This was a panel like session that wasn’t vendor specific but broadly gave pointers on new type of arrays – like all vSAN,SDRS, VVOLs, flash arrays, datastore types, and jumbo frame usage etc. It truly lived up to its name – not just by content but also by its duration. The session ran over its scheduled duration of 1 hour and actually finished in 1.5 hours but no one was complaining since there was a lot of interesting stuff.
Presenters – Rawlinson Rivera (VMware), Chad Sakac (EMC), Vaughn Stewart (Pure Storage)
The session kicked off by talking about enabling simplicity in the storage environment. Some key points discussed were –
1) Use large datastores
- NFS16Tb and VMFS 64Tb
- Backup and restore times and objectives should be considered
2) Limit use of RDMs to when required for application support
3) Use datastore clusters and SDRS
- Match Service Levels on all datastores on each datastore cluster
- Disable SDRS IO Metric on all flash arrays and arrays with storage tiering
4) Use automated storage array services
- Auto tiering for performance
- Auto grow/extend for datastores
5) Avoid Jumbo frames for iSCSI and NFS
- Jumbo frames provide performance gains with increased complexity and the improvement in storage technology no longer requires Jumbo frames
They spoke about the forms of Hybrid Storage and categorized them based on their key functionality –
- Hybrid arrays – Nimble, Tintri, All modern arrays
- Host Caches – PernixData, vFRC, SanDisk
- Converged Infrastructure – Nutanix, vSAN, Simplivity
Benchmark Principles
Good Benchmarking is NOT easyYou need to benchmark over time – most arrays have some degree of behaviour variability over time
- You need to look at lots of hosts, VMs – not a ‘single guest’ or ‘single datastore’
- You need to benchmark mixed loads – in practice, all forms of IO will be flinging at the persistence layer
- If you use good tools like SLDB or IOmeter – recognize that they are still artificial workloads, and make sure to configure them to drive out a lot of different workloads
- With modern systems (particularly AFA’s or all flash hyper-converged), its really, REALLY hard to drive sufficient load to saturate the system. Have a lot of workload generators (generating more than 20K IOPS out of a host isn’t easy)
- Absolute performance more often than not is not the only design consideration
Storage Networking Guidance
VMFS and NFS provide similar performance
- FC, FCoE and NFS tend to provide slightly better performance than iSCSI
Always separate guest VM traffic from storage and VMkernel network
- Converged infrastructures require similar separation as data is written to 1+ remote nodes
Recommendation: avoid Jumbo frames as risk via human error outweighs any gain
- Goal is to increase IO while reducing host CPU
- Ethernet is 1500 MTU
- Jumbo frames are often viewed as 9000 MTU (9216)
- FCoE auto negotiates to ‘baby/ – jumbo frame of 2112 MTU (2158)
- Jumbo frames provide modes benefits in mixed workload clouds
- TOE adapters can produce issues uncommon in software stacks
Jumbo Frame summary – Is it worth it ?
Large environments may derive the most benefit from Jumbo frames but are also the most difficult to maintain compliance
– All the steps need to align – on every device
Mismatched settings can severely hinder performance
– A simple human error will result in significant storage issue for a large environment
Isolate jumbo frames iSCSI traffic (e.g. backup/replication) – apply CoS/QoS
Unless you have control over all host/network/storage settings, best practice is to use standard 1500 MTU
The future – Path Maximum Transmission Unit Discovery (PMTUD) – It is an IP packet (L3 routers) whereas Jumbo frames are L2 (switches)
It is part of ICMP protocol (same protocol that has Ping, Traceroute, etc) and is available on all modern Operating Systems.
The speakers then got into Data Reduction technologies – they are the new norm (specially de-duplication in arrays)
Deduplication is generally good at reducing VM Binaries (OS and application files). Deduplication block size variances can be impacted by GOS file system fragmentation
- 512B – Pure Storage
- 4KB – NetApp FAS
- 4KB – XtremIO
- 16KB – HP 3Par
- Performance
- Resynchronization
- Rebuilding Operations
- Pass-through node preferred
- Don’t mix disk types in a cluster for predictable performance
- More disk groups are better than one
The session finally concluded at 6:30pm and after a few hand shakes everyone was on their way. But it was completely worthwhile and goes on to show why attending VMworld offers great insights that you cannot learn in a 4 day course. The structure and content of these sessions is not limited by any way.