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Enterprise Storage SelectionAn enterprise subsystem can be defined as one that supports all the major operating systems; z/OS, Unix variants, Linux variants, Windows and Netware. The major enterprise vendors are discussed below. The first section discusses the enterprise products from the five big enterprise vendors; EMC, HDS, IBM, SUN and HP. The second section is a table that compares their products. EMCHistoryEMC started out producing cache memory and developed solid state disks, memory devices that emulated spinning disks, but with much faster performance. These solid state disks were usually re-badged and sold by StorageTek. Around 1988, EMC entered the storage market in its own name, selling symmetrix disk subsystems with what at that time was a very large, 256MB cache fronting 24GB of RAID 1 storage. Their mosaic architecture was the first to map IBM CKD mainframe disk format to standard FBA open system backend disks, and as such, could claim to be the first big user of storage virtualisation. In those days, EMC developed a reputation for delivering best performance, but at a price. EMC introduced their latest addition to the symmetrix range, the V-MAX, in April 2009. This is the successor to the DMX-4, so is it just coincidence that 'V' is the Roman number for 5, as well as standing for Virtual? ArchitectureThe DMX series uses the Direct Matrix architecture, now called Enginuity. The principle behind Direct Matrix is that all IO comes into the box the front-end directors. These are connected to global memory cache modules, which are in turn connected to back-end directors that drive the IO down to the physical disks. This connectivity is all done by a directly connected, point-to-point fibre-channel matrix. There is no switching or bus arbitration involved. Each DMX-4 data path runs at 4GB/s, and there are 128 concurrent data paths. In 2008, EMC became the first to use flash storage in an enterprise subsystem, for high performance applications. The V-MAX architecture builds on the older DMX architecture. The first release of V-MAX consists of between 1 and 8 engines. Each engine is built from commodity processors, cache, host adapters and disk adapters. This makes them relatively cheap to produce and easier to upgrade later. Internally, the engine components communicate locally, so memory access is local. However, the engines must also communicate with each other and also support the Enginuity global memory concept. To achieve this, the memory is virtualised, and each engine communicates with other engines using fiber connect and RAPIDIO technology. When a director gets a memory request it then checks the location, and if it is local it is served at memory bus speeds. If it is remote, then the request is packaged up and sent off to the remote director for processing. Presumably EMC have optimised this setup to ensure that most memory accesses are local. Certainly the EMC diagrams show each engine with 2 directors, 16 host ports and 16 disk ports, but only 4 virtual matrix ports. There are two of these ports per director, and they are connected to other engines with two MIBE (Matrix Interface Boards). The Cache memory is mirrored, and in configurations with 2 or more engines, it is mirrored between engines. This architecture extends the direct matrix principle, but now the matrix is virtual. One of the difficulties in machine hall design is leaving room for various frames to grow as cabinets are added to increase capacity. The plan is that V-MAX frames do not need to be in the same footprint, they can be 100m apart. One interesting feature is the storage tiering, based on T0 Flash storage, T1 FC drives and T2 SATA drives. A new FAST (Fully Automated Storage Tiering) product will automate movement between tiers. Again, the devil will be in the detail. Will FAST move data at file level, block level or LUN level? Will it be driven by business policies? ModelsThe Symmetrix DMX-4 became generally available in August 2007. It is very scalable, from 240-2,400 drives. It supports 1 TB SATAII drives and 73 or 146GB flash drives. Internally, it uses 4Gb/s communications end to end, with 4 Gb/s support for FICON or Fibre Channel host connections, internal connectivity and Fibre Channel Drives. The backend architecture is FCAL. The V-MAX starts with the single-cabinet, entry-level Symmetrix V-MAX SE that can hold 120 disks. This can be extended by adding up to 10 more frames, each holding 240 disks. Note that in this first release, all the frames must be adjacent to each other. SoftwareDMX software includes EMC Symmetrix Management Console for defining and provisioning volumes and managing replication. The Time Finder products are used for in-subsystem and PIT replication, and SRDF for remote replication. SRDF can run in full PPRC compatibility mode, and can also replicate to three sites in a star configuration.
OpennessThe DMX in general is not an Open implementation. SRDF, for example, will only work between EMC devices, and even then, not with all of them. EMC Open Replicator has the ability to take PIT copies from selected non-EMC subsystems to DMX, or to copy from DMX to selected non-EMC devices.
Full FAST capability is planned for 2010, and full intersite connectivity is also planned, permitting a geographically dispersed storage subsystem, but no date is announced yet. HDSHistoryHitachi Data Systems was always known as the company that manufactured disks that were exactly compatible with IBM, but worked a little faster and cost a little less. HDS broke that mould when they introduced the 'Lightning' range of subsystems in 2000, which was a merging of telephony cross-bar technology and storage subsystem technology. They extended and developed that architecture further with the USP (Universal Storage Platform), released in September 2004. ArchitectureThe USP architecture is based on cross-bar switch connectivity, in-subsystem virtualisation, the ability to partition a subsystem into component LPARS and to ability to replicate data to externally attached subsystems.
ModelsThe enterprise USP comes in four models, with an entry level NSC55 device. Hardware wise, the newer USPV looks the same as a USP1100. The USP models are all cabinet mounted and differ in maximum cache size, number of array frames and so number of internal disks supported and number of cross-bar switches. The older USP devices can connect up to 32 Petabytes of external storage, at least in theory, while the USPV can connect up to 247 PB externally. It is possible to upgrade between USP models without requiring an outage.
SoftwareThe USP uses HiCommand to manage both disk and virtualisation configuration. Replication software is provided under an umbrella product called Business Continuity Manager. This is integrated into the HiCommand product which means that z/OS and Open Systems replication can all be managed and monitored from one point. The actual replication software includes ShadowImage (FlashCopy compatible) for in-subsystem replication, TrueCopy for remote synchronous and asynchronous replication and Universal Replicator for remote asynchronous replication. OpennessThe USP is an open architecture, in that it works with disks from many other vendors and virtualises the data. The list of supported vendors includes EMC, HP, IBM and SUN, as well as older HDS devices. In general, the USP will support the hardware, but replaces the OEM replication software with its own. IBMHistoryThe original IBM hard drive, the RAMAC 350, was manufactured in 1956, had a 24 inch (609mm) platter, and held 5 MB. The subsystem also weighed about 1 ton. That was a bit before my time, but when I joined IT 23 years ago, the storage market was dominated by IBM, the mainframe was king, and the standard disk type was the IBM 3380 model K which contained 1.89 GB. IBM lost their market leader position to EMC sometime in the 1990s. IBM introduced their latest subsystem family, the DSxxxx series, in late 2004 in response to competition from EMC and HDS. They updated their internal bus architecture to increase the internal transfer speed by 200% plus over the ESxxx series, and also abandoned their SSA disk architecture for a switched FC-AL standard. The DS8300 is essentially a follow-on from the ESS disk series, and re-uses much of the ESS microcode. ArchitectureThe DS8000 architecture effectively consists of two processor complexes called servers that are connected to hosts using host adaptors, and disks using device adaptors. The processor complex consists of 2-way or 4-way p-570 servers containing two types of cache, volatile and persistent memory. Every write IO is written to volatile memory in one processor, and non-volatile in the other before the write is acknowledged as complete. The subsystem effectively works internally as two separate units, but one server can run the whole subsystem if the other fails.
Internal connectivity between servers and device adaptors uses RI0-G connectors, the same as is used internally in the p-series servers. These links can run at a 2 GB per second sustained bandwidth and permit the sharing of host adapters between servers. Host adaptors can be either ESCON, or 4Gb/s FICON / FC. Each Host adaptor provides 4 Host connections, but has only two internal protocol engines, so there may be a degree of blocking. Device adaptors are installed in pairs, and include the RAID controllers. The device adaptors are connected to the disks using Switched FC-AL, but they are not in an FC-AL loop. The disks are allocated FC-AL addresses to allow the switching to work, but once the connection is made, communications are point-to-point Fibre Channel. For more detail, try http://www.redbooks.ibm.com/redpieces/pdfs/sg246786.pdf ModelsThe top range DS8300 is a cabinet mounted subsystem that can support a maximum of 1024 disk drives and will hold a maximum of 460 TB raw capacity using 500GB FATA disks, or 192 TB using 300GB FC disks. The base cabinet holds 128 disk drives, up to two expansion cabinets can be added, each holding 256 disk drives. The raw disks are supplied in blocks of sixteen, but are configured in groups of eight, with each group being called an array group. All the disks in an array group must have identical size and rotation speed. The DS8300 uses two four-way p-570 servers The DS8100 spec. is similar to the DS8300, except that it will only support one expansion frame, contains a maximum of 384 drives, and has a maximum raw capacity of 192 TB. The internal processor specification is also lower, at two dual processor p-570 servers. The DS8000 series currently has three Turbo models available: the DS8100 Turbo Model 931, and the DS8300 Turbo Models 932 and 9B2. The 931 and 932 models do not support LPARS, and have 2-way or 4-way processors respectively. The 9B2 model does support LPARS and has 4-way processors. The DS6800 is rack mounted, and supports up to 16 disk drives in the base unit. With seven expansion units, it can hold up to 128 drives, giving a maximum raw capacity of 38.4 TB with 300GB drives. SoftwareThe DS software includes Flashcopy for internal subsystem point-in-time data copies, IBM Total Storage DS Manager for configuration and Metro/Global mirror for continuous inter-subsystem data replication. The older ESS subsystems supported two kinds of z/OS Flashcopy, a basic version that just copied disks, and an advanced version that copied disks and files. DS only supports the advanced Flashcopy.
Remote mirroring versions include;
OpennessThe DS subsystem series is self contained and does not interface with any other vendor's storage subsystem. For Open Systems data, IBM does support mirroring and copying to other vendor's subsystems if they are fronted with SVC virtualisation. FuturesIBM promised a lot of enhancements to the DS series when they were first announced, and has delivered SATA drive support, space efficient Flashcopy, 4Gb FICON and virtual LUN space support so far.
HPHistoryI've always viewed HP as a major Intel player, but not a supplier with much of a presence in the mainframe market. I'm willing to change that view if someone can share their experiences. HP has been a Hitachi reseller for some time, but while they buy USP hardware from Hitachi, HP supplies its own software. ArchitectureBecause the HP XP24000 is a re-badged Hitachi USP, it has the same basic architecture. Older HP devices supported an extra CHIP set to provide more connectivity, but the latest models seems to use standard HDS hardware. ModelsHP now supplies two USP type models, the XP24000 and the XP20000, which are the equivalents of the USP V and the USP VM. SoftwareFor mainframe solutions, HP seems to supply standard HDS software. For Open Systems solutions, HP supplies its own software. This includes
OpennessThe XP24000 has the same open architecture as the HDS USP and supports the same range of OEM devices, plus it supports HP MSA devices. Oracle / SUNHistoryUntil recently, I've always considered SUN to be a midrange company that supplied storage for its server devices. While they have been Hitachi resellers for some time, they were never big in the enterprise market. However, SUN bought out StorageTek in June 2005 and StorageTek was an enterprise player. StorageTek was the first major company to put solid state cache in front of disks to make them perform better. In the late 1990s they brought out the Iceberg product. From an architectural perspective this box should have cleaned up the market with its innovative design and data management facilities. However even with IBM backing it was unable to really compete with the EMC 8xxx series and HDS 77xx series.
ArchitectureAs it is the same device, the SUN 9990 architecture is identical to the HDS USP. SUN is not mentioned in the comparison table below, but will have the same data as HDS. ModelsSUN has opted to resell the USP range as a single product, called the SUN Storedge 9990. They resell the NSC55 as the SUN Storedge 9985 SoftwareThe SUN Storedge 9990 runs the same HDS software as the USP OpennessAs the SUN 9990 is a re-badged HDS, it shares the same open architecture. NetappsNetApps is becoming one of the major Open Systems vendors. They specialise in the Intel market (Windows, Netware, Linux) and should be considered 'one to watch', rather than a current enterprise storage contender. Their hardware range includes the Network Appliance series, of which the FAS6070 is expandable up to 500TB. Their software range includes various SnapMirror and SnapClone products for inter subsystem and intra subsystem data copying. They have MSSQL, Oracle and Exchange agents. Storage Subsystem Features tableThe various suppliers of mainframe disks are contrasted in the tables below. The first row explains why the factor might be important, the second row just presents the facts, which were correct at time of writing, January 2009. However I'd advise you to check with your salesperson for up to date details.
Price is usually very negotiable, but be sure to make sure that the vendor quotes for a complete solution with no hidden extras. Also, make sure that you get capped capacity upgrade prices, including increased software charges as software is usually charged by capacity tiers. Copyright © Lascon Storage Ltd. 2000 to present date. By entering and using this site, you accept the conditions and limitations of use
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