Archive for the ‘Archive’ Category

Why Archive ?

November 22, 2010 3 comments


During a discussion I had at the SNIA blogfest, I mentioned that I’d written a whitepaper around archiving and I promised that I’d send it on. It took me a while to get around to this, but I finally dug it out from my archive, which is implemented in a similar way to the example policy at the bottom of this post.,  it only took me about a minute to search and retreive it once I’d started the process of looking for it from a FAS array that was far enough away from me to incur a 60ms RTT latency. Overall I was really happy with the result.

The document was in my archive because I wrote it almost two years ago, since then a number of things have changed, however the fundamental principals have not, I’ll work on updating this when things less busy, probably sometime around January ’11. On a final note, because I wrote this a couple of years ago when my job role was different than it is today, this document is considerably more “salesy” than my usual blog posts, it shouldnt be construed as a change in direction for this blog in general.


There are a number of approaches that can be broadly classified as some form of Archiving, including Hierarchical Storage Management (HSM), and Information Lifecycle Management (ILM).  All of these approaches aim to improve the IT environment by

  • Lowering Overall Storage Costs
  • Reducing the backup load and improving restore times
  • Improving  Application Performance
  • Making it easier to find and classify data

The following kinds of claims are common in the marketing material promoted by vendors of Archiving software and hardware

“By using Single Instance Storage, data compression and an ATA-based archival storage system (as opposed to a high performance, Fibre Channel device), the customer was able to reduce storage costs by $160,000 per terabyte of messages during the first three years that the joint EMC / Symantec solution was deployed. These cost savings were just the beginning, as the customers were also able to maintain their current management headcount despite a 20% data growth and the time it took to restore messages was drastically reduced. By archiving the messages and files, the customer was also able to improve electronic discovery retrieval times as all content is searchable by keywords.”

These kinds of results while impressive assume a number of things that are not true in NetApp implementations

  • A price difference between primary storage and archive storage of over $US160,000 per TB.
  • Backup and restores are performed from tape using bulk data movement methods
  • Modest increases in storage capacities require additional headcount

In many NetApp environments, the price difference between the most expensive tier of storage and the least expensive simply does not justify the expense and complexity of implementing an archiving system based on a cost per TB alone.

For file serving environments, many file shares can be stored effectively on what would be traditionally thought of as “Tier-3” storage with high-density SATA drives, RAID-6 and compression / deduplication. This is because unique NetApp technologies such as WAFL and RAID-DP provide the performance and reliability required for many file serving environments. In addition, the use of NetApp SnapVault replication based data protection, for backup and long term retention means that full backups are no longer necessary. The presence or absence of the kinds static data typically moved into archives has little or no impact on the time it takes to perform backups, or make data available in the case of disaster.

Finally, the price per GB and IOPS for NetApp storage has fallen consistently in line with the trend in the industry as a whole. Customers can lower their storage costs by purchasing and implementing storage only as required. NetApp FAS array’s ability to non-disruptively add new storage, or move excess storage capacity and I/O from one volume to the other within an aggregate makes this approach both easy, and practical.

While the benefits of archiving for NetApp based file serving environments may be marginal, archiving still has significant advantages for email environments, particularly Microsoft Exchange. The reasons for this are as follows

  1. Email is cache “unfriendly” and generally needs many dedicated disk spindles for adequate performance.
  2. Email messages are not modified after they have been sent/received
  3. There is a considerable amount of “noise” in email traffic (spam, jokes, social banter etc)
  4. Small Email Stores are easier to cache, which can significantly improve performance and reduce the hardware requirements for both the email servers and the underlying storage
  5. Email is more likely to be requested during legal discovery
  6. Enterprises now consider Email to be a mission critical application and some companies still mandate a tape backup of their email environments for compliance purposes.

Choosing the right Archive Storage

It’s about the application

EMC and NetApp take very different approaches to archive storage, each of which works well in a large number of environments. An excellent discussion on the details of this can be found in the NetApp whitepaper WP-7055-1008 Architectural Considerations for Archive and Compliance Solutions. For most people however, the entire process of archive is driven not at the storage layer, but by the archive applications. These applications do an excellent job of making the underlying functionality of the storage system transparent to the end user, however the user is still exposed to the performance and reliability of the storage underlying the archives.

Speed makes a difference

Centera was designed to be “Faster than Optical” and while it has surpassed this relatively low bar, its performance doesn’t come close to even the slowest NetApp array. This is important, because the amount of data that can be pushed onto the archive layer is determined not just by IT policy, but also by user acceptance and satisfaction with the overall solution. The greater the user acceptance, the more aggressive the archiving can be, which results in lower TCO and faster ROI.

Protecting the Archive

While the archive storage layer needs to be reliable, it should be noted that without the archive application and its associated indexes, the data is completely inaccessible, and may as well be lost. It might be possible to rebuild the indexes and application data from the information in the archive alone, often this process may be unacceptably long. Protecting the archive involves protecting the archive data store, the full text indexes, and the associated databases in a consistent manner at a single point in time.

Migrating from an Existing Solution

Many companies already have archiving solutions in place, but would like to change their underlying storage system to something faster and more reliable. Fortunately archiving applications build the capability to migrate date from one kind back-end storage to another into their software. The following diagrams show how this can be achieved for EmailXtender and DiskXtender to move data from Centera to NetApp.

Some organizations would prefer to completely replace their existing archiving solutions including hardware and software. For these customers NetApp collaborates with organizations such as Procedo (, to make this process fast and painless.


As mentioned previously, the cost and complexity of traditional archiving infrastructure may not add sufficient value to a NetApp file-serving environment, as many of the problems it solves are already addressed by core NetApp features. This does not mean that some form of storage tiering could not or should not be implemented on FAS to reduce the amount of NetApp primary capacity.

One easy way of doing this is by taking advantage of the flexibility of the built in backup technology. This is an extension of the “archiving” policy used by many customers, where the backup system is used for archive as well.  The approach of mixing backup and archive is rightly discouraged by most storage management professionals, the reasons for doing so in traditional tape based backup environments don’t apply.

The reasons for this are

  • Snapshot and replication based backups are not affected by capacity as only changed blocks are ever moved or stored
  • The backups are immediately available, and can be used for multiple purposes
  • Backups are stored on high reliability disk in space efficient manner using both non-duplication and de-duplication techniques
  • Files can be easily found via existing user interfaces such as Windows Explorer or external search engines

In general, SnapVault destinations use the highest density SATA drives with the most aggressive space savings policies applied to them. These policies and techniques, which may not be suitable for high performance file sharing environments, provide the lowest cost per TB of any NetApp offering. This combined with the ability to place the SnapVault destination in a remote datacenter may relieve the power, space and cooling requirements of increasingly crowded datacenters.

An example policy

Many companies file archiving requirements are straightforward, and do not justify the detailed capabilities provided by archiving applications. For example, a company might implement the following backup and archive policy

  • All files are backed up on a daily basis with daily recovery points kept for 14 days, weekly recovery points will be kept for two months and monthly recovery points kept for seven years.
  • Any file that has not been accessed in the last sixty days will be removed from primary storage and will need to be accessed from the archive

This is easily addressed in a SnapVault environment through the use of the following

  • Daily backups are transferred from the primary system to the SnapVault repository
  • Daily recovery points (snapshots) are kept on both the primary storage system and the SnapVault repository for 14 days
  • Weekly recovery points (snapshots) are kept only on the SnapVault repository
  • Monthly recovery points (snapshots) are kept only on the SnapVault repository
  • A simple shell script/batch file is executed after each successful daily backup which deletes any file from the primary volume that has not been accessed in thirty days
  • Users are allocated a drive mapping to their replicated directories on the SnapVault destination.
  • Optionally the Primary systems and SnapVault repository may be indexed by an application such as the Kazeon IS1200, or Google enterprise search.

Users then need to be informed that old files will be deleted after thirty days, and that they can access backups of their data, including the files that have been deleted from primary storage by looking through the drive that is mapped to the SnapVault repository, or optionally via the enterprise search engines user access tools.

By removing the files from primary storage, instead of the traditional “stub” approach favoured by many archive vendors, the overall performance of the system will be improved by reducing the metadata load, and users will be able to more easily find active files by having fewer files and directories on the primary systems.


Many Organisations archiving requirements can be met by simply adding additional SATA disk to the current production system replicated via SnapMirror to the current DR system – rather than managing separate archive platforms.

This architecture provides flexibility and scalability over time and reduces management overhead. Tape can also be used for additional backup and longer term storage if required. SnapLock provides the non-modifiable WORM like capability required of an archive without additional hardware (a software licensable feature, see more detail at ).

Categories: Archive, Data Protection, Value

Data Storage for ECM – Part 1 – Unified Storage

September 15, 2010 4 comments

The last few months have been interesting for me,  as my new job role involves a lot of work with alliance partners, many of whom either didn’t know anything about NetApp, or where they did know something it was along the lines of “Oh yeah, the NAS company”. In many respects, it’s a lot easier to explain what we do when someone has an open mind, as pre-conceived notions are often hard to budge, and telling someone they’re wrong is rarely a good way to start a trusted relationship. Even though I report up through our local director of marketing, my soul is still that of an engineer, so when it comes to describing what NetApp does, and why that’s important I tend to go straight to “Well, we still sell NAS, and that’s a big part of what we do, but we really sell is Unified Storage” at which point I expect to see the “and I should care about this because …” look

I’ve been seeing this look quite a bit recently, mostly because many of the people I speak to also get briefs from other storage vendors, and they too have suddenly started talking about “Unified Storage” without really understanding it or explaining its relevance to datacenter transformation. A good case in point was the opportunity I had to speak at the local VMware seminar series where I shared a stage with VMware, Cisco, and EMC. All of us got our 7.5 minutes  to explain how we helped accelerate our customers journey to the cloud. VMware went first, followed by EMC, then Cisco and then me..

I’d prepared two slides for my 7 minutes focussing on our key differentiators, Unified storage, tight VMware integration with advanced storage features, deduplication and storage efficiency, Secure Multi-Tenancy, Cisco validated designs, Backup and recovery, and waited happily to see if EMC would come out with their usual pitch.

Boy, was I surprised … EMC’s pitch was Unified storage, deduplication, tight VMware integration with advanced storage features, deduplication and  storage efficiency, security and Cisco validated designs … what the ????, had I suddenly slipped into a parallel universe ? Had EMC, a company fairly well known for pushing seven different kinds of storage with forklift upgrades  suddenly capitulated and acknowledged that the approach NetApp had been pushing for so many years was actually right ? Was Chuck Hollis about to come on stage and apologise for blatant manipulation of social media and comment filtering ?

Now while I could have picked holes in their story by pointing out that at least from a VMware perspective they don’t have deduplication, that their advanced integration with VAAI hadn’t been released, there was no Cisco Validated Design for vBlock, and that the RSA stuff had no integration at the storage layer, nobody is really interested in hearing vendors denigrate each other, and I only had 7 minutes to figure out how to show our unique ability to help customers in the face of the most shameless “me too” campaign I’ve ever seen.  During that 7 minutes there was one thing that really struck me. EMC has no real concept of why unified storage is important. Their concept of unified storage was something that allowed connection by Fibre Channel, iSCSI, CIFS and NFS and had a nice GUI. Having worked at NetApp for a number of years, I was surprised at how they’d missed the point completely. Almost everyone at NetApp knows that these are good features to have (we’ve had them for over 10 years now), but we also know that by themselves, they have only limited benefits. I’ve had a little while now to think about this, and it’s become clear to me that for other vendors, Unified storage is not a strategic direction, but a tactical response to NetApp’s continued success in gaining market share. This becomes even more obvious by taking a look at their storage portfolios

Entry Level NAS / NAS Gateway FAS Iomega Windows Storage Server Windows Storage Server N-Series (OEM) Windows Storage Server
Entry Level SAN / iSCSI FAS Celerra NX Equallogic MSA 


N-Series (OEM) 

DS3xxx (OEM)

MidRange NAS FAS Celerra NS Celerra (OEM) Polyserve ? N-Series (OEM) BlueArc(OEM)
Mid-Range SAN FAS CLARiiON Equallogic 

Celerra (OEM)




DS4xxx/5xxx (OEM) 

N-Series (OEM)


Archive & Compliance FAS Centera Centera (OEM) HP RISS FAS HCP
Backup to disk platform FAS DataDomain 



HP Sepaton (OEM)

Diligent VTL Dilligent (OEM)
Storage Virtualisation Gateway FAS (V-Series) Invista 



N-Series Gateway (OEM)

Object Repository StorageGRID Atmos StorageGRID (OEM) StorageGRID (OEM) HCP
High End  / Scale Out FAS / FAS (C-Mode) V-Max V-Max (OEM) USP-V (OEM) DS6xxx/8xxx 


Mainframe N/A V-Max V-Max (OEM) USP-V (OEM) DS8xxx 



Now, if you match one of those arrays against the workload they were designed for, you’ll probably get a pretty good result. In a static, reasonably predictable environment without much change, you could make a reasonable argument that this was the best approach to take. You built a silo around an application or function, and purchased the equipment that matched that function. I’ve seen more than one customer that had every product in a vendors portfolio, and seem to be fairly happy, or at least have been until fairly recently.

The problem with these narrow silo’ed approaches is that each silo creates new inefficiencies and dedicated areas of whitespace in both capacity, performance. For example, there is no way of taking excess capacity allocated to a  backup to disk appliance and start using it for CIFS home directories, nor is there a way of taking the excess IOPS capability of temporarily idle disk archive and allocate those IOPS to another application undergoing an unusual workload spike such as a VDI bootstorm.

But for me, the biggest area of waste is that of management. Each of these silo’s tends to get its own set of administrators and workflows, each of which may, or may not work in harmony with the other. Most of us have experienced the bitterness and waste of IT turf wars, and the traditional vendors not only encourage, but depend on and help  maintainin these functionality silos, as it allows a divide and conquer sales model that benefits the vendor far more than the customer. If there was a book entitled “How to build an inflexible and wasteful IT infrastructure”, I imagine that encouraging and spreading “IT functionality silos” would fill up the first few chapters. Even though there are a bunch of people who have been quite happy with this status quo, and the business processes from budgeting and product selection all the way through to procurement and training that entrenches this model, things are changing, and they’re changing a lot faster than I thought they would.

A lot of credit for this change has to go to vendors like Microsoft, Cisco and VMware whose products have blurred the lines of these traditional silos. Virtualisation at both the compute and network layers have driven the kinds of cross functional change CIO’s have been crying out for, and in the wake of this, Unified storage finds its natural fit ; not because of its support multiple protocols, but because these environments require the kind of  workload agility and managment simplicity that only a truly Unified storage offering can fully satisfy.

But it’s not just server and desktop virtualisation and other forms of shared infrastructure where unified storage is a natural fit. Almost any “multi-part” or landscape style application can benefit too, not just because of the flexibility and efficiency, but more importantly because of the fact that these environments are really hard to protect effectively. A really good example of this is Enterprise Content Management Applications such as FileNet and SharePoint

Typically these applications have

  • Content Servers
  • Business Process Workflow Engines / Servers
  • Database servers
  • Index Servers
  • Content Servers

In a large installation, there will be many of these servers and multiple databases, indexes and content repositories to cater for scalability and in some cases, the tyranny of distance (latency is forever).

In a “traditional” silo’d model this data would be stored on two or possibly three different kinds of storage arrays, each with its own method of backup and replication, most of which depend on some form of “bulk copy” backup method as the primary form of logical data protection. The effect of this is that backing up these ECM systems on traditional storage architectures is almost impossible. While I’ve been talking to customers about this for a few years, recently there seems to have been a big increase in customers seeing these problems. In one case a design review for a Petabyte scale SharePoint implementation identified that if a critical index was lost the entire infrastructure would be effectively unrecoverable, and that there was no effective backup capability. In another discussion I had today around redesigning data protection, a brief mention on ECM created more interest than almost anything else simply because of the difficulty of backing their Documentum system.

Truly unified storage not only allows data to be stored using multiple protocols, and provides rich functionality like deduplication and compliant WORM storage which makes it a logical choice for  ECM solutions, but more importantly it also provides a single integrated method for protecting that data in a way that is application-consistent without the need for a “cold” backup. And, you guessed it, NetApp can do that with ease, whereas other vendors’ versions of what they are calling unified storage would find that challenging (to be kind).

In the next few posts, I’ll take a deeper dive into exactly what NetApp does for Enterprise Content Management, with a focus on why Unified Storage is such a good match, and what we do to protect a company’s most important data assets.

Categories: Archive, Data Protection, Value

Backup Is Evil – Part 3 – Using Tape for Archives

April 3, 2010 Leave a comment

Why tape may be unsuitable for long term archiving

Other than the difficulty of expunging data which should no longer be kept, tape is a poor choice for long term archives for two other reasons. The first is that the Commonwealth and State Electronic Transactions Acts for the legal requirements for electronic transactions, and archiving procedures for electronic records state that data retention methods must allow for changes in technology. Tape has a poor track record in meeting this requirement, where for example data recorded on a “DLT III” tape cartridge which was still widely used less then 6 years ago, cannot be read by any commercially available tape drive today

Secondly “For any information kept in electronic form, the method of generating the information must provide a reliable way of maintaining the integrity of the information, unless a specific storage device is provided for by the relevant legislation.” [3]. Tape is a relatively delicate contact media, which degrades with use, can become physically damaged and is adversely affected by swings in environmental conditions. Data stored on tape can also be lost from exposure to magnetic fields. Thus, in order to provide “a reliable way of maintaining the integrity of the information” tapes must be periodically refreshed (read and rewritten). Managing refresh cycles for hundreds of tapes written over many years is a complex and an extremely costly task with potentially serious consequences if not managed properly.

Is tape really capable of keeping data for long periods of time ?

Some tape media such as LTO-4 is often touted as having a 30 year archival life. For a technology that is less than three years old, this kind of claim can only be relied upon through a fair degree of faith in the vendors’ statistical analysis techniques. IT and business management are asked to take this leap of faith while accepting that unlike disk, there is little or no hard data published for tape on “mean time to data loss”, or annual failure rates under various conditions. Given the high rates of dissatisfaction with tape based backup, vendor claims of long-term reliability may need to be reviewed with greater vigor.

Tape is only as good as its handlers

One of the major failings of tape, is not the technology itself, but the way in which it is treated. In many cases the staff entrusted with tape management and movement are in entry level IT positions, or semi skilled third party couriers. Even tape media manufacturers openly acknowledge that expected archival life times are only for tapes kept in “optimum” operating and storage conditions of 16C to 25C ,Relative Humidity 20% to 50%, and no shock or vibration, none of which apply to courier vans. In addition, tape drives must themselves be subject to rigorous preventative maintenance. The reason for this is that atape that is used in a drive that was not well maintained and has accumulated dirt and debris from dirty heads, roller guides and other transport assemblies, may find this debris gets transferred to the tape media. When these dirty tapes are subsequently used in a good drive, they may transfer some or all of those contaminants and degrade a previously clean drive. As the new drive becomes contaminated, a variety of problems can result, including premature head wear, debris accumulation on critical parts of the drive transport, and then damage to the tape. This leads to an even larger media impact as any new tapes that are used in the drive can also be damaged,

A further cautionary note when using a backup application for long-term archive is that the media is recorded in a proprietary logical format readable only by the originating application. Backup vendors have been known to discontinue backwards read compatibility for their own logical tape formats, and a change of backup vendors, or products from the same vendor may make recovery from archived tapes difficult, if not impossible to do. Thus, true long-term archive would also require archiving the entire backup system including the computer, recording hardware and software as well as multiple copies of the media.

While this post is really more about archiving than it is about backup, almost every backup environment I’ve ever come across is still used to store long term archives on tape media.  Most of the time this works reasonably well, but far too often it doesnt. To put this in perspective, if you needed the data on the tape to defend yourself in a legal battle, how would you feel about only having a “pretty good chance” of getting the informtaion you needed ?

Categories: Archive, Backup, Tape
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