The Background – Linux as a Fast Follower and the Need for Hot Patching
No doubt about it, Linux has made impressive strides in the last 15 years, gaining many features previously associated with high-end proprietary Unix as it made the transition from small system plaything to core enterprise processing resource and the engine of the extended web as we know it. Along the way it gained reliable and highly scalable schedulers, a multiplicity of efficient and scalable file systems, advanced RAS features, its own embedded virtualization and efficient thread support.
As Linux grew, so did supporting hardware, particularly the capabilities of the ubiquitous x86 CPU upon which the vast majority of Linux runs today. But the debate has always been about how close Linux could get to “the real OS”, the core proprietary Unix variants that for two decades defined the limits of non-mainframe scalability and reliability. But “the times they are a changing”, and the new narrative may be “when will Unix catch up to Linux on critical RAS features like hot patching”.
Hot patching, the ability to apply updates to the OS kernel while it is running, is a long sought-after but elusive feature of a production OS. Long sought after because both developers and operations teams recognize that bringing down an OS instance that is doing critical high-volume work is at best disruptive and worst a logistical nightmare, and elusive because it is incredibly difficult. There have been several failed attempts, and several implementations that “almost worked” but were so fraught with exceptions that they were not really useful in production.[i]
[Apologies to all who have just read this post with a sense of deja-vue. I saw a typo, corrected it and then republished the blog, and it reset the publication date. This post was originally published several months ago.]
Having been away from the Linux scene for a while, I recently took a look at a newer version of Linux, SUSE Enterprise Linux Version 11.3, which is representative of the latest feature sets from the Linux 3.0 et seq kernel available to the entre Linux community, including SUSE, Red Hat, Canonical and others. It is apparent, both from the details on SUSE 11.3 and from perusing the documentation on other distribution providers, that Linux has continued to mature nicely as both a foundation for large scale-out clouds as well as a strong contender for the kind of enterprise workloads that previously were only comfortable on either RISC/UNIX systems or large Microsoft Server systems. In effect, Linux has continued its maturation to the point where its feature set and scalability begin to look like a top-tier UNIX from only a couple of years ago.
Among the enterprise technology that caught my eye:
Scalability – The Linux kernel now scales to 4096 x86 CPUs and up to 16 TB of memory, well into high-end UNIX server territory, and will support the largest x86 servers currently shipping.
I/O – The Linux kernel now includes btrfs (a geeky contraction of “Better File System), an open source file system that promises much of the scalability and feature set of Oracle’s popular ZFS file system including checksums, CoW, snapshotting, advanced logical volume management including thin provisioning and others. The latest releases also include advanced features like geoclustering and remote data replication to support advanced HA topologies.
On April 23, IBM rolled out the long-awaited POWER8 CPU, the successor to POWER7+, and given the extensive pre-announcement speculation, the hardware itself was no big surprise (the details are fascinating, but not suitable for this venue), offering an estimated 30 - 50% improvement in application performance over the latest POWER7+, with potential for order of magnitude improvements with selected big data and analytics workloads. While the technology is interesting, we are pretty numb to the “bigger, better, faster” messaging that inevitably accompanies new hardware announcements, and the real impact of this announcement lies in its utility for current AIX users and IBM’s increased focus on Linux and its support of the OpenPOWER initiative.
OK, so we’re numb, but it’s still interesting. POWER8 is an entirely new processor generation implemented in 22 nm CMOS (the same geometry as Intel’s high-end CPUs). The processor features up to 12 cores, each with up to 8 threads, and a focus on not only throughput but high performance per thread and per core for low-thread-count applications. Added to the mix is up to 1 TB of memory per socket, massive PCIe 3 I/O connectivity and Coherent Accelerator Processor Interface (CAPI), IBM’s technology to deliver memory-controller-based access for accelerators and flash memory in POWER systems. CAPI figures prominently in IBM’s positioning of POWER as the ultimate analytics engine, with the announcement profiling the performance of a configuration using 40 TB of CAPI-attached flash for huge in-memory analytics at a fraction of the cost of a non-CAPI configuration.[i]
A Slam-dunk for AIX users and a new play for Linux
Nathan Bedford Forrest, a Confederate general of despicable ideology and consummate tactics, spoke of “keepin up the skeer,” applying continued pressure to opponents to prevent them from regrouping and counterattacking. POWER7+, the most recent version of IBM’s POWER architecture, anticipated as a follow-up to the POWER7 for almost a year, was finally announced this week, and appears to be “keepin up the skeer” in terms of its competitive potential for IBM POWER-based systems. In short, it is a hot piece of technology that will keep existing IBM users happy and should help IBM maintain its impressive momentum in the Unix systems segment.
For the chip heads, the CPU is implemented in a 32 NM process, the same as Intel’s upcoming Poulson, and embodies some interesting evolutions in high-end chip design, including:
Use of DRAM instead of SRAM — IBM has pioneered the use of embedded DRAM (eDRAM) as embedded L3 cache instead of the more standard and faster SRAM. In exchange for the loss of speed, eDRAM requires fewer transistors and lower power, allowing IBM to pack a total of 80 MB (a lot) of shared L3 cache, far more than any other product has ever sported.
This week the California courts handed down a nice present for HP — a verdict confirming that Oracle was required to continue to deliver its software on HP’s Itanium-based Integrity servers. This was a major victory for HP, on the face of it giving them the prize they sought — continued availability of Oracle’s eponymous database on their high-end systems.
However, HP’s customers should not immediately assume that everything has returned to a “status quo ante.” Once Humpty Dumpty has fallen off the wall it is very difficult to put the pieces together again. As I see it, there are still three major elephants in the room that HP users must acknowledge before they make any decisions:
Oracle will appeal, and there is no guarantee of the outcome. The verdict could be upheld or it could be reversed. If it is upheld, then that represents a further delay in the start date from which Oracle will be measured for its compliance with the court ordered development. Oracle will also continue to press its counterclaims against HP, but those do not directly relate to the continued development or Oracle software on Itanium.
Itanium is still nearing the end of its road map. A reasonable interpretation of the road map tea leaves that have been exposed puts the final Itanium release at about 2015 unless Intel decides to artificially split Kittson into two separate releases. Integrity customers must take this into account as they buy into the architecture in the last few years of Itanium’s life, although HP can be depended on to offer high-quality support for a decade after the last Itanium CPU rolls off Intel’s fab lines. HP has declared its intention to produce Integrity-level x86 systems, but OS support intentions are currently stated as Linux and Windows, not HP-UX.
There has been a lot of ill-considered press coverage about the “death” of UNIX and coverage of the wholesale migration of UNIX workloads to LINUX, some of which (the latter, not the former) I have contributed to. But to set the record straight, the extinction of UNIX is not going to happen in our lifetime.
While UNIX revenues are not growing at any major clip, it appears as if they have actually had a slight uptick over the past year, probably due to a surge by IBM, and seem to be nicely stuck around the $18 - 20B level annual range. But what is important is the “why,” not the exact dollar figure.
UNIX on proprietary RISC architectures will stay around for several reasons that primarily revolve around their being the only close alternative to mainframes in regards to specific high-end operational characteristics:
Performance – If you need the biggest single-system SMP OS image, UNIX is still the only realistic commercial alternative other than mainframes.
Isolated bulletproof partitionability – If you want to run workload on dynamically scalable and electrically isolated partitions with the option to move workloads between them while running, then UNIX is your answer.
Near-ultimate availability – If you are looking for the highest levels of reliability and availability ex mainframes and custom FT systems, UNIX is the answer. It still possesses slight availability advantages, especially if you factor in the more robust online maintenance capabilities of the leading UNIX OS variants.
Last year I wrote about Oracle’s new plans for SPARC, anchored by a new line of SPARC CPUs engineered in conjunction with Fujitsu (Does SPARC have a Future?), and commented that the first deliveries of this new technology would probably be in early 2012, and until we saw this tangible evidence of Oracle’s actual execution of this road map we could not predict with any confidence the future viability of SPARC.
The T4 CPU
Fast forward a year and Oracle has delivered the first of the new CPUs, ahead of schedule and with impressive gains in performance that make it look like SPARC will remain a viable platform for years. Specifically, Oracle has introduced the T4 CPU and systems based on them. The T4, an evolution of Oracle’s highly threaded T-Series architecture, is implemented with an entirely new core that will form the basis, with variations in number of threads versus cores and cache designs, of the future M and T series systems. The M series will have fewer threads and more performance per thread, while the T CPUs will, like their predecessors, emphasize throughput for highly threaded workloads. The new T4 will have 8 cores, and each core will have 8 threads. While the T4 emphasizes highly threaded workload performance, it is important to note that Oracles has radically improved single-thread performance over its predecessors, with Oracle claiming performance per thread improvements of 5X over its predecessors, greatly improving its utility as a CPU to power less thread-intensive workloads as well.
On June 15, HP announced that it had filed suit against Oracle, saying in a statement:
“HP is seeking the court’s assistance to compel Oracle to:
Reverse its decision to discontinue all software development on the Itanium platform
Reaffirm its commitment to offer its product suite on HP platforms, including Itanium;
Immediately reset the Itanium core processor licensing factor consistent with the model prior to December 1, 2010 for RISC/EPIC systems
HP also seeks:
Injunctive relief, including an order prohibiting Oracle from making false and misleading statements regarding the Itanium microprocessor or HP’s Itanium-based servers and remedying the harm caused by Oracle’s conduct.
Damages and fees and other standard remedies available in cases of this nature.”
Oracle announced today that it is going to cease development for Itanium across its product line, stating that itbelieved, after consultation with Intel management, that x86 was Intel’s strategic platform. Intel of course responded with a press release that specifically stated that there were at least two additional Itanium products in active development – Poulsen (which has seen its initial specifications, if not availability, announced), and Kittson, of which little is known.
This is a huge move, and one that seems like a kick carefully aimed at the you know what’s of HP’s Itanium-based server business, which competes directly with Oracle’s SPARC-based Unix servers. If Oracle stays the course in the face of what will certainly be immense pressure from HP, mild censure from Intel, and consternation on the part of many large customers, the consequences are pretty obvious:
Intel loses prestige, credibility for Itanium, and a potential drop-off of business from its only large Itanium customer. Nonetheless, the majority of Intel’s server business is x86, and it will, in the end, suffer only a token loss of revenue. Intel’s response to this move by Oracle will be muted – public defense of Itanium, but no fireworks.
This week at ISSCC, Intel made its first detailed public disclosures about its upcoming “Poulson” next-generation Itanium CPU. While not in any sense complete, the details they did disclose paint a picture of a competent product that will continue to keep the heat on in the high-end UNIX systems market. Highlights include:
Process — Poulson will be produced in a 32 nm process, skipping the intermediate 45 nm step that many observers expected to see as a step down from the current 65 nm Itanium process. This is a plus for Itanium consumers, since it allows for denser circuits and cheaper chips. With an industry record 3.1 billion transistors, Poulson needs all the help it can get keeping size and power down. The new process also promises major improvements in power efficiency.
Cores and cache — Poulson will have 8 cores and 54 MB of on-chip cache, a huge amount, even for a cache-sensitive architecture like Itanium. Poulson will have a 12-issue pipeline instead of the current 6-issue pipeline, promising to extract more performance from existing code without any recompilation.
Compatibility — Poulson is socket- and pin-compatible with the current Itanium 9300 CPU, which will mean that HP can move more quickly into production shipments when it's available.