Key Points to remember before you create your Red Hat Gluster Storage 3.0 trusted pool

You should follow Administration Guide - Configuring and Managing Red Hat Storage Server 3.0

Some Key points to remember :

• You should not create Red Hat Storage volume bricks using raw disks. Bricks must be created on thin-provisioned Logical Volumes (LVs). This is also recommended because Red Hat Storage Server 3.0 has snapshot feature which is based on LVM snapshot feature.
• Red Hat supports formatting a Logical Volume using the XFS file system on the bricks and you should not use any other local filesystem.
• In Red Hat Storage Server 3.0 each brick should be mapped to single thin-provisioned Logical Volume (LV) because of snapshot feature.
• Bricks should be of same size as of now Red Hat Storage Server does not support bricks of different sizes. This feature might be added in future releases.
• The RAID levels that are most commonly recommended are RAID 6 and RAID 10. RAID 6 provides better space efficiency, good read performance and good performance for sequential writes to large files. For 12 disks, RAID 6 volume can provide ~40% more storage space as compared to RAID 10 volume, which will have 50% reduction in capacity. However, RAID 6 performance for small file writes and random writes tends to be lower than RAID 10. If the workload is strictly small files, then RAID 10 is the optimal configuration.
• You can make use of Red Hat Access Lab - File System Layout Calculator App for RAID and filesystem configuration.
• You can also look into how new bricks and thin lv pool and lvs setup for RHSS-3.0 is different from old bricks and lvs setup for RHSS-2.1-variant-1 and old bricks and lvs setup for RHSS-2.1-variant-2 with the help of given diagrams.
• For more details on What are the recommended RAID, LVM, and filesystem configurations for the backend bricks for Red Hat Storage Server volumes?.
• It is always recommended to follow Configuring Red Hat Storage for Enhancing Performance Section in Administration Guide.

• XFS Inode Size :
  As the Red Hat Storage makes extensive use of extended attributes, an XFS inode size of 512 bytes works better with Red Hat Storage than the default XFS inode size of 256 bytes. So, inode size for XFS must be set to 512 bytes, while formatting the Red Hat Storage bricks. To set the inode size, you need to use -i size option with the mkfs.xfs command.

  To format the bricks to the supported XFS file system format :
  # mkfs.xfs -i size=512 -L FS_LABEL DEVICE 
  Here, FS_LABEL is a file-system label and DEVICE is the created thin LV. 
  The inode size is set to 512 bytes to accommodate for the extended attributes used by Red Hat Storage. 
  

• Allocation Strategy:
  inode32 and inode64 are two most common allocation strategies for XFS. With inode32 allocation strategy, XFS places all the inodes in the first 1 TiB of disk. inode32 allocation strategy is used by default. With inode64 mount option inodes would be replaced near to the data which would be minimize the disk seeks.

• Access Time:
  If the application does not require to update the access time on files, than file system must always be mounted with noatime mount option.

• For Example entry of a brick should look like as below given in /etc/fstab :

   /dev/vg_bricks/lv_exp1    /mountpoint  xfs     defaults,inode64,noatime,nouuid  1  2
  

• Performance tuning option in Red Hat Storage:
  Run the following command after creating the volume:

   # tuned-adm profile default ; tuned-adm profile rhs-high-throughput
       Switching to profile 'default' 
       Applying ktune sysctl settings: 
       /etc/ktune.d/tunedadm.conf:                           [  OK  ] 
       Applying sysctl settings from /etc/sysctl.conf  
       Starting tuned:                                       [  OK  ] 
       Stopping tuned:                                       [  OK  ] 
       Switching to profile 'rhs-high-throughput'
  
       This profile increases read ahead to 64 MB, changes I/O scheduler to deadline and disables power-saving mode .
  

Once Your Red Hat Storage Server 3.0 cluster architecture is ready you can get it reviewed by following Red Hat Storage Server 3 Architecture Review Process.