Task #15539
open
Update Keep Filesystem driver doc to discourage Serialize: True
Description
We should even more strongly discourage the use of Serialize: True since it will almost always cause lower performance given request reordering in both the drive and operating system.
https://doc.arvados.org/install/configure-fs-storage.html
https://en.wikipedia.org/wiki/Tagged_Command_Queuing
https://en.wikipedia.org/wiki/Native_Command_Queuing
https://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface
Current text:
# When true, read and write operations (for whole 64MiB blocks) on # an individual volume will queued and issued serially. When # false, read and write operations will be issued concurrently. # # May improve throughput if you experience contention when there are # multiple requests to the same volume. # # When using SSDs, RAID, or a parallel network filesystem, you probably # don't want this. Serialize: false
Updated by Tom Morris
Updated by Ward Vandewege over 4 years ago
The use case this is intended for - and where it provides optimal performance - is a bare metal scenario, where there is no raid controller (or possibly a raid controller that is configured in JBOD fashion), the disks are spinning rust and exposed individually to the operating system, one per mounted volume.
In this configuration, enabling serialization of requests minimizes disk seeks, and it leads to improved performance under heavy load.