Dell PowerStore 3000T EMC PowerStore Host Configuration Guide - Page 35

Partition Alignment in Linux Use the fdisk command to create partition alignment on a PowerStore cluster volume. To align partitions on PowerStore cluster volumes that are presented to Linux hosts, use the default value (2048). Then, create a partition using the fdisk command to ensure that the file system is aligned. When you perform partition alignment, the logical device (/dev/mapper/) should be used rather than the physical device (/dev/). When multipathing is not used (for example in a virtual machine), the physical device should be used. The following example demonstrates using the fdisk command to create an aligned partition on a PowerStore cluster volume. [root@lg114 ~]# fdisk -cu /dev/mapper/ 368ccf098003f1461569ea4750e9dac50 Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel Building a new DOS disklabel with disk identifier 0x12d4e90c Changes will remain in memeory only, until you decide to write them. After that, of course, the previous content won't be recoverable. Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite) Command (m for help): p Disk /dev/mapper/3514f0c5b12a00004: 1649.3 GB, 1649267441664 bytes 255 heads, 63 sectors/track, 200512 cylinders, total 3221225472 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 16384 bytes / 65536 bytes Disk identifier: 0x12d4e90c Device Boot Start End Blocks Id System In this mode, rather than using "cylinders" for creating partitions, the fdisk command uses sectors, which are a direct mapping to the LBA space of the cluster. Thus, to verify that the partition is aligned, simply verify that the starting sector number is a multiple of 16 (16 sectors, at 512 bytes each, is 8 KB). The fdisk command defaults to a starting sector for the first partition of 2048, which is divisible by 16, and thus is correctly assigned. Creating a File System When creating a file system with PowerStore cluster storage, use its default block size, and disable UNMAP during creation. It is recommended to create the file system using its default block size (using a non-default block size may lead to unexpected behavior). Refer to your operating system and file system documentation. NOTE: Creating a file system with UNMAP enabled on a host connected to PowerStore may result in an increased amount of write I/Os to the storage subsystem. It is highly recommended to disable UNMAP during file system creation. To disable UNMAP during file system creation: • When creating a file system using the mke2fs command - Use the "-E nodiscard" parameter. • When creating a file system using the mkfs.xfs command - Use the "-K" parameter. For a more efficient data utilization and better performance, use Ext4 file system with PowerStore cluster storage instead of Ext3. For details on converting to Ext4 file system (from either Ext3 or Ext2), refer to https://ext4.wiki.kernel.org/index.php/UpgradeToExt4. NOTE: File system configuration and management are out of the scope of this document. Host Configuration for Linux 35