An initial evaluation of 6Stor, a dynamically scalable IPv6-centric distributed object storage system

Precise architecture description and first benchmark results


The exponentially growing demand for storage puts a huge stress on traditional distributed storage systems. Historically, I/Ops (Inputs/Outputs per second) of hard drives have been the main limitation of storage systems. With the rapid deployment of solid state drives (SSDs) and the expected evolutions of their capacities, price and performance, we claim that CPU and network capacities will become bottlenecks in the future. In this context, we introduce 6Stor, an innovative, software-defined distributed storage system fully integrated with the networking layer. This storage system departs from traditional approaches in two manners: it leverages IPv6 new capabilities to increase the efficiency of its data plane—notably by using directly UDP and TCP rather than HTTP—and thus its performance; and it circumvents scalability limitations of other distributed systems by using a fully distributed metadata layer of indirection to offer flexibility. In this paper, we introduce and describe in details the architecture of 6Stor, with an emphasis on dynamic scalability and robustness to failure. We also present a testbed that we use to evaluate our novel approach by using Ceph—another well known distributed storage system—as baseline. Results obtained on an extensive testbed are presented and some initial conclusions are drawn.

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    Agents can be colocated on the same server. For example, monitors can also act as gateways but don’t function properly when located with OSDs. There are typically multiple OSDs per server corresponding to different storage devices.

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    Erasure Coding schemes are being investigated to greatly reduce the storage overhead but are not yet fully integrated to our 6Stor prototype. However, most of the architecture would work exactly the same way with encoded fragments instead of replicas.

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    In practice, the traditionnal linux network stack does not allow to listen on an arbitrary prefix. So implementation-wise, we use the workaround of binding the socket to ANYADDR and creating a local route redirecting the prefix to the loopback interface. This way, the packet is sent to the loopback interface and matches the ANYADDR criteria. There is no MAC resolution issues as the servers are seen as next-hop routers in the routing tables.

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    UDP is used for metadata exchanges because they fit in one packet. It provides better latency and less computing overhead but requires a timeout to retransmit when losses happen.

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    The lower the parameters \(a_m\) and \(a_s\), the lesser delay before the client receives an acknowledgement that the object is written to the cluster but the lower reliability in case of simultaneous failures during the operation.

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    In the background, it is also possible to rebalance data from existing SNs to the new one. However, this is absolutely not mandatory and can be done object by object, without making any node or object replica unavailable as it is the case in some storage systems.

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    A quick handshake is being made before each replica transmission to avoid multiple retransmissions for the same object.

  8. 8.

    This is not totally true, as there need to be at most as many MNs as there are different addresses in the cluster metadata prefix, but in practice this number is in the order of millions of billions.


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Correspondence to Guillaume Ruty.

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Ruty, G., Rougier, J., Surcouf, A. et al. An initial evaluation of 6Stor, a dynamically scalable IPv6-centric distributed object storage system. Cluster Comput 22, 1123–1142 (2019).

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  • Distributed object storage
  • IPv6 centric networking
  • Software defined systems