PureStorage FlashArray systems are all solid-state systems, providing both FC and iSCSI block storage access. All data is both deduplicated and compressed prior to being written. Pure Storage claims there is no performance penalty for deduplicating and compressing data in-line, which enables an effective capacity ranging between 61 TB and 3.3 PB for their //X products and up to 5.2 PB for their //C product.
With FlashArray //X, Pure Storage has updated their second generation //m systems that continue to utilize purpose-built controller hardware and a custom NVRAM module. The system has dual controllers with either SAS attached SSDs or DirectFlash modules internal to the controllers and add-on device enclosures. In 2019, Pure Storage introduced the FlashArray//C system as a high capacity flash array utilizing QLC flash.
Evaluator Group Comment: Pure Storage marketing calls the controllers “active/active” but they are really active/passive in that both controllers cannot be actively transferring data between devices and hosts. The “expanded” definition of active/active used is because the standby controller keeps the host bus adapters active and allows selections to pass to the other controllers.
The FlashArray //X is an update of the controller hardware but the first that utilizes NVMe protocol and PCIe interfaces for custom designed flash modules called DirectFlash. DirectFlash can replace the use of standard SSDs in FlashArray //X, FlashArray //C, and previous //m systems are upgradable according to the guarantee made in the fall of 2016. Pure Storage claims a 4x performance improvement with the use of NVMe DirectFlash modules vs SSDs. The //X70 and //X90 can utilize a further performance increase by using Pure Storage’s DirectMemory cache. DirectMemory offers Optane SCM modules that can be used for read caching.
Use of NVRAM accelerates write performance by allowing the system to acknowledge a write and then coalesce data before storing it across solid-state drive modules.
The embedded “Purity OS” now at version 5.1 (FA5) has many advanced features including encryption, snapshots, and remote replication along with a vCenter web plugin and VMware VAAI support. Version 4.8 added a fairness algorithm called Always On QoS to eliminate the noisy neighbor problem and NPIV support for upgrades to redirect I/Os to ports. Version 5 added VVOL support, improved compression, active-active stretched cluster support, the ability to run VMs and containers on the storage platform, and portable snapshots including CloudSnap.
Dual controllers connected with Intel PCIe bridging provides HA, along with incremental performance due to round-robin volume access to host volumes over multiple paths. Capacity may be scaled by adding additional storage trays, with up to 4 trays. Pure Storage increases the effective capacity with deduplication and compression and achieves an average data reduction ratio in excess of 5:1 according to field data.
Incoming data is written to NVRAM, and mirrored to the partner controller in HA configurations. Next, a write acknowledgement is sent to the client. A unique hash is created from the data and then stored at the address of its computed hash. This two-tiered write caching helps to alleviate host visible write delays encountered from SSD devices when performing garbage collection.
By storing data at an address dependent upon its content data is deduplicated, with duplicate data stored at the same address. Finally, data is de-staged to flash in batches of several megabytes at a time. Each flash module is enabled to either read or write data, but not both simultaneously, since that can have a performance impact.
Three copies of metadata are stored with dual parity protection, providing high data integrity. Additionally, read requests are possible from partial RAID stripe reads, by reconstructing data inline if sufficient data has been read.
The Pure Storage //X systems are designed as a general purpose, high performance storage system competing with other mid and high range storage systems. Target applications are those requiring high performance without a large capacity requirement.
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Pure Storage FlashArray was designed as an all-flash system using commodity servers and SSDs. As one of the early flash systems to market, Pure Storage has done well with systems that provide good performance with modest capacity, increased by software-implemented compression and deduplication. Pure Storage has also continued to develop the system with improved features and adding support for NVMe and PCIe attached devices, with a 4x performance improvement according to Pure Storage information.