Use this procedure to determine if you need a first write log device for your appliance. Fibre Channel and iSCSI writes are synchronous and benefit from log devices when the write cache is enabled. Be sure to thoroughly read and understand the documented implications of enabling write caching on LUNs before proceeding. For more information, see Space Management for Shares in Oracle ZFS Storage Appliance Administration Guide, Release OS8.8.0.
To determine if you need to add more than one write log device, see When to Add More Write Log Devices (CLI).
hostname:analytics worksheets> select worksheet-000 hostname:analytics worksheet-000> dataset
hostname:analytics worksheet-000 dataset (uncommitted)> set name=nfs2.ops[op] name = nfs2.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit
NFSv3 operations per second, broken down by type of operation (nfs3.ops[op])
NFSv4 operations per second, broken down by type of operation (nfs4.ops[op])
NFSv4.1 operations per second, broken down by type of operation (nfs4-1.ops[op])
iSCSI operations per second, broken down by type of operation (iscsi.ops[op])
Fibre Channel operations per second, broken down by type of operation (fc.ops[op])
SMB operations per second, broken down by type of operation (smb.ops[op])
hostname:analytics worksheet-000 dataset (uncommitted)> set name=nfs3.ops[op] name = nfs3.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name=nfs4.ops[op] name = nfs4.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name=nfs4-1.ops[op] name = nfs4-1.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name=iscsi.ops[op] name = iscsi.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name=fc.ops[op] name = fc.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name=smb.ops[op] name = smb.ops[op] hostname:analytics worksheet-000 dataset (uncommitted)> commit
hostname:analytics worksheet-000> done hostname:analytics worksheets> done
hostname:> analytics datasets
hostname:analytics datasets> show Datasets: DATASET STATE INCORE ONDISK NAME dataset-000 active 1.27M 15.5M arc.accesses[hit/miss] dataset-001 active 517K 9.21M arc.accesses[hit/miss=metadata hits][L2ARC eligibility] ... dataset-030 active 290K 7.80M nfs2.ops[op] hostname:analytics datasets>
In this example, dataset name nfs2.ops[op] corresponds to dataset-030.
hostname:analytics datasets> select dataset-030
hostname:analytics dataset-030> read 900
hostname:analytics dataset-030> done
NFSv3 operations per second, broken down by type of operation (nfs3.ops[op])
NFSv4 operations per second, broken down by type of operation (nfs4.ops[op])
NFSv4.1 operations per second, broken down by type of operation (nfs4-1.ops[op])
iSCSI operations per second, broken down by type of operation (iscsi.ops[op])
Fibre Channel operations per second, broken down by type of operation (fc.ops[op])
SMB operations per second, broken down by type of operation (smb.ops[op])
hostname:analytics datasets> show ... hostname:analytics datasets> select dataset-032 hostname:analytics dataset-032> read 900 ... hostname:analytics dataset-032> done hostname:analytics datasets> show ... hostname:analytics datasets> select dataset-034 ... hostname:analytics datasets> select dataset-27 ... hostname:analytics datasets> select dataset-13 ... hostname:analytics datasets> select dataset-07 ... hostname:analytics datasets> select dataset-40
You may want to add the first write log device when one or all of the following conditions are present:
The sum of iSCSI writes, Fibre Channel writes, and NFS/SMB synchronous operations is at least 1000 per second
There are at least 100 NFS commits per second