Veritas InfoScale™ 7.4 Solutions Guide - Linux
- Section I. Introducing Veritas InfoScale
- Section II. Solutions for Veritas InfoScale products
- Solutions for Veritas InfoScale products
- Solutions for Veritas InfoScale products
- Section III. Stack-level migration to IPv6 or dual stack
- Section IV. Improving database performance
- Overview of database accelerators
- Improving database performance with Veritas Concurrent I/O
- Improving database performance with atomic write I/O
- Section V. Using point-in-time copies
- Understanding point-in-time copy methods
- Backing up and recovering
- Preserving multiple point-in-time copies
- Online database backups
- Backing up on an off-host cluster file system
- Database recovery using Storage Checkpoints
- Backing up and recovering in a NetBackup environment
- Off-host processing
- Creating and refreshing test environments
- Creating point-in-time copies of files
- Section VI. Maximizing storage utilization
- Optimizing storage tiering with SmartTier
- Optimizing storage with Flexible Storage Sharing
- Optimizing storage tiering with SmartTier
- Section VII. Migrating data
- Understanding data migration
- Offline migration from LVM to VxVM
- Offline conversion of native file system to VxFS
- Online migration of a native file system to the VxFS file system
- VxFS features not available during online migration
- Migrating storage arrays
- Migrating data between platforms
- Overview of the Cross-Platform Data Sharing (CDS) feature
- CDS disk format and disk groups
- Setting up your system to use Cross-platform Data Sharing (CDS)
- Maintaining your system
- Disk tasks
- Disk group tasks
- Displaying information
- File system considerations
- Specifying the migration target
- Using the fscdsadm command
- Maintaining the list of target operating systems
- Migrating a file system on an ongoing basis
- Converting the byte order of a file system
- Migrating from Oracle ASM to Veritas File System
- Section VIII. Just in time availability solution for vSphere
- Section IX. Veritas InfoScale 4K sector device support solution
- Section X. Reference
Using FileSnaps to optimize write intensive applications for virtual machines
When virtual machines are spawned to perform certain tasks that are write intensive, a significant amount of unsharing can take place. Veritas recommends that you optimize performance by enabling lazy copy-on-write. If the use case does not allow enabling lazy copy-on-write, with careful planning, you can reduce the occurrence of unsharing. The easiest way to reduce unsharing is to separate the application data to a file other than the boot image. If you cannot do this due to the nature of your applications, then you can take actions similar to the following example.
Assume that the disk space required for a boot image and the application data is 20 GB. Out of this, only 4 GB is used by the operating system and the remaining 16 GB is the space for applications to write. Any data or binaries that are required by each instance of the virtual machine can still be part of the first 4 GB of the shared extent. Since most of the writes are expected to take place on the 16 GB portion, you should allocate the master image in such a way that the 16 GB of space is not shared, as shown in the following commands:
# touch /vdi_images/master_image # /opt/VRTS/bin/setext -r 4g -f chgsize /vdi_images/master_image # dd if=/dev/zero of=/vdi_images/master_image seek=20971520 \ bs=1024 count=1
The last command creates a 20 GB hole at the end of the file. Since holes do not have any extents allocated, the writes to hole do not need to be unshared.