 5 minutes by default and then deleted; a snapshot can be taken manually as well.
How Defragmentation works: Defragmentation works continuously in the background. Each file-segment will be defragmented when data capacity exceeds of allowed value.
How Deduplication works: Unique chunks of data are identified and stored while being analyzed.
Performance boost: The log structuring uses Redirect-on-Write for snapshotting, writes, etc. No matter which access pattern is used, the underlying storage always receives 4 MB blocks. LSFS coalesces multiple smaller random writes into a single sequential big write I/O, which allows achieving up to 90% raw sequential write performance
Overprovisioning: Overprovisioning of LSFS devices is 200%
LSFS based HA synchronization: HA based on LSFS uses snapshots for sync purposes, and it syncs only latest changes after any failure.

Current LSFS Limits and Requirements

1. Required RAM (it is not related to L1 cache):
4.6 GB of RAM per 1 TB initial LSFS size (deduplication is disabled)
7.6 GB of RAM per 1 TB initial LSFS size (deduplication is enabled)
2. LSFS maximum size is 11 TB
3. Overprovisioning is 200%
4. The physical block size of LSFS device is 4k

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