IMPORTANT NOTE: Starting from 14869 build, the LSFS device feature was excluded and deprecated. Please remove all Asynchronous replicas and LSFS devices before the update. See more information in the release notes:


  1. When should I use lsfs and why not stick to thick provisioning?
    • LSFS module was developed specifically to get maximum performance out of cheap SATA spindles combined with L1/L2 caching.
  2. Why do I have many .spsx files in my StarWind storage pool?
    • These are snapshots created by LSFS, please never delete them since they serve a good purpose – ability to restore the device from the last stable checkpoint.
  3. How does defragmentation work in StarWind LSFS module?
    • Since defragmentation is an automatic process, it scans data sectors in a particular point in time, if these sectors have at least 40 % or more free space, data from them are transferred to another sector, thus thin-provisioned disk is fattening a bit. This sector is 100 % filled and all other ones get deleted. The scheme is as follows (just an example): Initially – 10 sectors, 7 of them 70 % free, 3 of them 89 % full; data from 7 sectors go to 2 sectors, fill them to the top (100% each), so now we have 12 sectors in total; we remove 7 sectors; as a result we have 5 sectors only. All this is happening in real time.
  4. How much extra space should I overprovision for LSFS device?
    • LSFS device will consume 2.5 to 3 times more space than specified in StarWind management console.
  5. When I specify the size of LSFS device, does it mean I can only put the data of this size?
    • No, after deduplication and defragmentation you will shrink actual space, so you can put a bigger amount of data on the device.
  6. How do I disable defragmentation?
    • It is enabled by default and cannot be disabled.
  7. How do I disable/enable deduplication?
    • Currently it is not possible to do so on the fly, but you can disable/enable deduplication during creation of LSFS device: when choosing “thin-provisioned” option, click on “Options” and check or uncheck “deduplication” feature.
  8. How much RAM do I need for LSFS device to function properly?
    • 4.6 MB of RAM per 1 GB of LSFS device with disabled deduplication,
    • 7.6 MB of RAM per 1 GB of LSFS device with enabled deduplication.
  9. Which sector size do I specify for LSFS device in StarWind management console?
    • 4KB sector size if used in Hyper-V environment, 512 B if used in VMWare environment (for compatibility reasons), in all other cases 4 KB is preferable .
  10. What will happen if LSFS device cannot find enough space to put segment file on the disk?
    • Device will be put in read-only mode.
  11. I am using build older than 8.0.7929 and my LSFS device ate up all disk space. What do I do?
    • Please contact StarWind support department at
  12. Is it possible to change size of my LSFS device?
    • Unfortunately, no, currently this feature is not supported.
  13. What is the maximum size of LSFS device?
    • Maximum size of LSFS device is 64 TB.

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