Comment (1) Visits (28197)
A client asked me to explain "Nearline storage" to them. This was easy, I thought, as I started my IBM career on DFHSM, now known as DFSMShsm for z/OS, which was created in 1977 to support the IBM 3850 Mass Storage System (MSS), a virtual storage system that blended disk drives and tape cartridges with robotic automation. Here is a quick recap:
Sadly, it appears a few storage manufacturers and vendors have been misusing the term "Nearline" to refer to "slower online" spinning disk drives. I find this [June 2005 technology paper from Seagate], and this [2002 NetApp Press Release], the latter of which included this contradiction for their "NearStore" disk array. Here is the excerpt:
Which is it, "online access" or "nearline storage"?
If a client asked why slower drives consume less energy or generate less heat, I could explain that, but if they ask why slower drives must have SATA connections, that is a different discussion. The speed of a drive and its connection technology are for the most part independent. A 10K RPM drive can be made with FC, SAS or SATA connection.
I am opposed to using "Nearlne" just to distinguish between four-digit speeds (such as 5400 or 7200 RPM) versus "online" for five-digit speeds (10,000 and 15,000 RPM). The difference in performance between 10K RPM and 7200 RPM spinning disks is miniscule compared to the differences between solid-state drives and any spinning disk, or the difference between spinning disk and tape.
I am also opposed to using the term "Nearline" for online storage systems just because they are targeted for the typical use cases like backup, archive or other reference information that were previously directed to nearline devices like automated tape libraries.
Can we all just agree to refer to drives as "fast" or "slow", or give them RPM rotational speed designations, rather than try to incorrectly imply that FC and SAS drives are always fast, and SATA drives are always slow? Certainly we don't need new terms like "NL-SAS" just to represent a slower SAS connected drive.
Comments (3) Visits (14828)
Fellow master inventor and blogger Barry Whyte (IBM) recounts the past 20 years of history in IT storage from his perspective in a series of blog posts. They are certainly worth a read:
In his last post in this series, he mentions that the amazingly successful IBM SAN Volume Controller was part of a set of projects:
"IBM was looking for "new horizon" projects to fund at the time, and three such projects were proposed and created the "Storage Software Group". Those three projects became know externally as TPC, (TotalStorage Productivity Center), SanFS (SAN File System - oh how this was just 5 years too early) and SVC (SAN Volume Controller). The fact that two out of the three of them still exist today is actually pretty good. All of these products came out of research, and its a sad state of affairs when research teams are measured against the percentage of the projects they work on, versus those that turn into revenue generating streams."
But this raises the question: Was SAN File System just five years too early?
IBM classifies products into three "horizons"; Horizon-1 for well-established mature products, Horizon-2 was for recently launched products, and Horizon-3 was for emerging business opportunities (EBO). Since I had some involvement with these other projects, I thought I would help fill out some of this history from my perspective.
Back in 2000, IBM executive [Linda Sanford] was in charge of IBM storage business and presented that IBM Research was working on the concept of "Storage Tank" which would hold Petabytes of data accessible to mainframes and distributed servers.
In 2001, I was the lead architect of DFSMS for the IBM z/OS operating system for mainframes, and was asked to be lead architect for the new "Horizon 3" project to be called IBM TotalStorage Productivity Center (TPC), which has since been renamed to IBM Tivoli Storage Productivity Center.
In 2002, I was asked to lead a team to port the "SANfs client" for SAN File System from Linux-x86 over to Linux on System z. How easy or difficult to port any code depends on how well it was written with the intent to be ported, and porting the "proof-of-concept" level code proved a bit too challenging for my team of relative new-hires. Once code written by research scientists is sufficiently complete to demonstrate proof of concept, it should be entirely discarded and written from scratch by professional software engineers that follow proper development and documentation procedures. We reminded management of this, and they decided not to make the necessary investment to add Linux on System z as a supported operating system for SAN file system.
In 2003, IBM launched Productivity Center, SAN File System and SAN Volume Controller. These would be lumped together with Horizon-1 product IBM Tivoli Storage Manager and the four products were promoted together as the inap
The SAN File System was the productized version of the "Storage Tank" research project. While the SAN Volume Controller used industry standard Fibre Channel Protocol (FCP) to allow support of a variety of operating system clients, the SAN File System required an installed "client" that was only available initially on AIX and Linux-x86. In keeping with the "open" concept, an "open source reference client" was made available so that the folks at Hewlett-Packard, Sun Microsystems and Microsoft could port this over to their respective HP-UX, Solaris and Windows operating systems. Not surprisingly, none were willing to voluntarily add yet another file system to their testing efforts.
Barry argues that SANfs was five years ahead of its time. SAN File System tried to bring policy-based management for information, which has been part of DFSMS for z/OS since the 1980s, over to distributed operating systems. The problem is that mainframe people who understand and appreciate the benefits of policy-based management already had it, and non-mainframe couldn't understand the benefits of something they have managed to survive without.
(Every time I see VMware presented as a new or clever idea, I have to remind people that this x86-based hypervisor basically implements the mainframe concept of server virtualization introduced by IBM in the 1970s. IBM is the leading reseller of VMware, and supports other server virtualization solutions including Linux KVM, Xen, Hyper-V and PowerVM.)
To address the various concerns about SAN File System, the proof-of-concept code from IBM Research was withdrawn from marketing, and new fresh code implementing these concepts were integrated into IBM's existing General Parallel File System (GPFS). This software would then be packaged with a server hardware cluster, exporting global file spaces with broad operating system reach. Initially offered as IBM Scale-out File Services (SoFS) service offering, this was later re-packaged as an appliance, the IBM Scale-Out Network Attached Storage (SONAS) product, and as IBM Smart Business Storage Cloud (SBSC) cloud storage offering. These now offer clustered NAS storage using the industry standard NFS and CIFS clients that nearly all operating systems already have.
Today, these former Horizon-1 products are now Horizon-2 and Horizon-3. They have evolved. Tivoli Storage Productivity Center, GPFS and SAN Volume Controller are all market leaders in their respective areas.
This week, Hitachi Ltd. announced their next generation disk storage virtualization array, the Virtual Storage Platform, following on the success of its USP V line. It didn't take long for fellow blogger Chuck Hollis (EMC) to comment on this in his blog post [Hitachi's New VSP: Separating The Wheat From The Chaff]. Here are some excerpts:
Chuck implies that neither Hewlett-Packard (HP) nor Hitachi Data Systems (HDS) as vendors provide any value-add from the box manufactured by Hitachi Ltd. so combines them into a single category. I suspect the HP and HDS folks might disagree with that opinion.
When I reminded Chuck that IBM was also a major player in the high-end disk space, his response included the following gem:
"Many of us in the storage industry believe that IBM currently does not field a competitive high-end storage platform. IDC market share numbers bear out this assertion, as you probably know."
While Chuck is certainly entitled to his own beliefs and opinions, believing the world is flat does not make it so. Certainly, I doubt IDC or any other market research firm has put out a survey asking "Do you think IBM offers a competitive high-end disk storage platform?" Of course, if Chuck is basing his opinion on anecdotal conversations with existing EMC customers, I can certainly see how he might have formed this misperception. However, IDC market share numbers don't support Chuck's assertion at all.
There is no industry-standard definition of what is a "high-end" or "enterprise-class" disk system. Some define high-end as having the option for mainframe attachment via ESCON and/or FICON protocol. Others might focus on features, functionality, scalability and high 99.999+ percent availability. Others insist high-end requires block-oriented protocols like FC and iSCSI, rather than file-based protocols like NAS and CIFS.
For the most demanding mission-critical mix of random and sequential workloads, IBM offers the [IBM System Storage DS8000 series] high-end disk system which connects to mainframes and distributed servers, via FCP and FICON attachment, and supports a variety of drive types and RAID levels. The features that HP and HDS are touting today for the VSP are already available on the IBM DS8000, including sub-LUN automatic tiering between Solid-State drives and spinning disk, called [Easy Tier], thin provisioning, wide striping, point-in-time copies, and long distance synchronous and asynchronous replication.
There are lots of analysts that track market share for the IT storage industry, but since Chuck mentions [IDC] specifically, I reviewed the most recent IDC data, published a few weeks ago in their "IDC Worldwide Quarter Disk Storage Tracker" for 2Q 2010, representing April 1 to June 30, 2010 sales. Just in case any of the rankings have changed over time, I also looked at the previous four quarters: 2Q 2009, 3Q 2009, 4Q 2009 and 1Q 2010.
(Note: IDC considers its analysis proprietary, out of respect for their business model I will not publish any of the actual facts and figures they have collected. If you would like to get any of the IDC data to form your own opinion, contact them directly.)
In the case of IDC, they divide the disk systems into three storage classes: entry-level, midrange and high-end. Their definition of "high-end" is external RAID-protected disk storage that sells for $250,000 USD or more, representing roughly 25 to 30 percent of the external disk storage market overall. Here are IDC's rankings of the four major players for high-end disk systems:
By either measure of market share, units (disk systems) or revenue (US dollars), IDC reports that IBM high-end disk outsold both HDS and HP combined. This has been true for the past five quarters. If a smaller start-up vendor has single digit percent market share, I could accept it being counted as part of Chuck's "occasional sideshow from other vendors trying to claim relevance", but IBM high-end disk has consistently had 20 to 30 percent market share over the past five quarters!
Not all of these high-end disk systems are connected to mainframes. According to IDC data, only about 15 to 25 percent of these boxes are counted under their "Mainframe" topology.
Chuck further writes:
"It's reasonable to expect IBM to sell a respectable amount of storage with their mainframes using a protocol of their own design -- although IBM's two competitors in this rather proprietary space (notably EMC and Hitachi) sell more together than does IBM."
The IDC data doesn't support that claim either, Chuck. By either measure of market share, units (disk systems) or revenue (US dollars), IDC reports that IBM disk for mainframes outsold all other vendors (including EMC, HDS, and HP) combined. And again, this has been true for the past five quarters. Here is the IDC ranking for mainframe disk storage:
IBM has over 50 percent market share in this case, primarily because IBM System Storage DS8000 is the industry leader in mainframe-related features and functions, and offers synergy with the rest of the z/Architecture stack.
So Chuck, I am not picking a fight with you or asking you to retract or correct your blog post. Your main theme, that the new VSP presents serious competition to EMC's VMAX high-end disk arrays, is certainly something I can agree with. Congratulations to HDS and HP for putting forth what looks like a viable alternative to EMC's VMAX.