Sizing and Partitioning Strategies for Burst-Buffers to Reduce IO Contention

Dimensionnement de Burst-Buffers pour réduire la contention Entrées-Sorties

Guillaume Aupy (1) , Olivier Beaumont (2) , Lionel Eyraud-Dubois (2)

1 TADAAM - Topology-Aware System-Scale Data Management for High-Performance Computing
2 Realopt - Reformulations based algorithms for Combinatorial Optimization

Burst-Buffers are high throughput and small size storage which are being used as an intermediate storage between the Parallel File System (Parallel File System) and the computational nodes of modern HPC systems. They can allow to hinder to contention to the Parallel File System, a shared resource whose read and write performance increase slower than processing power in HPC systems. A second usage is to accelerate data transfers and to hide the latency to the Parallel File System. In this paper, we concentrate on the first usage. We propose a model for Burst-Buffers and application transfers. We consider the problem of dimensioning and sharing the Burst-Buffers between several applications. This dimensioning can be done either dynamically or statically. The dynamic allocation considers that any application can use any available portion of the Burst-Buffers. The static allocation considers that when a new application enters the system, it is assigned some portion of the Burst-Buffers which cannot be used by the other applications until that application leaves the system and its data is purged from it. We show that the general sharing problem to guarantee fair performance for all applications is an NP-Complete problem. We give a polynomial time algorithms for the special case of finding the optimal buffer size such that no application is slowed down due to Parallel File System contention, both in the static and dynamic cases. Finally, we provide evaluations of our algorithms in realistic settings. We use those to discuss how to minimize the overhead of the static allocation of buffers compared to the dynamic allocation.

Nous nous intéressons à l’utilisation de Burst-Buffers en temps qu’espace de stockage intermédiaire entre les nœuds de calcul et le Système de Fichiers Parallèles (PFS). Ce dimensionnement peut être statique (à l’arrivée d’une application dans le système), ou dynamique (en fonction des demandes Entrées-Sorties). Nous montrons que le problème général de partager équitablement les buffers entre applications est NP-complet. Nous montrons que dans le cas particulier où l’on cherche à minimiser la taille totale du buffer pour qu’aucune application ne soit ralentie est résolvable en temps polynomial. Pour résoudre ce problème nous proposons un programme linéaire. Finalement nous proposons des évaluations à taille de buffer fixé pour montrer la performance de certains algorithmes naifs communs.

Domaines: Calcul parallèle, distribué et partagé [cs.DC]

Guillaume Aupy, Olivier Beaumont, Lionel Eyraud-Dubois. Sizing and Partitioning Strategies for Burst-Buffers to Reduce IO Contention. [Research Report] RR-9213, Inria. 2018. ⟨hal-01904032v2⟩