Tuesday, June 19, 2018

Hybrid Storage Pools

Using Hybrid Storage Pools:

 Most of the storage available on the market today utilizes a small amount of NRAM devices (usually 1, 8 or even 16GB in size) as the first cache tier of the system and also hard disk drivers. NRAM devices are expensive, and disk drivers’ performance is affected by seek operations, rotation and transfer times, which can result in I/O bottleneck and performance problems. Oracle ZFS Storage Appliance implements a Hybrid Storage Pool architecture designed to work with multiple tiers of storage media to maximize the performance for the virtualized environment.

First Tier: DRAM (large L1 cache) – DRAM memory and high-optimized and low-latency solid state disks combined with ZFS file systems architecture (ReadZilla) accelerate read-cache operations for the virtualized environment. Unlike traditional NAS architecture, Oracle ZFS Storage Appliance and its Hybrid Storage Pools utilize DRAM devices as the main cache device of the system. DRAM devices are cheaper, faster and deliver higher performance than NVRAM, so they are well matched for random I/O workloads – the kind of workloads performed by hypervisors/virtualized environments. DRAM devices are also used by the Adaptive Replacement Cache (ARC), which is part of the ZFS file system architecture model and intelligently managed by instructions provided by multiple cache algorithms.

Second Tier: SSDs (large L2 cache) – High-optimized and low-latency solid state disks combined with ZFS file systems log architecture (ZIL or LogZilla) to accelerate write-cache operations. These provide excellent performance and fast response for writing operations performed by applications and databases running in virtualized environment. The Hybrid Storage Pools are SSD devices designed to provide fast writing operations (100 times faster than traditional disk drivers) with low latency. Inside of the Hybrid Storage Pool architecture, SSD devices host the ZFS ZIL log (known as LogZilla or ZFS Intent Log), which is part of the ZFS file system architecture and mainly responsible for accelerating the synchronous writing operations requested by the critical applications and databases running in virtualized environments. Also, the SSDs are utilized by the Layer 2 Adaptive Replacement Cache (L2ARC), which is an extension of the ARC (main cache of the system) and hosts the read log devices for the ZFS architecture.

Third Tier: Disk Pools – Disk pools are composed of high-performance (15000 rpm) and/or high capacity (7200 rpm) disks that are protected by different RAID levels and intelligently managed by the ZFS file system. Disk pools are designed to archive the application data, providing continuously high I/O rates for different types of workloads, even when utilizing high-capacity disks (7200 rpm). Disk pools can optionally be configured with 15000 rpm disks, which provide the highest performance and thousands of IOPS for datastores typical of virtualized environments.

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