WARNING A single process is both a transaction log and a storage server

WARNING: A single process is both a transaction log and a storage server.
For best performance use dedicated disks for the transaction logs by setting process classes.

We have this warning and have some question

we have
1 ssd for 2~3 process

what we must change

use 1 ssd for all process log
and other ssd for data

[fdbserver.4500]
datadir = /ssd1/data/foundationdb/data/$ID
logdir = /ssdLOG/log/foundationdb
[fdbserver.4501]
datadir = /ssd2/data/foundationdb/data/$ID
logdir = /ssdLOG/log/foundationdb

or
change for process data in one ssd and log other ssd for all process

[fdbserver.4500]
datadir = /ssd1/data/foundationdb/data/$ID
logdir = /ssd2/log/foundationdb
[fdbserver.4501]
datadir = /ssd2/data/foundationdb/data/$ID
logdir = /ssd3/log/foundationdb

now we use

[fdbserver.4500]
datadir = /ssd1/data/foundationdb/data/$ID
logdir = /ssd1/log/foundationdb
[fdbserver.4501]
datadir = /ssd2/data/foundationdb/data/$ID
logdir = /ssd2/log/foundationdb

Configuration:
Redundancy mode - triple
Storage engine - ssd-2
Coordinators - 5

Cluster:
FoundationDB processes - 300
Machines - 10
Memory availability - 8.5 GB per process on machine with least available
Retransmissions rate - 2 Hz
Fault Tolerance - 2 machines
Server time - 07/18/19 17:31:54

Data:
Replication health - Healthy
Moving data - 0.000 GB
Sum of key-value sizes - 692 MB
Disk space used - 35.854 GB

Operating space:
Storage server - 1696.9 GB free on most full server
Log server - 1696.9 GB free on most full server

Workload:
Read rate - 51 Hz
Write rate - 0 Hz
Transactions started - 12 Hz
Transactions committed - 0 Hz
Conflict rate - 0 Hz

Backup and DR:
Running backups - 0
Running DRs - 0

Client time: 07/18/19 17:31:35

WARNING: A single process is both a transaction log and a storage server.
For best performance use dedicated disks for the transaction logs by setting process classes.

https://apple.github.io/foundationdb/configuration.html#guidelines-for-setting-process-class is the official documentation on this subject, but there’s also been a number of threads over time. For example:



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