Feeds

Dell internalises EqualLogic's automated data movement

Better than Compellent, it claims

7 Elements of Radically Simple OS Migration

Comment Dell contacted us when we reported on its 10GbitE product announcements to say that contrary to our first impression, that it did have "auto-data movement between tiers of EqualLogic storage."

How does this work when EqualLogic arrays have to have homogeneous disk drives inside them?

Compellent has had automated data movement between different performance tiers of storage in its arrays for some time. EMC is adding it, under the FAST moniker, to its arrays. 3PAR is also making moves in that direction, as is Symantec. The general trend to add solid state drives (SSDs) to storage arrays is encouraging vendors to automate the movement of data to and from SSD storage, as its access profile waxes and wanes.

Dell's EqualLogic arrays support different tiers of storage. An EqualLogic array consists of a pair of drive controllers linked to drive enclosures. Such an array is a unit and a unit must use the same disk drives.

A number of arrays can be combined into a group and present a virtualised pool of storage. The arrays in that group can have different tiers of storage, faster or slower drives for example. A customer can set up RAID groups, logical groups of drives sharing a RAID protection scheme, within such a group. The drives within a RAID group must be homogeneous, though.

Different RAID levels have different biases towards performance and protection/availability and capacity. RAID-10 stripes data across the disks in the group on top of RAID 1 (mirrored) sets, providing the highest availability and random write performance but lowest capacity. RAID-5 (distributed parity) has lower availability and random write performance. RAID-50 stripes on top of RAID 5 sets and provides better performance.

Eric Schott, Dell's director of product management, says: "RAID types have a very large impact on performance. A 10K drive running RAID-50 could be slower than a [7200rpm] SATA one running RAID-10."

Separate SAN (storage area network) pools can also be set up across EqualLogic arrays, so that, for example, data from different customer departments is logically separated. Different pools can have different tiers of disk storage - 15K SAS drives or 7,200rpm SATA drives for example - so that apps with different SAN I/O requirements can be allocated to the right pool. Customers can manually move data between pools, but not do it automatically. Schott says such manual moves do not disrupt data access by connected application servers.

EqualLogic arrays carry out load-balancing to optimise performance and Schott says: "We only load balance within a pool," so that I/O burdens into a pool are shared equally across all the array controllers with drives in that pool. After a new volume is first created, it has a performance history accumulated for it. The EqualLogic system may then move the volume within the pool RAID group so as to optimise its performance.

It is not moved from one drive type to another, though. There would be no such automated movement from a SATA drive-based pool to a faster SAS drive-based pool and mixed-drive type pools are not allowed.

Schott said: "We are absolutely not looking at the disk type level, SAS or SATA."

Dell competitor Compellent has automated data movement at the block level, which is not something that Dell's EqualLogic arrays do. But Dell asserts that it does not matter from a performance point of view, with Schott saying: "We don't lose in my experience to Compellent based on performance. We do much better than them on overall performance per drive. Candidly, I haven't run into them beating us or even being close to us [on performance]."

Our understanding is that an EqualLogic development may be coming in 2010 which could involve EqualLogic controllers having several storage tiers below them. Whether it would also involve automated data movement between storage tiers remains to be seen. ®

Best practices for enterprise data

More from The Register

next story
Microsoft's Euro cloud darkens: US FEDS can dig into foreign servers
They're not emails, they're business records, says court
Sysadmin Day 2014: Quick, there's still time to get the beers in
He walked over the broken glass, killed the thugs... and er... reconnected the cables*
VMware builds product executables on 50 Mac Minis
And goes to the Genius Bar for support
Multipath TCP speeds up the internet so much that security breaks
Black Hat research says proposed protocol will bork network probes, flummox firewalls
Auntie remains MYSTIFIED by that weekend BBC iPlayer and website outage
Still doing 'forensics' on the caching layer – Beeb digi wonk
Microsoft says 'weird things' can happen during Windows Server 2003 migrations
Fix coming for bug that makes Kerberos croak when you run two domain controllers
Cisco says network virtualisation won't pay off everywhere
Another sign of strain in the Borg/VMware relationship?
prev story

Whitepapers

7 Elements of Radically Simple OS Migration
Avoid the typical headaches of OS migration during your next project by learning about 7 elements of radically simple OS migration.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Solving today's distributed Big Data backup challenges
Enable IT efficiency and allow a firm to access and reuse corporate information for competitive advantage, ultimately changing business outcomes.
A new approach to endpoint data protection
What is the best way to ensure comprehensive visibility, management, and control of information on both company-owned and employee-owned devices?