Multipath IO Configuration

This page explains how to configure multipath I/O on Windows, VMware and Linux hosts that connect to QuantaStor over iSCSI or Fibre Channel. With multipathing configured, each storage volume appears to the host as one device that fails over between paths.

Understanding MPIO with QuantaStor

QuantaStor supports round-robin active/active multipathing through Microsoft MPIO on Windows and the device-mapper multipath (DMMP) driver on Linux. Multipathing spreads I/O across the paths to a volume and fails over to the remaining paths when a network connection on the host or the storage system goes down. On a Fibre Channel HA pool, the paths through the node that owns the pool are active and the paths through the partner node are standby. When the pool fails over, the host moves I/O to the partner node's paths.

Put each iSCSI path on its own subnet or VLAN. Several IP addresses on one subnet do not give you separate paths. QuantaStor presents iSCSI on every iSCSI-enabled network interface by default, so the only QuantaStor-side setup is giving each interface an address on the right subnet.

For example, this configuration gives two network paths between QuantaStor and the host:

QuantaStor server IP configuration

10.0.1.121/24
10.0.2.121/24


Host Client IP Configuration

10.0.1.125/24
10.0.2.125/24

Once the network configuration is correct, configure multipathing on the host. The sections below cover the most common host operating systems.

QuantaStor supports SCSI-3 persistent reservations, so you can use it with Microsoft Failover Clustering, Hyper-V and other cluster software that needs SCSI-2 or SCSI-3 reservations.

Configuring Microsoft MPIO

For Windows Server failover clusters, Cluster Shared Volumes and Hyper-V on QuantaStor HA pools, see Windows MPIO for Failover Clusters and Hyper-V for the recommended MPIO setup and timer tuning; the steps below cover only adding the QuantaStor device string.

MPIO is a Windows Server feature and is not available on desktop editions of Windows. To open the MPIO properties, type MPIO in the Start menu search box, or open MPIO in Control Panel.

The string to add for QuantaStor is "OSNEXUS QUANTASTOR      ".

On the MPIO Devices tab, click Add and enter this string exactly:

OSNEXUS QUANTASTOR      
       ^          ^^^^^^

The '^' characters show where the spaces go. Enter the string in capitals, with one space between the words and exactly six trailing spaces after QUANTASTOR. Windows matches the string against the 8-character vendor field and the 16-character product field that QuantaStor reports. Without the six trailing spaces, the MPIO driver does not recognize QuantaStor volumes, and Disk Management shows one disk per path.

VMWare Special Note

VMware ESXi needs no multipathing changes. It handles iSCSI and Fibre Channel multipathing to QuantaStor with its default settings.

Configuring Linux Device-Mapper Multipath (DMMP)

After you install device mapper multipath on your Linux distribution, log in as root and add the following to /etc/multipath.conf. If the file already has defaults or devices sections, add these entries to them rather than creating second copies.

defaults {
        find_multipaths         yes
}

devices {
        device {
                vendor                  "OSNEXUS"
                product                 "QUANTASTOR"
                path_grouping_policy    multibus
                failback                immediate
                path_selector           "round-robin 0"
                rr_weight               uniform
                path_checker            tur
        }
}

By default, multipath-tools uses find_multipaths strict, and Debian and Proxmox VE keep that default. In strict mode it only creates a multipath device for a WWID already listed in /etc/multipath/wwids. A newly assigned QuantaStor volume can then appear as separate sd devices with no multipath device over them. With find_multipaths yes, it creates a multipath device for any volume it sees on two or more paths.

For Fibre Channel, enable ALUA by using this device entry in place of the one above:

devices {
        device {
                vendor                  "OSNEXUS"
                product                 "QUANTASTOR"
                prio                    alua
                hardware_handler        "1 alua"
                path_grouping_policy    group_by_prio
                failback                immediate
                no_path_retry           10
                rr_weight               uniform
                path_checker            tur
        }
}

Earlier versions of this page included getuid_callout and rr_min_io lines in these entries. Current multipath-tools ignores both options, so this page no longer includes them. Existing configurations that still contain them do not need changing.

Also add this blacklist_exceptions section. multipath-tools treats a device as blacklisted unless it has at least one udev property that matches a property exception. This entry keeps QuantaStor volumes off the blacklist.

blacklist_exceptions {
    property "(ID_SCSI_VPD|ID_WWN|ID_SERIAL)"
    device {
        vendor "OSNEXUS"
        product "QUANTASTOR"
    }
}

After you update the file, restart the multipath service:

service multipathd restart

Then run multipath -ll on the host. Each QuantaStor volume appears once as an OSNEXUS,QUANTASTOR device, with its paths listed beneath it. With the Fibre Channel entry, the paths through the node that owns the pool form the active path group.

Mount filesystems from the device under /dev/mapper/, not from /dev/sdX. A filesystem mounted from an sd device bypasses the multipath driver and gets neither the extra paths nor failover.

Related pages

• Windows MPIO for Failover Clusters and Hyper-V
• Proxmox Storage Plugin
• Storage Volumes