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swami
Asked: 2020-06-01 23:32:49 +0800 CST

How does an object store write objects to disk

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In an object storage solution, how is the object data actually written to the underlying storage volumes? i.e. In what format is it written? Does it use an intermediate file system, or does it access the block storage directly? Or is it different for each implementation?

Suppose I have some data stored on one on-premise object storage platform and I want to migrate them to another, by just pointing the application at the disks - not having to copy all the data over. example: ceph to minio. Would that be possible? i.e. do they use some standardized way of storing the underlying data?

What happens if I lose the object storage middleware and I just have the physical volumes (disks). Would I be able to retrieve or understand the data in any way?

Finally, can an object storage solution be based on tape volumes (since they are lower cost than disk)? Assuming that I'm not concerned about lower latency of having to load/unload tapes.

object-storage

1 Answers

  1. Best Answer

    In an object storage solution, how is the object data actually written to the underlying storage volumes?

    It really depends on the specific object storage software. For example, Ceph used to write object on top of XFS, but now uses the "BlueStore" backend (which is similar to an application-specific database, at least conceptually). A big difference between object storage systems is how they manage and store metadata vs data. For example, Gluster (which is not a "true" object storage system) does not use centralized metadata, while Ceph make heavy used of metadata processes/nodes.

    Suppose I have some data stored on one on-premise object storage platform and I want to migrate them to another, by just pointing the application at the disks - not having to copy all the data over. example: ceph to minio. Would that be possible?

    Generally no, unless you are using the very same source/destination object storage software (ie: you are only moving disks between identical systems)

    What happens if I lose the object storage middleware and I just have the physical volumes (disks). Would I be able to retrieve or understand the data in any way?

    You will lose all your data, unless you are using a metadata-less store (ie: Gluster). After all, it is similar to losing all dir/file info of a filesystem.

    Finally, can an object storage solution be based on tape volumes (since they are lower cost than disk)? Assuming that I'm not concerned about lower latency of having to load/unload tapes

    Some tape systems can provide a virtualized block device out of tapes, but it will have low performance and cause aggressive aging/stress on the tapes themselves (a thing to strongly avoid).

    In general, you can not improvise yourself as a "object storage admin" or even a classical "storage admin". You need to be well versed in the topic and have good practice on test machines/cases.

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