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Triple parity Raid – WHY?

Wednesday, September 21st, 2016

Ever since the dawn of disk drives we have acknowledged and accepted that magnetic media is not infinitely stable and reliable and as such we have come up with many ways to protect the data we store on disk.

We have the basics of Raid 1 where we just mirror the data to another drive. This allows a drive to fail and we still have all the data, however this type of solution is expensive as we double the amount of storage required.

So moving forward we came to Raid 4, and 5. Both give a parity bit to enable the rebuild of any failed drive to a hot spare drive without the cost of replicating everything. This was later enhanced with Raid 6 and RaidDP, both of which allowed for two concurrent drive failures without the loss of access and those failed drives could be successfully rebuilt.

So why did we go from one parity to two. Well this is mainly due to the fact that we are using less space to store more and as such the drive mechanics are far more precise with very little tolerance compared to older style drives where the data was written to larger areas of disk and generically had higher tolerance.

We are now breaching new realms with the higher capacity drives they have some underlying quirks to them. Firstly, being larger capacity means typically that they take longer to rebuild when you have a failure, and this extended rebuild times extends your vulnerability to consecutive failures.

So we need better protection, especially when you consider that we are currently seeing a higher read error rate with SSD drives deployed throughout data centres.dsc_0124

So although today the thought process may hold you back from this additional level of protection, it will become more common practice to add another level of protection especially with the likes of the 15TB SSD drives. With rebuild times being around 12 hours for 15TB and with drive capacities continuing to grow it won’t be long before larger drives are available and in turn the rebuild for them will probably also extend in relation to the additional capacity.

Should you encounter a read error on a disk that is part of a Raid configuration then you are most probably never going to notice it as this error will be hidden or masked by having the parity checksum in a dual parity configuration, but to sustain operations when there are two read errors can only be done with a third parity bit. With that in mind especially with higher capacity and extended rebuild times it makes perfect sense to evolve and utilise the triple parity.

NetApp® have with OnTap 9 release RAID-TEC™ which serves two purposes. Firstly it gives the added parity protection in Raid with a Third parity bit, but also the reconstruction method has been redeveloped so that during a drive rebuild there is no performance degradation, this means you keep your performance and have a higher level of protection giving a higher level of confidence.

The new RAID-TEC™ (Triple Erasure Encoding) gives more usable space and better protection of large drive sizes. Another aspect of this that for any existing RAID-DP aggregates they will be able to convert to RAID-TEC non-disruptively, which is a major plus point in comparison to the older Raid4 and RAID-DP the drive counts are more conducive to storage efficiency.

 

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Pete Green
Fast Lane Lead NetApp Expert

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NetApp’s New OnTap 9 Features – introducing RAID-TEC

Tuesday, September 13th, 2016

With the release of OnTap 9, NetApp have introduced RAID-TEC, or triple erasure coding. With RAID-TEC, up to three spinning disks or SSDs can be lost without impacting capacity or crucially without affecting performance, Fore said. “With the latest large-capacity drives 15TB SSD drives, the rebuild times can be really long,” so a third drive protection gives better stability during the rebuild duration. Historically when a drive failed and was being rebuilt from data and Parity there was always an overhead on performance during the rebuild process. With RAID-TEC the performance is not affected during rebuild.

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Pete Green
NetApp Technical Instructor

 

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NetApp ONTAP 9 RC1 is now here!

Wednesday, September 7th, 2016

That’s right – the next major release of ONTAP is now available.

So, why do you need ONTAP 9?

Well if your version of ONTAP is working for you, great. No need to change a thing. But, once you see some of the feature enhancements in ONTAP 9, you might have a change of heart…..

Features aplenty!

The list includes:na_authorized-learning-partner_2c_rgb-(002)

  • Support for 15TB SSD
  • Inline data compaction
  • SnapLock® software for data compliance
  • RAID-TEC triple-parity protection
  • Headroom for visibility of performance capacity
  • MetroCluster enhancements (8 nodes!)
  • Onboard key manager (Included for FREE)
  • FlexGroups (PVR only in 9.0)
  • Workgroup mode for CIFS/SMB
  • LDAP Signing and Sealing for CIFS/SMB
  • Kerberos 5p support
  • AFF Simplicity templates
  • SAN Optimized factory configurations
  • Performance improvements
  • ONTAP Select (4 nodes, HA failover, software defined storage!)
  • Faster failover times
  • Per-aggregate CPs
  • Filehandle preservation for SVM DR – no more re-mounting after cutover!
  • Volume rehost
  • Global FIPS mode for FIPS compliance
  • TLS 1.1/1.2 support
  • Increased per-node LIF limits (cluster-wide limit remains)

That’s a lot of bang for your buck!

To view our upcoming NetApp training schedule follow this url – http://www.flane.co.uk/schedule/netapp

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