Image of the glider from the Game of Life by John Conway
Skip to content

{ Category Archives } Linux

Linux news and information.

ZFS Administration, Part V- Exporting and Importing zpools

Our previous post finished our discussion about VDEVs by going into great detail about the ZFS ARC. Here, we'll continue our discussion about ZFS storage pools, how to migrate them across systems by exporting and importing the pools, recovering from destroyed pools, and how to upgrade your storage pool to the latest version. Motivation As […]

ZFS Administration, Part IV- The Adjustable Replacement Cache

Our continuation in the ZFS Administration series continues with another zpool VDEV call the Adjustable Replacement Cache, or ARC for short. Our previous post discussed the ZFS Intent Log, or ZIL and the Separate Intent Logging Device, or SLOG. Traditional Caches Caching mechanisms on Linux and other operating systems use what is called a Least […]

ZFS Administration, Part III- The ZFS Intent Log

The previous post about using ZFS with GNU/Linux concerned covering the three RAIDZ virtual devices (VDEVs). This post will cover another VDEV- the ZFS Intent Log, or the ZIL. Terminology Before we can begin, we need to get a few terms out of the way that seem to be confusing people on forums, blog posts, […]

ZFS Administration, Part II- RAIDZ

The previous post introduced readers to the concept of VDEVs with ZFS. This post continues the topic discusing the RAIDZ VDEVs in great detail. Standards Parity RAID To understand RAIDZ, you first need to understand parity-based RAID levels, such as RAID-5 and RAID-6. Let's discuss the standard RAID-5 layout. You need a minimum of 3 […]

ZFS Administration, Part I- VDEVs

So, I've blogged a few times randomly about getting ZFS on GNU/Linux, and it's been a hit. I've had plenty of requests for blogging more. So, this will be the first in a long series of posts about how you can administer your ZFS filesystems and pools. You should start first by reading how to […]

How A ZIL Improves Disk Latencies

I just setup an SSD ZFS Intent Log, and the performance improvements have been massive. So much so, I need to blog about it. But first, I need to give you some background. I'm running a 2-node KVM hypervisor cluster replicating the VM images over GlusterFS (eventually over RDMA on a DDR InfiniBand link). One […]

How Much Swap?

I've been in the UNIX and GNU/Linux world since 1999. Back then, hard drives were barely passing double digits in GB, and RAM was PC100 speed at roughly 128 MB max. In fact, it wasn't uncommon for most systems to have 32 MB of RAM with an 8 GB hard drive. And we ran GNOME, […]

Announcing Hundun

Per my last post, I decided to setup an entropy server that the community could use. So, I've done just that. That server uses 5 entropy keys from Simtec Electronics in the U.K. as its hardware true random number generators. It hands out high quality randomness for the most critical cryptographic applications. The purpose, is […]

The Entropy Server

With my last post about the entropy key hardware true random number generator (TRNG), I was curious if I could set this up as a server. Basically, bind to a port that spits out true random bits over the internet, and allow clients to connect to it to fill their own entropy pools. One of […]

Haveged Continued

I noticed that on my machine, my entropy was staying high, then falling off. Then, at what appeared to be some arbitrary point, it would fill back up, in a very periodic manner. This is, of course, after running haveged in the background. Curious, I started looking into it. It took a while to find. […]

Haveged - A True Random Number Generator

I admit that my last post sucked. I've been working on a few things that I want to blog about, but it's going to take time to get all my ducks in a row. So, that post was mostly "filler". Read as "I haven't blogged in a while, and should probably put something up". Sorry. […]

Encrypted ZFS Filesystems On Linux

This is just a quick post about getting a fully kernel-space encrypted ZFS filesystem setup with GNU/Linux, while still keeping all the benefits of what ZFS offers. Rather than using dmcrypt and LUKS, which would bypass a lot of the features ZFS brings to the table, encryptfs is our ticket. The reason this is so […]

Appropriate Use Of "kill -9 "

There are times when "kill -9" is the only time you can kill a PID that is behaving badly. However, it's usually not needed if you know your signals. When I encounter a badly behaving program, here is the procedure I usually take. First, I'll send a SIGTERM (kill -15) to the PID. Sometimes this […]

Network Gotcha

So, we were just recently troubleshooting a connectivity issue at the office. Some things seemed slow, other things seemed fast. It was hard putting a finger on it. So, we starting pinging random stuff, trying to figure out exactly what was going on. Is it routing? Is in DNS? Is it layer 2? What gives? […]

Libvirt, Tyan Motherboards, and UUID

I recently built two servers that I plan on using for a sandbox with various technologies (Infiniband, ZFS, RDMA, GlusterFS, Btrfs, Ceph, LXC, KVM, etc, etc, etc). So, getting everything installed and running, I ran into a rather interesting bug. I installed KVM and libvirt, and started rolling out some virtual machines. I wanted to […]