ZFS compression: yes, you want this
Published by Jim Salter // February 24th, 2015
So ZFS dedup is a complete lose. What about compression? Compression is a hands-down win. LZ4 compression should be on by default for nearly anything you ever set up under ZFS. I typically have LZ4 on even for datasets that will house database binaries… yes, really. Let’s look at two quick test runs, on a Xeon E3 server with 32GB ECC RAM and a pair of Samsung 850 EVO 1TB disks set up as a […]
Read MoreZFS dedup: tested, found wanting
Published by Jim Salter // February 24th, 2015
Even if you have the RAM for it (and we’re talking a good 6GB or so per TB of storage), ZFS deduplication is, unfortunately, almost certainly a lose. I don’t usually have that much RAM to spare, but one server has 192GB of RAM and only a few terabytes of storage – and it stores a lot of VM images, with obvious serious block-level duplication between images. Dedup shows at 1.35+ on all the datasets, […]
Read MoreExploring Copyleft
Published by Jim Salter // February 11th, 2015
Recently, the ElementaryOS Linux distribution screwed the pooch pretty badly, PR-wise – TL;DR if ElementaryOS nerfs the blog post they never should have made: “if you don’t donate money when you download ElementaryOS, you’re a cheater”. Yeah, that didn’t go down so well. Where it got interesting was this Reddit thread discussing the gaffe. It never ceases to amaze me what a slippery concept copyleft really is, and how easy it is for people to […]
Read MoreZFS: You should use mirror vdevs, not RAIDZ.
Published by Jim Salter // February 6th, 2015
Continuing this week’s “making an article so I don’t have to keep typing it” ZFS series… here’s why you should stop using RAIDZ, and start using mirror vdevs instead. The basics of pool topology A pool is a collection of vdevs. Vdevs can be any of the following (and more, but we’re keeping this relatively simple): single disks (think RAID0) redundant vdevs (aka mirrors – think RAID1) parity vdevs (aka stripes – think RAID5/RAID6/RAID7, aka […]
Read MoreWill ZFS and non-ECC RAM kill your data?
Published by Jim Salter // February 3rd, 2015
This comes up far too often, so rather than continuing to explain it over and over again, I’m going to try to do a really good job of it once and link to it here. What’s ECC RAM? Is it a good idea? The ECC stands for Error Correcting Checksum. In a nutshell, ECC RAM is a special kind of server-grade memory that can detect and repair some of the most common kinds of in-memory […]
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