Last year Intel introduced the P3700, P3600 and P3500 series, the first SSDs with the PCI-Express interface that combined four lanes with the modern NVMe protocol. This combination means that these professional SSDs are capable of higher speeds than the conventional Serial ATA and AHCI models. We tested the 400GB variant of the P3700 series.
A high-end PC without an SSD is almost unthinkable and SSDs are taking the place of the old hard disk in servers as well. The considerably better performance of SSDs when it comes to read and write commands, but as well as with random workloads, mean that changing HDDs to SSDs can give a significant boost in performance for a lot of server tasks. Certainly web servers – where a lot of clients access a lot of small files simultaneously – and database servers – where there are a lot of random read- and write commands – can benefit a great deal by using SSDs. We can confirm this from our own experience with the servers of Hardware.Info.
Most server SSDs up until now come in 2.5” size and use the Serial ATA interface, the same as a regular computer would. This is because by using an existing form factor and interface the SSDs are a drop-in replacement for regular hard disks. However Serial ATA, including SATA600, is a limiting factor for SSDs. The interface is limited to 600 MB/s, in practice this mostly means 550 MB/s. Modern SSDs can reach these speeds easily by using multiple parallel flashchips. Because Serial ATA 1200 is not in the making SSD manufacturers are looking at PCI-Express as new interface. PCI-Express 3.0 with two lanes can manage speeds of up to 2 GB/s, PCI-Express 3.0 x4 can reach 4 GB/s.
PCI-Express 3.0 x4 can reach speeds of up to 4000 MB/s.
However the SATA-interface is not the only bottleneck. The used AHCI protocol was made in a time before SSDs were a thing and is not meant for storage with low latency that is suitable for the parallel processing of a lot of I/O-transactions. Because of this about everyone that has some involvement in the SSD market came together to release a successor to AHCI called NVMe in 2011. NVMe offers a lot of advantages when compared to AHCI. For starters the CPU-overhead is a lot less. For example when using Linux a single I/O operation costs about 26,000 CPU-cycles for AHCI. NVMe does the same in 10,000 I/O cylces. A modern quad-core processor with its 400,000 Iops would be fully charged with managing the storage, when using NVMe a single core should be able to do the same.
The Intel P3700, P3600 and P3500 SSDs use PCI-Express 3.0 x4 as interface. While certainly not the first PCI-Express based SSDs a lot of other solutions were basically using a SATA RAID-controller in combination with multiple conventional SATA SSD-controllers, all brought together. The Intel P-series SSDs come equipped with a native PCIe x4 controller and are the first that are suited for NVMe. The controller is capable of high performance, for one because it can manage up to 18 flashchips. SATA SSD-controllers in comparison only go up to 8 channels.
To be able to use the SSD the server does not have to meet certain requirements, although a relatively modern operating system is needed. Microsoft supports NVMe from Windows 8.1 and Windows Server 2012 R2. Linux has built-in support since kernel-version 3.10. If you want to use it to boot from you need an UEFI BIOS that is compatible with UEFI 2.3.1 or higher. These SSDs will presumably be used as secondary storage, for example the storing of data. Being able to boot is of no importance in this case. If you do want to boot using one of these SSDs you should take a look at the manual of the server and / or motherboard to find out if you can boot using NVMe-based devices.