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 [...] ]]> 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.

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 [...] ]]> 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.

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.

http://www.thestoragearchitect.com/2009/09/08/review-western-digital-wd20eads-2tb-sata-ii-hard-drive/

THw WD20FYPS is a 2TB SATA drive from Western Digital’s Enterprise Drive range.  It boasts a larger cache and a whole range of features that should boost performance and reliability.  But are these benefits [...] ]]> This review covers the Western Digital RE4-GP drive, also known as the WD20FYPS 2TB SATA model.  Previous reviews:

http://www.thestoragearchitect.com/2009/09/08/review-western-digital-wd20eads-2tb-sata-ii-hard-drive/

THw WD20FYPS is a 2TB SATA drive from Western Digital’s Enterprise Drive range.  It boasts a larger cache and a whole range of features that should boost performance and reliability.  But are these benefits really worth the additional cost?

The Basics

The drive itself is a standard 3.5″ model and like its domestic equivalent the WD20EADS, weighs in at 730g.  It also has 4 platters and 8 heads, but offers an increased cache of 64MB and a constant speed of 7200RPM.  The four platters (or 8 surfaces) translate to a density of approximately 400Gb/in².  Here are the drive basics:

• Model Name: WD20FYPS
• Capacity: 2TB (2,000,398MB)
• Form Factor: 3.5″
• Platters: 4
• Areal Density: 400Gb/in²
• Interface: SATA 3Gb/s
• Rotational Speed: 7200RPM
• Max Sustained Throughput: 110MB/s
• Power (Typical): 6.8W
• Power (Idle): 3.7W
• Power (Standby): 0.8W

Advanced Features

The WD RE4 range sports a number of interesting features.  In fact every time a new drive comes out from one of the major manufacturers it seems to include new innovations.  On this range we have:

• Dual Actuator Technology – improves the accuracy of reads by using both mechanical and electronic positioning.
• Dual Processors – improved processing power.
• StableTrac – extra secure motor mountings to reduce vibration.
• RAFF (Rotary Acceleration Feed Forward) – reduces vibration issues in server & storage environments.
• Intelliseek – optimising of the seek speed to position the read head efficiently to reduce power and noise.
• RAID-TLER – Time limited error recovery to reduce the risk of soft RAID failures.

Clearly all these enhancements are intended to eke out more speed and performance from hard drives.  Let’s see how this one compares in the performance tests.

Performance Graphs

The first graph shows sequential write performance for the drive, which peaks at around 106MB/s.  Host cache settings have little effect and over the WD20FYPS model (which has less internal cache), performance is improved by around 7%.

As expected the drive performs well when caching is enabled, but throughput is extremely poor with totally random writes and no cache.

Summary

Double internal cache doesn’t provide much of an up-tick on performance and perhaps doesn’t justify the increased cost.  In fact, more performance would be gained using host-based caching or the use of a dedicated RAID or I/O card.

The next review will look at Seagate’s 2TB drive and compare performance to higher performance drives.

What happens to these hard drives? I presume they just end up in landfill and aren’t recycled. Is it beyond the [...] ]]> Many financial and government organisations choose to destroy the hard drives that are declared as failing and removed from their arrays. They use products like this which make the hard drive unusable.

What happens to these hard drives? I presume they just end up in landfill and aren’t recycled. Is it beyond the wit of man to find another solution?

First of all, a large number of these drives haven’t actually failed. They’ve been marked as having a potential to fail by the array and before a hard failure occurs, the data is moved off to a hot spare. Naturally it is more efficient to copy parity generated data like RAID-5/6 to another drive than to read all drives in the parity group and rebuild the data.

Second, we are imbedding encryption directly into the drive itself. Can’t we simply create a drive where the keys can be wiped in the event that the drive needs to be recycled? This seems to me to be the simplest and most elegant solution.

Incidentally, I checked the Hitachi Global Storage Technologies (HGST) website and could only see some nice words about caring about the environment but nothing specific relating to recycling itself.

However things aren’t that simple. Doing the comparisons and working out some of the basic [...] ]]> I was asked the question today, when will Enterprise arrays support 2.5″ drives as standard? It’s a good question, as at first glance the savings should be obvious; smaller, lower power drives, more drives in an array and so on.

However things aren’t that simple. Doing the comparisons and working out some of the basic calculations such as Watts per GB or GB per cm3 then 2.5″ drives don’t offer that much of a saving (if at all). I’ve posted some sample comparisons here.

I’m not aware of any vendors who are planning to offer 2.5″ drives in Enterprise arrays. Looking at the mechanics of making the conversion, then there would be a few issues; first is the interconnect, SAS versus FCAL, however that should be an easy one to resolve. Second, there’s the physical layout of the drives and prividing maintenance access to each of them. That might prove more tricky, achieving a high density footprint and providing access to each drive individually.

If anyone is aware of anyone planning to use 2.5″ drives as standard, please let me know.