Overview

Parallel writes is a configurable feature that affects the number of Web service requests that will operate in parallel across an instance of DryvIQ on a given node. It is important to note that increasing the number of parallel writes does not always equal faster or better transfer performance. A long list of concepts must be taken into account.

Parallel Writes and Memory Usage

A migration job in DryvIQ does not use a fixed amount of memory. Memory usage for individual jobs varies based on several factors, the most significant being the number of files and how those files are distributed (all in one folder, throughout sub-folders, etc.). DryvIQ recommends preserving the system default for Directory Item Limits to avoid excessive memory usage related to content distribution. The main factors for memory usage for a DryvIQ node will be the number of concurrent jobs, the number of parallel writes for the jobs, and the memory impact of the specific jobs.

If memory issues occur due to increasing the Directory Item Limit or parallel writes, there is no mitigation other than reducing the number of current jobs or breaking up the source content into multiple jobs. DryvIQ does not self-limit; it will keep using memory until it runs out and eventually reaches the environment’s max. Reaching an environment max may result in a non-graceful termination of DryvIQ that could result in jobs re-transferring files, permissions, or metadata. In the case of larger jobs being stopped in this manner, they will enter recovery mode, continue to use all the memory, then get stopped again, in a loop, causing a loss of throughput.

Default Parallel Writes

The default parallel write value is 4, 8, or 12, depending on the number of CPU logical processors on the machine running the DryvIQ service.

• If the CPU Logical Processors is 2, the default parallel writes value is 4.
• If the CPU Logical Processors is 8, the default parallel writes value is 8.
• If the CPU Logical Processors is 32, the default parallel writes value is 12.

Changing the Global Parallel Writes

The global parallel writes setting changes the settings for all jobs. If you want to change the setting for a single job, you must use the REST API to update the configuration for the individual job. Refer to Parallel Writes Per Job for more information on updating the parallel writes setting for an individual job. All nodes will be updated with the new setting if you have multiple nodes.

1. Click Settings in the left menu.
2. Select Performance.
3. In the Requested field, type the number of parallel writes you want to set.
4. Select Save.