VMworld 2017: Storage at memory speed

Session: FUT3040BU, Richard Brunner

Speed analysis is dependent on storage and database access latency. A key component is local storage latency – nothing can compete with DRAM

What if you can move storage closer to the processing? You can with byte-addressable persistent memory (PMEM)

Future vSphere will bring PMEM support using virtualized NVDIMM device

What is PMEM? Few hundred nanoseconds latency; byte-level access; regular non-privileged access; load/store CPU instructions

Updating storage at a finer grain level – read/modify/write latency is vastly less than block-storage

Uses: fast-caching layer; database logs; etc.

With future vSphere release – no VM driver needed. Guest storage is directly mapped to PMEM transparently.

PMEM is vMotion and FT compatible

DIMM size can range from 8 GiB to 100s of GiB

PMEM Tech: 3D XPoint; HPE DIMMs; HybriDIMM

All PMEM solutions need a way of ensuring that the last set of updates have ‘made it’ to the persistent media

Server hardware, firmware, and software support

VMware Implementation of PMEM

Concept: Virtualize and manage NVDIMMs; accelerate legacy legacy and modified applications; virtual disks stored on PMEM; Byte addressable virtual hardware

Two access methods: vSCSI with VMDK; vNVDIMM with modern OS (WS2016)

FT will be compatible with vNVDIMM for high availability

vCenter & DRS will support PMEM and manage it at a cluster level

Maintenance mode can also vacate powered off hosts too and move their data

New VM creation workflow will have a PMEM storage option

Add new device will now have a NVDIMM option – up to 64 per VM

Storage migration will also support NVDIMM

Modes of operation:

NVMe SSD – Requires emulation and multiple layers to access device – slowest mode

vPMEMDISK – No storage stack needed and faster performance

nNVDIMM Рonly Filesystem  needed Рvery fast

vNVDIMM DAX – (Direct access mode) directly maps blocks into the application (fastest)

DAX mode Р35GB of persistent  data written in a second (512KB random writes)

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