Is devicemapper a union filesystem?

[jude m]

Hello All,

Based on my initial reads it is quite evident that Docker heavily rely on Union Filesystem. My question is, is device mapper also a union file system?

Can some one please help me with some good pointers that will help me understand various file systems?

Thanks,

- J

[Jérôme Petazzoni]

Hi,

"Device Mapper" in the context of Docker means "Device Mapper Thin Provisioning Snapshots".

You can read more about it here: https://www.kernel.org/doc/Documentation/device-mapper/thin-provisioning.txt

It implements copy-on-write at the block level (as opposed to AUFS or overlayfs which implement it at the file level).

HTH,

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