Ultra Disks are the highest performance tier of Azure managed disks for data-intensive workloads. They deliver high throughput and IOPS, and consistent low latency disk storage. Customers can dynamically change the performance of the disks without the need to restart your virtual machines (VM).
For HPC/AI workloads, the Ultra Disks can be used as a higher performance tier to Premium Disks for remote storage scenarios (NFS pools, parallel file systems, etc.)
Considerations for Ultra Disks vis-a-vis Premium Disks
Note that the availability of Ultra Disks by region/AZ/SKU is different (and restrictive today) from that of Premium Disks. Even though a VM size is supported, the support is different per region/zone.
HPC and GPU VM SKUs with Ultra Disks
The table below demonstrated averaged bandwidth, IOPS and latency numbers on some of the HPC and GPU SKUs. These are obtained obtained using fio.
|VM SKU||Premium (20000 GB)||Ultra (1024 GB)|
|Spec: BW 900 MBps, 20K IOPS||Spec: BW 2000 MBps, 80K IOPS (single VM)|
|BW (MBps)||IOPS (K)||Latency (ms)||BW (MBps)||IOPS (K)||Latency (ms)|
|HC44||876 (R, W)||20||2.495||700 (R), 1944 (W)||64||0.215|
|HB120_v2||876 (R, W)||18||2.422||840 (R), 1946 (W)||30||0.235|
|NV48_v3||880 (R, W)||20||1.51||1172 (R, W)||80||0.339|
|NV32_v4||703 (R, W)||20||2.258||703 (R, W)||49||0.242|
|NDv2||876 (R, W)||20||2.207||710 (R), 1173 (W)||78||0.216|
|NC64_T4_v3||704 (R, W)||20||2.149||704 (R, W)||49||0.254|
Impact of Accelerated Networking
None. AccelNet does not improve Managed Disks performance. Exceptions maybe corner cases of the VMs doing heavy VM-VM network traffic over the Ethernet interface while doing VM-Managed Disk traffic at the same time.
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