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Linux Recommended Settings for NGX Storage

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This guide provides best practices to ensure optimal performance form Linux host environments with NGX Storage. In this example, we used Red Hat Enterprise Linux 8, but this procedure also works on Pardus, Ubuntu, Debian, openSUSE , SLES, Rocky Linux systems. 

IO Schedulers and Queue Settings

The disk scheduler is responsible for ordering the I/O requests submitted to a storage device.  NGX Storage recommend to change the I/O scheduler to “none” (for RedHat 7 it is “noop“),  to get better performance with lower CPU overhead than the default schedulers.

This settings can be change per device on a running system (at runtime, lost once rebooted).

Collect NGX-IO devices:

# grep NGX-IO /sys/block/sd*/device/vendor 
/sys/block/sdb/device/vendor:NGX-IO   
/sys/block/sdc/device/vendor:NGX-IO   
/sys/block/sdd/device/vendor:NGX-IO   
/sys/block/sde/device/vendor:NGX-IO

Turn on the none scheduler for a device:

$ echo 'none' > /sys/block/sdb/queue/scheduler
$ cat /sys/block/sdb/queue/scheduler
[none] mq-deadline kyber bfq

You can use below example to quickly set all NGX luns to the ‘none’ elevator:

# for sd in $(lsscsi | grep NGX-IO | awk '{print $7}'); do 
   echo none >  /sys/block/${sd##/dev/}/queue/scheduler ; 
  done

These changes will not persist unless they are added with TuneD or the udev rule for Linux hosts.

Setting the Disk Scheduler Using TuneD

Below procedure creates and enables a TuneD profile that sets a given disk scheduler for selected block devices. The setting persists across system reboots.

1. To see which profile is currently active, use: 

# tuned-adm active

2. Create a new directory for your TuneD profile:

 # mkdir /etc/tuned/ngx-profile

3. Collect the system unique identifier of the selected block device:

# udevadm info --query=property --name=/dev/sdb | grep -E '(WWN|SERIAL)' 
ID_SCSI_SERIAL=589c00fca0b3fa15 
ID_SERIAL=3589c00fca0b3fa15c9561490731619ef 
ID_SERIAL_SHORT=589c00fca0b3fa15c9561490731619ef 
ID_WWN=0x589c00fca0b3fa15 
ID_WWN_VENDOR_EXTENSION=0xc9561490731619ef 
ID_WWN_WITH_EXTENSION=0x589c00fca0b3fa15c9561490731619ef 
SCSI_IDENT_SERIAL=589c00fca0b3fa15

The command in the this example will return all values identified as a World Wide Name (WWN) or Serial Number associated with the specified block device.

4. Create the /etc/tuned/ngx-profile/tuned.conf configuration file. In the file, set the following options:

[disk]
devices_udev_regex=ID_WWN=0x589c00fca0b3fa15
elevator=none

To match multiple devices in the “devices_udev_regex” option, enclose the identifiers in parentheses and separate them with vertical bars:

[disk]
devices_udev_regex=(ID_WWN=0x589c00fca0b3fa15)|(ID_WWN=0x589c00...)
elevator=none

5. Enable the new ngx-profile and verify the settings:

# tuned-adm profile ngx-profile
# tuned-adm active
# tuned-adm verify

Setting the Disk Scheduler Using udev rule

This procedure sets a given disk scheduler for specific block devices using “udev rules”. The setting persists across system reboots.

1. Collect the system unique identifier of the selected block device:

# udevadm info --query=property --name=/dev/sdb | grep -E '(WWN|SERIAL)' 
ID_SCSI_SERIAL=589c00fca0b3fa15 
ID_SERIAL=3589c00fca0b3fa15c9561490731619ef 
ID_SERIAL_SHORT=589c00fca0b3fa15c9561490731619ef 
ID_WWN=0x589c00fca0b3fa15 
ID_WWN_VENDOR_EXTENSION=0xc9561490731619ef 
ID_WWN_WITH_EXTENSION=0x589c00fca0b3fa15c9561490731619ef 
SCSI_IDENT_SERIAL=589c00fca0b3fa15

2. Configure the udev rule. Create the /etc/udev/rules.d/99-ngxstorage.rules file with the following content: 

ACTION=="add|change", SUBSYSTEM=="block", ENV{ID_WWN}=="0x589c00fca0b3fa15", ATTR{queue/scheduler}="none"

 

We are strongly recommending below udev rule with NGX Storage. Applicable for RHEL 8.x and SuSE 15.2 and higher:

# IO Scheduler settings, reduce rng overhead,force rq_affinity the completion to run on the requesting cpu, set scsi device timeout 120.
ACTION=="add|change", SUBSYSTEM=="block", ENV{ID_WWN}=="0x589c00*", ATTR{queue/scheduler}="none" , ATTR{queue/add_random}="0", ATTR{queue/rq_affinity}="2" , ATTR{device/timeout}="120"

 

NGX Storage Recommended DM-Multipath Settings

The following /etc/multipath.conf file has been tested with recent versions of RHEL 8. It provides settings for volumes on NGX Storage exposed via either iSCSI or Fibre Channel. Prior to use, verify the configuration with multipath -t.  Some settings may be incompatible with older distributions.

defaults {
        polling_interval 5
        user_friendly_names yes
}
 
devices {

        device {
                vendor "NGX-IO.*"
                product "NGX-IO ISCSI"
                path_grouping_policy group_by_prio
                prio alua
                path_checker tur
                failback immediate
                no_path_retry queue
                flush_on_last_del yes
                dev_loss_tmo infinity
                detect_prio yes
        }
}

blacklist {
     wwid dcc2753ffa270f576957f426a0e944dd
}
multipaths {

    multipath {
        wwid                    3589c00 ...
        alias                   lun1
    }

    multipath {
        wwid                    3589c00 ...
        alias                   lun2
    }

    multipath {
        wwid                    3589c00 ...
        alias                   lun3
    }
 
    multipath {
        wwid                    3589c00 ...
        alias                   lun4
    }
 
}

 

Reference Links

 

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