Unlike most monitoring tools that either focus on a small set of statistics, format their output in only one way, run either interactively or as a daemon but not both, collectl tries to do it all. You can choose to monitor any of a broad set of subsystems which currently include buddyinfo, cpu, disk, inodes, InfiniBand, lustre, memory, network, nfs, processes, quadrics, slabs, sockets and tcp. Installing collectl The collectl community project is maintained at … [Read more...] about Troubleshooting performance issue in CentOS/RHEL using collectl utility
CentOS/RHEL 8
How to Configure VDO (Virtual Data Optimizer) filesystem to Persistently Mount at Boot
There are 2 ways in which this can be accomplished. 1. Using /etc/fstab 2. Using a Systemd Mount Unit File 1. Using /etc/fstab After device creation, the filesystem must be added to the /etc/fstab file to persistently mount. Below is an example /etc/fstab entry for a VDO device: # vi /etc/fstab # # /etc/fstab # Created by anaconda on Tue Nov 27 17:58:51 2018 # # Accessible filesystems, by reference, are maintained under '/dev/disk/'. # See man pages fstab(5), findfs(8), mount(8) … [Read more...] about How to Configure VDO (Virtual Data Optimizer) filesystem to Persistently Mount at Boot
How to create a VDO (Virtual Data Optimizer) device with the async/sync/auto write policy
Follow the steps below to create a VDO device with either the async, auto or sync write policy. 1. The write policy can be adjusted at creation time by using the --writePolicy option of the vdo command. For example, to create a VDO device with the sync write policy: # vdo create --name=vdosync --device=/dev/sdd --vdoLogicalSize=100G --writePolicy=sync Creating VDO vdosync Starting VDO vdosync Starting compression on VDO vdosync VDO instance 1 volume is ready at /dev/mapper/vdosync Or … [Read more...] about How to create a VDO (Virtual Data Optimizer) device with the async/sync/auto write policy
How to create xfs filesystem with 512 bytes block size
If you try to create a xfs filesystem with 512 bytes block size, you would get an error shown below: # mkfs.xfs -b size=512 [device] Minimum block size for CRC enabled file systems is 1024 bytes By default mkfs.xfs will enable CRC which forces a 1024 byte block. Turn off CRC to get 512 byte block. CRC enables enhanced error detection due to hardware issues, whilst the format changes also improve crash recovery algorithms and the ability of various tools to validate and repair metadata … [Read more...] about How to create xfs filesystem with 512 bytes block size
How to Recreate a VDO (Virtual Data Optimizer) index
What is an VDO index VDO uses a high-performance deduplication index called UDS to detect duplicate blocks of data as they are being stored. There are 2 types of UDS indexes available, namely: Sparse UDS index - In general, Red Hat recommends using a sparse UDS index for all production use cases. This is an extremely efficient indexing data structure, requiring approximately one-tenth of a byte of DRAM per block in its deduplication window. Dense UDS index - The default configuration of the … [Read more...] about How to Recreate a VDO (Virtual Data Optimizer) index
How to Increase the Physical Size of a VDO (Virtual Data Optimizer) Volume
If a VDO volume does not have enough physical space, it will send I/O errors to the layers above. The fix for which is to add more physical space to VDO. The VDO physical size is the amount of physical storage VDO can be used to write metadata and user data. Growing the physical size of VDO is often done when planning for growth or if the volume has run out of physical space. VDO volumes are grown online while the volume is active and the operating mode is normal. The command to grow … [Read more...] about How to Increase the Physical Size of a VDO (Virtual Data Optimizer) Volume
How to Configure a Storage Device to Use VDO (Virtual Data Optimizer) Deduplication and Compression
Step 1 - Identify the device for VDO exampansion Identify the storage device that will be used for the VDO volume. Make sure that the storage device is not being used for another purpose. # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 119.2G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 118.2G 0 part ├─rhel-root 253:0 … [Read more...] about How to Configure a Storage Device to Use VDO (Virtual Data Optimizer) Deduplication and Compression
How to Resize (Increase) Logical Size of a VDO (Virtual Data Optimizer) volume in CentOS/RHEL
The logical size or thin-provisioned size of a VDO volume can be grown to a maximum of 4 petabytes. A common reason for doing this is to make more logical space available for file systems and applications. Make sure that if you are using a file system or volume manager above VDO that they are resized, as well. VDO volumes are grown online while the volume is running. The command to grow logically is: # vdo growLogical --name=[vdo volume name] --vdoLogicalSize=[size] Example 1. View the … [Read more...] about How to Resize (Increase) Logical Size of a VDO (Virtual Data Optimizer) volume in CentOS/RHEL
How to install an RPM package into a different directory in CentOS/RHEL/Fedora
Identifying Relocatable Package Not all RPM packages can be installed into another directory. An RPM package that can be installed into a different directory is said to be relocatable. To check whether a particular package is relocatable, use the command: # rpm -qpi [rpm package] | head -1 For example, the packages: redhat-lsb-1.3-3.1.EL3.i386.rpm and rsync-2.5.7-5.3E.i386.rpm produces below output: # rpm -qpi redhat-lsb-1.3-3.1.EL3.i386.rpm | head -1 Name : redhat-lsb … [Read more...] about How to install an RPM package into a different directory in CentOS/RHEL/Fedora
How to add additional words to the password dictionary of pam_cracklib in CentOS/RHEL/Fedora
How can we add additional words to the list of words checked by password dictionary of pam_cracklib in Red Hat Enterprise Linux 6? What is PAM cracklib Red Hat Enterprise Linux can be configured to verify that passwords cannot be guessed easily. On Red Hat Enterprise Linux this check is performed by the Pluggable Authentication Module (PAM) /lib/security/pam_cracklib.so. It checks to ensure that passwords are a minimum length and verifies that a password does not occur in a … [Read more...] about How to add additional words to the password dictionary of pam_cracklib in CentOS/RHEL/Fedora