The Storage Architect » NAS

Hitachi Acquire BlueArc (At Last)

Chris M Evans — Thu, 08 Sep 2011 09:15:52 +0000

I don’t talk about company acquisitions too often but I can’t let the purchase of BlueArc by HDS pass me by without adding my opinion. First of all, for those of you who don’t know, BlueArc sells NAS hardware which has been resold by HDS for some years under the HNAS brand. The hardware comes stand-alone or can act as a gateway to HDS disk, such as the AMS series. Initially BlueArc positioned themselves at the high end of the NAS market, based on their dedicated FGPA processors, which offloaded some of the hard NAS processing work, but eventually moved to offering lower spec devices.

HDS/Hitachi I believe were an investor in BlueArc, now they’ve acquired them. I think this is a good move for both companies for a number of reasons. Firstly, it marks the continuing change in HDS’ strategy, which now includes acquiring companies, albeit companies that they have an existing relationship with. This approach may seem cautious but perhaps it’s a good thing to take time to understand the people, technology and culture, although HDS could have made their move earlier. Second, I believe BlueArc suffers in a market where (large enterprise) customers expect longevity. Committing to a new platform that suddenly has little or no development could be a costly mistake. There’s also the issue of global support and maintenance to consider too. Being part of Hitachi will give customers more reassurance.

Some time ago, I put the following diagram together as part of work for a customer. it was meant to show how the Hitachi technology can operate on a number of layers, from the physical hardware upwards. Although I have no specific inside knowledge, I expect Hitachi will converge the physical layer into a single device at some stage. Chris Mellor’s article hinted at this (although I expect this slide is no longer accurate) and developments in their technology imply this too. The AMS2XXX range certainly became more USP-like in its last release.

Operating a single hardware platform makes sense as HDS can abstract the hardware from the logical view using tools like HTSM and UVM. Presentation is then through native FC/FCoE or using gateway products to provide NAS and object connectivity. VSP represents a much more scalable architecture than the USP was, one of the key features being the abstraction of the front and back-end processors from the physical interfaces. This scalability easily supports multi-protocol shared environments.

Other vendors have gone down the route of doing scale-out through multiple interconnected nodes. I think this is a good approach and it could be argued that Hitachi have taken another way and gone for single monolithic arrays. I don’t believe this is the case as the VSP is already a cluster of two nodes and from the PCIe backplane architecture can presumably scale to more nodes as required. They are however more closely coupled than other implementations. If Hitachi delivers on the potential promise of HAM, then clustering/nodes can be implemented and the single monolithic array isn’t an issue. Now that Hitachi own BlueArc, they can integrate the functionality to ensure any NAS presentation can be mapped back to any storage array, with seamless migration.

So in summary, the future looks good, I’m looking forward to seeing how Hitachi capitalise on their new investment.

Disclaimer: I’ve been engaged with HDS as a blogger, including trips to Japan and the US. I have worked for HDS UK delivering consultancy to their clients.

Hardware Review: Promise SmartStor NS4600 – Part IV

Chris M Evans — Thu, 11 Nov 2010 16:58:14 +0000

This is a series of posts on the Promise SmartStor NS4600 home storage server. Previous posts:

One essential feature in any home NAS product is the ability to back up data. The NS4600 has three options for data protection; snapshots, NAS replication and a feature called Easy Backup.

Snapshots

The snapshot functionality is pretty much as you’d expect and can be found under the “Backup” menu option. Snapshot settings are set on a per-volume basis and unfortunately the maximum number for any one volume is four. This is somewhat limiting and could be pretty restrictive if the NS4600 was being used in a home/office environment where hourly backups would be more preferable.

Easy Backup

This feature enables data to be backed up to and from external devices across either the USB or eSATA interfaces. Data from the external device is backed up to a named folder on the NS4600. Backing up from the NS4600 can either be a full or synchronised copy. This can be useful when wanting to ensure a copy of data is available outside of the NS4600, in case the device malfunctions or worst case, is destroyed or stolen.

NAS Replication

Whilst the previous two features are useful, the one I could see more benefit from was NAS replication. This enables two NS4600 devices to replicate data between each other over the network. Setup of this feature is quite simple. One device acts as primary, the other as the secondary in a replication pair. There’s no ability to replicate in both directions at the same time as the feature is uni-directional. The screenshots show the setup of the replication feature and a replication task in progress. I had some trouble initially establishing replication as the documentation doesn’t make obvious what data is replicated. In fact it appears to be every file share in every volume and the target device needs to have an identical volume name structure to allow replication to work; so if the primary appliance as a VOLUME2, the target appliance must also have VOLUME2. Although replication is a useful feature, there are few shortcomings that should be addressed to make this a more usable. These would include:

More detailed log information on the success/failure of a replication task. If replication fails, the only way to get detailed information on the failure is to have enabled email alerts. The management log provides insufficient detail on the failure reason. Email support might not always be easy for users to implement as it requires SMTP server details.
More granular selection of the replication shares. I’d like to exclude some files from replication; for instance music files don’t need to be replicated necessarily, but accounts information does. Allowing at least share level replication would be a start.
I’d like to be able to specify source and target folders. NAS replication is simply using rsync, so it should be possible to achieve. I like to be able to clearly identify which directories are backups of primary data to prevent multiple update issues.
There doesn’t seem to be any way to stop replication once it has started. This could be a real issue if the replication task starts taking lots of network bandwidth and the only abort option is a reboot of the appliance.

Clearly Promise have realised that it’s essential to be able to secure data away from a single appliance. RAID and snapshots alone aren’t protection enough for device failure, theft or fire. Data copying also needs to be simple and no doubt in this regard the NS4600 replication is simple to establish. However this simplicity has also resulted in a lack of features, which needs to be addressed in future releases.

In the final article I’ll discuss some of the other features of the NS4600 and provide an overall summary of my thoughts.

Hardware Review: Promise SmartStor NS4600 – Part II

Chris M Evans — Thu, 01 Jul 2010 11:00:34 +0000

This is a series of posts on the Promise SmartStor NS4600 home storage server. Previous posts:

Hardware Review: Promise SmartStor NS4600 – Part I

In the first post of this series, we discussed the basic hardware configuration. This post will look at connectivity and RAID configurations supported by the NS4600.

A quick glance at the back of the unit provides a clue as to what connectivity exists. See the first image in this post. There is are 2x USB, 1x eSATA and 1x Ethernet ports available. The Gigabit Ethernet connection supports multiple host protocols, which we’ll discuss in more detail later. The eSATA port provides connectivity to external devices for either backup of the NS4600 or backup of the external device to the NS4600. The USB port also supports the same source and target backup functionality, meaning effectively all host connection protocols are IP-based. The USB port also functions as a printer server for USB printers.

RAID Support

The NS4600 supports RAID levels 0, 1, 5 & 10, implemented by the onboard Promise PDC42819 SATA RAID Controller. The required RAID level is specified at the time a volume is created; multiple logical volumes are supported on the NS4600 as long as there are sufficient disks available. This means, for example, two RAID-1 volumes could be created or a RAID-5 volume with another RAID-0 volume could be established. RAID settings are configured from the “RAID Management” option in the online GUI (PASM). A number of example screenshots showing various RAID configurations are displayed in the gallery at the end of this post.

Volumes form the foundation of how data is presented from the NS4600. They give the options to use RAID to manage the trade-off between capacity and performance. For example, a single RAID-0 volume could be used for backups, while the main data is RAID-1 protected, with a final drive kept as spare. Of course drives are hot-pluggable, so not all slots need to be initially populated. This means drives can be added to a RAID group to increase capacity over time. For instance two drives could be used to populate the NS4600 in the first instance. This can then be expanded dynamically, changing the RAID level or adding additional capacity.

Although RAID is implemented in hardware, the options available are reasonably flexible in offering multiple dynamically expandable configurations. However, I’d question whether traditional RAID implementations are the way forward in home storage devices. Bear in mind that 2TB drives are becoming the norm and that means within 18 months to 2 years, 3/4TB and even 5TB drives will become commonplace. As we move to much larger capacities, unrecoverable read errors become a real issue, so rather than recovering an entire disk, the ability to recover individual chunks of data is more preferable. This is the methodology Data Robotics have implemented within their BeyondRAID technology. Promise are playing the trade-off between rock-solid RAID-in-silicon versus RAID-in-software. At the moment my money goes with software RAID and the enhanced flexibility it brings.

RAID Rebuild on NS4600

Now I like a bit of fun with RAID systems and one of my favourite tricks is to exchange RAID drives within an array. So, on one of the NS4600′s, I powered it down, removed all the drives and powered it back up. Fortunately, the device configuration isn’t stored on the removed disks and the NS4600 remained accessible, although protesting at the fact no drives were present. After adding the drives back (in a random order) the NS4600 detected them and recovered the RAID sets and I was back in business. I wouldn’t advise removing all the drives in normal practice, however if a chassis completely fails, then presumably the data can be recovered in another unit (although I haven’t tested this).

Volumes

NS4600 - Free Disks - Unconfigured Volumes

Volumes are the logical entity that are created when establishing the RAID configuration of the NS4600. The screenshot below shows the NS4600 before any volumes have been created. There are four volumes in the free pool. The second screenshot shows two volumes that have been created from the four available drives in my test NS4600. Volumes and the RAID set on which they are stored are a 1:1 relationship; a volume may not span a RAID set and a RAID set may not contain more than one volume. This may seem a little restrictive, however as we’ll see later, file systems and iSCSI LUNs are

NS4600 Multiple Volumes

contained within a volume and therefore volumes should be thought of as providing specific RAID availability.

Volumes can be expanded; see the screenshot, which shows a volume in the process of being expanded. This volume is being converted from RAID-1 to RAID-5. RAID-0 volumes can be expanded to larger RAID-0 volumes or moved to RAID-1 or RAID-5 configurations. Basically, volumes can be increased in size or moved to a higher level of RAID protection – but not down.

NS4600 Disk Formatting

The NS4600 has the concept of spares as opposed to free (unused) disks. A hot spare can be used to dynamically rebuild a failed RAID group. The screenshot shows a rebuild in place for a failed drive. In this instance I’d left drive 4 as the hot spare and pulled drive 1 to simulate a failure. The NS4600 automatically kicks off the rebuild and spare drive becomes part of the RAID group. Now we see the second issue with the use of traditional RAID systems. I simulated this RAID failure on RAID groups containing no data, yet the rebuild took hours due to the nature of the rebuild – a physical

NS4600 Raid Rebuild

drive recovery. Contrast this with more progressive RAID systems where only the active data is copied, significantly reducing recovery times. Of course the trade-off here is whether in a home system you would be rebuilding on a regular basis. Chances are you wouldn’t but if a failure did occur, you would want it to occur as quickly as possible. For the record, the total rebuild of a 2TB drive in a mirrored RAID-1 pair took 12 hours to complete with no other workload on the device.

In the next post I’ll look at the logical level of file systems and iSCSI LUNs. Comments always welcome as usual.

Disclaimer: Promise have provided me with two NS4600 devices for this review. These devices will be returned at the end of this period. This is an independent review and has not been sponsored or paid for by Promise.

Hardware Review: Promise SmartStor NS4600 – Part I

Chris M Evans — Fri, 25 Jun 2010 16:04:17 +0000

This is a series of posts on the Promise SmartStor NS4600 home storage server.

Background

Promise Technology Inc have been manufacturing RAID controllers since 1988 and iSCSI storage systems since 2004. In 2007, the company released the first of the SmartStor devices, the NS4300, a fully-functioned home NAS storage array. That was followed up in 2009 with the second generation NS4600. I must admit I’m not at all familiar with their products, however Promise have provided me two NS4600 units for a short term evaluation. The home NAS server market has become pretty competitive, with lots of features built into todays’ hardware. What made the NS4600 interesting is the ability to backup between devices; something we will cover in these posts. The ability to replicate to another unit will make it compelling for those advanced users who have large volumes of data to secure.

The NSx600 range are classed as high performance SOHO or home NAS devices and have the following specifications:

Processor: Intel EP80579 600Mhz
Memory: 256MB DDRII
1x GbE port
1x eSATA port
2x USB ports
Four 3.5″ SATA drive slots
Promise PDC42819 SATA RAID Controller

The device itself is pretty solid despite feeling quite light without the drives installed. In terms of design, the unit looks quite attractive, with blue LEDs on the front, showing drive and network activity. Drives are installed behind a single door in a horizontal fashion and are required to be mounted in small caddies. These are screwed to the drive itself and aren’t large and provide the runners for correct insertion. Drives are hot-pluggable while the unit is running.

At the rear of the unit, there are the network connections and power socket for the integrated power supply. There’s also a power button for turning the unit on and off. For cooling, there’s an integrated fan;

this kicks out a reasonable amount of heat when all four drive slots are occupied. Although we’ll touch on software and management later, it’s worth mentioning here that the device (or enclosure as it is described) can be monitored through the built-in web server interface. Screen shots are included at the end of this post and show the power, fan and temperature metrics being tracked. I like this feature; it provides that extra level of information needed when doing problem determination.

Overall, the the NS4600 hardware is pretty cool. In future posts, we’ll discuss software features and management.

Cloud Computing: Cloud /= Virtualisation

Chris M Evans — Mon, 15 Mar 2010 13:04:13 +0000

I finally managed to attend a London CloudCamp last Thursday, which conveniently co-incided with a #storagebeers evening. For two hours of listening to the collective wisdom of the presenters and the “unpanel” we were offered free beer and food. Now free beer is good, however I’m not sure it’s good enough to make me want to listen to yet another presenter confuse Cloud with Virtualisation. This may have been a genuine misunderstanding, however it may also have been quite deliberate, as the speaker in question works for a VMware partner. However moving on, here’s what I think Cloud is, should be and will be.

My Cloud View

Cloud is not virtualisation. Virtualisation is virtualisation. It’s a way of consolidating the physical entities we know today and making them available in the same manner in a virtualised form. Moving 1000 Windows servers to 1000 virtual machines changes nothing. You’re still offering IT to customers in the same way – using the concept of that physical entity called a server. This is a step forward in reducing cost, but not in delivering cloud.

Cloud today is a hybrid of two things; virtualisation & services and service abstraction. In the first form, Amazon, Rackspace and the others are offering the same physical objects (i.e. servers) but packaged nicely so they can charge you efficiently for them. What makes this kind of environment a step above virtualisation is that you have no view, concern or interest in how, where or by whom those servers are being provided as long as they meet your requirements for security and availability. The hosting company is effectively offering you elasticity over and above the basic virtualisation offering you could achieve yourself. If you need more compute, then they guarantee to provide it and they manage the pain of ensuring resources are available. Second, is service abstraction; some things are non-server dependent. For instance; generic databases or email outsourcing. The hosting company offers you a service, rather than a virtual device. This leads on to the next step; what Cloud will be in the future.

To see what Cloud Computing can offer, we need to move forward away from the fixed view of infrastructure and start thinking about data and applications. In the future I want to move away from thinking about fixed data types like files and block devices and think about objects and metadata. These objects need to be modifiable in a way that gives me consistency, so if I lose a node, or device that’s processing the data, I can recover it from elsewhere and continue working. I want to process my data in parallel and without geographic constraints, so I can run or move my workload anywhere; presumably to the provider who is offering me best price on that day.

The treatment of data in this form means I need to rethink how applications are written. I can’t rely on a simple client-server hierarchical architecture but need to move to one where my processing and data is distributed.

Re-writing distributed applications will be the hardest part of delivering Cloud Computing.

Application development in a completely distributed environment creates significant challenges. Here are a few of the most obvious issues;

How do I ensure consistency (multiple updates in multiple locations)?
How can I manage performance?
How can I move my data around easily and quickly?
How can I back my data up?
How can I move my application and/or data to make best use of cost savings?
How can I ensure my data remains secure?

The ultimate Cloud Computing model needs to remove almost all the aspects of infrastructure structure we know today (server types, storage arrays, block devices, NAS) from the customer. It will offer abstracted programming concepts – store, retrieve, search, update – to process data. Customers will be charged for their consumption of these resources. Abstraction will allow applications to be run on (almost) any environment. These services will still be delivered on infrastructure, but we won’t care or need to care what it looks like. Now there’s a challenge…

Virtualisation: Virtualising MY SOHO Infrastructure

Chris M Evans — Wed, 02 Dec 2009 12:48:29 +0000

I’m in the process of migrating my existing physical infrastructure into a virtual environment. There’s nothing like “eating your own dog food” (there’s got to be a better expression than that) for testing out your beliefs on how technology should be implemented, so it’s only fitting I virtualise the IT infrastructure I rely on.

In summary, I run a “production” Windows AD domain, Exchange, IIS and file services. This is a typical scenario for many small businesses, with perhaps a few variations thrown in for good measure, such as SharePoint. I’m moving to a virtual environment that is built on ESXi v4.0, a custom design Intel-based server with 2x Quad Core Intel 5420 processors and 16GB of memory. Local hard drives include 2x SAS 7.2K 500GB drives and 2x 73GB SAS 15K drives.

Storage Choices

The first question I posed for my infrastructure is to decide on a storage platform. As this is a SOHO type deployment, I don’t have the luxury of a fibre channel SAN environment. I expect that many SMBs will feel the same and not want to commit to fibre channel deployments when the alternative options out there are low cost and probably more suitable. Therefore here are my choices:

Internal drives. I have over a terabyte of internal storage but unfortunately its not RAID protected. The disks are deployed on SAS connectors on the motherboard rather than through a dedicated RAID card. Although I could change the configuration and include a card, there are a number of issues; (a) increased cost (b) downtime to replace failed drives (c) physical intervention and downtime on the server to replace drives. My goal is to deploy this infrastructure to run 24×7, so having to take the system down to replace a drive is not an option. I also think that internal drives wouldn’t give me the scalability I might need.
iSCSI. In this environment, iSCSI is a great solution; there are lots of SMB iSCSI solutions on the marketplace today, offering low cost storage with simple operations. iSCSI is definitely a possibility.
NAS. Using NAS (more specifically NFS) for storage on VMware provides lots of flexibility. The management of the filesystem itself moves to the NAS hardware and so any VMware host files appear as standard files on the NAS device. When people see this, they usually get the “light bulb moment” as they realise the possibilities this kind of deployment offers. Whole virtual machines can be cloned, backed up or even simply copied as files around the infrastructure. NAS offers easy access to log and configuration files too.

So, for me the choice is NAS. I have iSCSI deployed, but for my production environments, NAS will be used to store my VMware hosts. This is for a variety of reasons, however there’s one additional benefit I haven’t discussed and that’s portability. Placing my vmdk’s on NAS means I can move them around at will. I can replicate them, I can back them up and I can move them easily to another NAS device without using ESXi as the data mover.

Stay tuned for more discussions as I evolve my setup.

Enterprise Computing: Symantec FileStore

Chris M Evans — Mon, 05 Oct 2009 08:32:22 +0000

Today Symantec are announcing their scalable NAS product called FileStore. This simple appliance claims to offer linear scaling for up to 2PB of storage per cluster, leveraging all the benefits of the Veritas storage products we’ve come to know and love over the years. But what chance has this competitor in a crowded market?

Have a look a the graphic on the right. This pretty much sums up what FileStore is about – it’s an appliance serving standard file system protocols (NFS/CIFS/FTP/HTTP) using whatever storage you choose to place at the back end. Up to 16 ‘nodes’ can be clustered together, working as a single load-balanced entity. Each node uses commodity x86 hardware.

OK, so these features offer nothing special so far. However, Symantec are using their Veritas heritage to provide some useful functionality into the product. Firstly, nodes can be added and removed transparently, including the addition of nodes at higher specifications and O/S levels. This means the technology can easily be refreshed over time; a painful scenario that most storage admins don’t like to have to go through. Replacing storage is also simple as FileStore uses the Veritas File System under the covers. Think of how a ‘plex’ can be replaced on a VFS today – add a new plex from the new storage, mirror these up and remove the old plex – voila!, transparent migration.

There’s also the option of tiering storage at the file level, another benefit of using VFS. Individual files can be mapped to tiers of storage based on customer-defined policies, which provides the exact level of granularity needed.

What about scale? Well, Symantec claim linear scalability and a SPEC SFS rating that will exceed the ones posted by Netapp. These figures aren’t available yet but when they are will make interesting reading. Finally there’s the thorny subject of the existing customer base. Symantec claim to have been using FileStore to support their SaaS online backup service for the last 3 years. This stores around 40PB of data for 9 million users. In addition, there are large customers around the world already using FileStore, including TaoBao in China.

OK, it can’t all be good news. What marketing slides tend not to show are the little details that matter, such as management interfaces and feature sets. I’ve not seen details on what other functionality is available with FileStore - snapshots, replication, de-duplication, compression, encryption all come to mind. However with a starting price of $6995 for a 2-node 2-socket system, do many of those features matter?

Drobo Update

Chris M Evans — Tue, 15 Apr 2008 18:09:00 +0000

I’ve had my Drobo for a few months now. For those of you not familiar with the technology, the Drobo is a storage device from a company called Data Robotics. Follow the link above to their website for full details.

I’d been looking for a decent home/home office storage device for some time. RAID support was a must and initially I thought I wanted NAS because my solution at the time was to keep a server running continuously. The server performs other tasks and I was using it for file serving too.

Previously I had taken the plunge with the Linksys NSLU2 which runs a modified version of Linux. Unfortunately at the time, the device only supported ext3 filesystems and as I loaded the device with more data, responses became erratic and I found the exported systems going read-only and losing content. Lucky for me the problem seemed to be the device rather than the actual data on disk and I was able to recover everything using a little software utility which allowed me to read ext3 devices on Windows. This experience scared me and it was time to look for something else.

The Drobo hit the spot for a number of reasons; firstly it was a dedicated device which took SATA II drives. It has a USB connection, allowing me to plug it directly into my existing server and third (and at the time most importantly) Data Robotics had just released a NAS head which could be used with the standard Drobo, or removed without affecting the format of data on the device itself.

So, as I said, I’ve had it for a few months and what is there to say about it? Well, not a lot. It works – and so far has worked flawlessly. But there are a few things of note.

Firstly, I have a BIOS incompatibility issue; when my server reboots, if the Drobo is plugged into a USB port, it hangs the server. I haven’t bothered to resolve this yet; weighing up the relative merits of just living with this problem or upgrading the BIOS on my server, then I fall squarely on the side of accepting the workaround of unplugging the drive at boot time and plugging it back in as the system comes up. If I was using a standalone PC, then I would obviously have fixed the problem.

Second, I was interested to see that despite my system having two 1TB drives and RAID protection, the X: drive I’d created reported back a 2TB file system. Was RAID on or not? Well, yes it was; the Drobo presents a 2TB file system regardless of the drives you have installed. It’s virtualisation in action! As you allocate all of the physical storage available, you get prompted to add or swap drives to match the physical demand. I like this feature as it’s a painless way to upgrade your storage over time and as terabyte drives drop in price (currently I’ve seen them at 1TB for £99) it helps smooth out the cost of upgrade because drive sizes can be mixed and matched.

Last, there’s the issue of firmware upgrade. Version 1.1.1 of firmware is available and it was a simple task to upgrade, however I can’t implement the code without rebooting the Drobo and that requires closing all the active files accessing the Drobo on the server. This is not a major problem though and wouldn’t be a problem on a standalone PC.

All in all, the Drobo looks good and does the job. Having 1TB of new capacity has encouraged me to spend time moving my data over in a controlled and structured fashion. The process will take months (a subject I will return to), but in the meantime I have bags of spare capacity and an easy upgrade path for both additional capacity and NAS connectivity.

Now, if anyone out there would like me to review their NAS product, then I’d be only too happy….

Storage as a commodity

Chris M Evans — Tue, 17 Apr 2007 21:41:00 +0000

I just read a comment over at Zerowait regarding Netapp and proprietary hardware. It reminded me of something I was thinking about recently on the commoditisation of storage.

There’s nothing worse to my mind than a storage vendor who has no competition. Inevitably in some organisations that situation can exist when a single supplier is chosen to supply (for example) switches, SAN or NAS. The difficulty though is how to avoid that situation. Most vendors would love to lock you into their proprietary tools and relating back to the above article link, Netapp is one I see who try that more than anyone. They have a bewildering array of interlinked product options; once your hooked (especially where you use a feature to retain long term backups via snapshot/vaults) then you’re sucked into a dependency on their products which just isn’t healthy.

What’s the solution? Well, for me I like to commoditise storage functionality. Pick out those features which all vendors support and only use the proprietary features where absolutely necessary. At least then you can maintain multiple vendors all on the hook for your next piece of business.

Of course implementing commoditised storage is more difficult than just picking a few common product features. However as far as your users are concerned, a LUN is a LUN and NAS storage is NAS storage, with a few caveats on things like driver levels for HBAs and so on.

I’ve previously posted a modular storage comparison sheet. As an example, here are some of the features that almost all support:

RAID 5 protection
Consistent LUN size
dual pathing
Active/Passive failover
remote replication
Fibre Channel presentation
SNMP alerting
online code upgrades
hot swappable components

Before I get lots of comments saying “hold on, not all modular products are the same”; remember I’m not saying that. What I am saying is having a consistent set of requirements allows you to maintain a shortlist of vendors who can all enjoy the healthy competition of bidding for business. So, time to draw up a NAS spreadsheet….