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27 Dell EMC SC Series: Red Hat Enterprise Linux Best Practices | CML1031
no_path_retry can be set to fail if it is preferable to fail the I/Os and let the applications to handle the errors.
In which case, I/Os fail immediately and are not queued when all paths become unavailable.
Within the devices section, locate the COMPELNT device definition and change the following attributes.
features 0
no_path_retry fail
To implement this to specific device at runtime, issue the following command for the desired multipath device.
# dmsetup message /dev/mapper/vol_001 0 "fail_if_no_path"
3.7 LUN partition
Partition tables are not required for volumes other than the boot drive. It is recommended to use SC Series
provisioned volumes as whole drives unless the applications requires the use of partitions. Filesystems, such
as ext4 and xfs, and applications, such as Logical Volume Manager and Oracle ASM, can manage whole
drives more efficiently without partitions. This leverages the native strengths of the SC Series array in wide-
striping volumes across all disks in the tier from which the volume is provisioned. Additionally, the use of
partition tables may pose challenges when expanding the volumes capacity. Either fdisk or parted can be
used to create the partition. However, only parted can create partitions larger than 2 TB.
3.7.1 Partition alignment
When partitioning a LUN, it is recommended to align the partition on the 1M boundary for optimal
performance. Misalignment can cause excessive I/Os and degrade overall performance of the system.
3.7.2 Creating and validating partition using parted
Specify the partition offset at 2048 sector (1M). The following command creates a single partition that takes
up the entire LUN. Once the partition is created, the partition file /dev/mapper/testvol1 becomes available for
creating file system or application volume.
Create a partition:
# parted -s /dev/mapper/testvol mklabel gpt mkpart primary xfs 2048s 100%
Validate the partition:
# parted /dev/mapper/testvol align-check opt 1
1 aligned
List partitions:
# parted /dev/mapper/testvol print
Model: Linux device-mapper (multipath) (dm)
Disk /dev/mapper/testvol: 10.7GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1049kB 10.7GB 10.7GB primary