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Articles in Filesystems
Synology NAS Hacks
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I’ve been using various Synology NAS devices for many years now, and they’re great. Well, almost. There are a few rough spots that don’t thrill me. These consumer-grade devices are designed to be difficult to …
Inventorying NFS Mounts and Mount Options
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As time goes by, NFS mounts multiply like rabbits. Added by many different people over the years, these entries present a dizzying variety of mount options – most are a copy-paste job that makes little …
Keeping Abreast with Filesystem Changes
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The inotify is a Linux kernel sybsystem for notifying user-space applications of filesystem changes. I always thought this exceptionally handy utility was under-appreciated or at least underutilized.
Migrating Filesystems with Active Processes
I’ve run into an interesting challenge: I needed to migrate application data from a local filesystem to NFS without stopping the processes running in the original mountpoint. Here’s a basic overview of the process. This …
Check Filesystem Mount Status
Sometimes you just need to do a quick sanity check on the filesystem mount status to make sure everything in fstab is mounted and everything’s that mounted is in the fstab. If, like myself, you’re a fan …
Osync and DiffTree
Think of osync as a kind of rsync that is more suited for making backups. While rsync certainly has more options, osync takes a lot of the complexity out of writing a backup script with a few options that are …
Extending Swap on LVM2 Logical Volume
To grow swap on LVM you will need to temporarily disable the swap LV. This will leave without swap space, which may upset some applications (Oracle). So the first step should be to set up …
Celerra NFS/CIFS Mixed Permissions Mode
This is a quick reminder on how to configure a Celerra filesystem for dual NFS/CIFS access where Windows-side permissions would translate correctly to the NFS side. By default, Celerra datamover will mount filesystems in “Native” mode. In this case, a file or folder created by a Windows user via the CIFS share will take on the default Unix permissions on the NFS side: 755 for folders and 644 for files.
Dealing with Full Filesystems
Filled up filesystems is a recurring condition eating up sysadmin time on a regular basis. Some studies show that filesystems running out of space are responsible for most day-to-day issues handled by IT departments. Disk …
Quickly Grow EMC Celerra Filesystem
As we all know, Celerra and its kin can get a bit annoying with their “filesystem over 90%” warning emails. Enabling the “autoextend” feature for the filesystems is one option, but if you are a control …
Filesystem Performance Testing Using dd
Below is a simple script to test filesystem read/write performance using dd with varying blocksize parameter. This can be useful for testing local filesystems as well as network-mounted filesystems. The end result will be a …
Quick BTRFS Test on OpenSuse 12.2
The recent announcement from Suse Enterprise Linux that Btrfs was production-ready raised some suspicions. The last time I tested btrfs (not very long ago) the primary issues were excessive CPU utilization and filesystem space that seemed to disappear into nowhere. So, as a quick test, I put together an OpenSuse 12.2 (3.4.6-2.10-desktop, OpenSuse 12.2) 64-bit VM (ESX) with one dual-core vCPUs, 4GB RAM, the OS disk and a 6GB striped LVM filesystem consisting of 4 4-GB virtual disks.
Searching Large Network-Mounted Filesystems
Recently I ran into a small problem: I needed to find recently-modified files in a very large NFS filesystem. One of the high-level folders contained dozens of sub-folders with thousands of files in each. There is a significant performance penalty associated with placing such directory structures on network-mounted filesystems. Running the “find” command at the top of the filesystem would have taken over an hour and the problem here was not available bandwidth, but the time it takes for the “find” to request and receive attribute information for each folder and file.
Show Allocated / Used Filesystem Space Summary
On servers with many filesystems calculating filesystem space utilization summary can get very tedious. Below is a simple script that will summarize all filesystems and provide you will the totals for allocated and used space in GB.
Linux LVM: Reduce Filesystem and Logical Volume
The following example shows how to reduce the size of a filesystem mounted on an LVM logical volume. The instructions below are only for non-root filesystems. No reboot is required, but the filesystem will need to be unmounted. So, if there are any user applications using this filesystem, they will need to be stopped and the users will need to log out.
NFS “Not Owner” Error
The “not owner” error is displayed on the client system (usually Solaris) when attempting to mount an NFS share from a server. This error may appear even though the share is correctly exported and the client system has full access. If you are getting a “permission denied” error, then this article is not for you and you should check here instead.
Forcing Linux to Reboot
Until I branched out a few years ago from supporting Unix server to working with Linux clusters, I never really encountered this issue: you type “reboot”, “init 0”, or “shutdown” as root and… nothing happens. Or the system starts going down but then hangs on unmounting a filesystem or unloading a module. I think this happened once to a colleague of mine who was rebooting a Solaris server, but this is a common problem with Linux.
Testing Filesystem Performance with Bonnie++
Bonnie++ is a benchmark utility designed to test performance of hard drives and filesystems by simulating various types of disk I/O. Bonnie++ may be used to test local disks as well as network-mounted filesystems. It …
Dealing with ReiserFS bad blocks
The following is a procedure for recovering a ReiserFS filesystem with bad blocks. If this is a system FS and cannot be unmounted, the box needs to be booted from the latest version of Knoppix …
Mountpoint permission problem in Solaris
The following condition was originally discovered in OpenSolaris 11 (Bug ID: 4697677). This problem occurs when you do mkdir -m 700 on a mountpoint before mounting it. This superceeds whatever permissions you might give to …
Creating large AIX JFS filesystems
A quick note on creating large JFS filesystems on AIX: if the filesystem is 64Gb or might be expanded to over 64Gb any time in the future, make sure the NBPI (Number of Bytes Per …
Monitoring Veritas VM problems on Solaris
Several Veritas VM and system logs can be used to monitor and diagnose problems with the Volume Manager. An automated script can be used to grab the last few lines from these logs whenever a …
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