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diff --git a/posts/2021-01-15-root-on-zfs-a-zpool-of-mirror-vdevs-the-easy-way.html b/posts/2021-01-15-root-on-zfs-a-zpool-of-mirror-vdevs-the-easy-way.html deleted file mode 100644 index 01d25c8..0000000 --- a/posts/2021-01-15-root-on-zfs-a-zpool-of-mirror-vdevs-the-easy-way.html +++ /dev/null @@ -1,375 +0,0 @@ -<!DOCTYPE html> -<html lang="en"> - <head> - <link rel="stylesheet" href="/includes/stylesheet.css" /> - <meta charset="utf-8" /> - <meta name="viewport" content="width=device-width, initial-scale=1" /> - <meta - property="og:description" - content="The World Wide Web pages of Adam Carpenter" - /> - <meta - property="og:image" - content="https://nextcloud.53hor.net/index.php/s/Nx9e7iHbw4t99wo/preview" - /> - <meta property="og:site_name" content="53hor.net" /> - <meta - property="og:title" - content="Root on ZFS: A ZPool of Mirror VDEVs The Easy Way" - /> - <meta property="og:type" content="website" /> - <meta property="og:url" content="https://www.53hor.net" /> - <title>53hornet ➙ Root on ZFS: A ZPool of Mirror VDEVs The Easy Way</title> - </head> - - <body> - <nav> - <ul> - <li> - <a href="/"> - <img alt="home" src="/includes/icons/home-roof.svg" /> - Home - </a> - </li> - <li> - <a href="/info.html"> - <img alt="information" src="/includes/icons/information-variant.svg" /> - Info - </a> - </li> - <li> - <a href="https://git.53hor.net"> - <img alt="git" src="/includes/icons/git.svg" /> - Repos - </a> - </li> - <li> - <a href="/software.html"> - <img alt="software" src="/includes/icons/floppy-variant.svg" /> - Software - </a> - </li> - <li> - <a type="application/rss+xml" href="/rss.xml"> - <img alt="rss" src="/includes/icons/rss.svg" /> - RSS - </a> - </li> - </ul> - </nav> - - <article> - <h1>Root on ZFS: A ZPool of Mirror VDEVs</h1> - - <p class="description"> - I wanted/needed to make a root on ZFS pool out of multiple mirror VDEVs, - and since I'm not a ZFS expert, I took a little shortcut. - </p> - - <p> - I recently got a new-to-me server (yay!) and I wanted to do a - root-on-ZFS setup on it. I've really enjoyed using ZFS for my data - storage pools for a long time. I've also enjoyed the extra functionality - that comes with having a bootable system installed on ZFS on my laptop - and decided with this upgrade it's time to do the same on my server. - Historically I've used RAIDZ for my storage pools. RAIDZ functions - almost like a RAID10 but at the ZFS level. It gives you parity so that a - certain number of disks can die from your pool and you won't lose any - data. It does have a few tradeoffs however*, and for personal - preferences I've decided that for the future I would like to have a - single ZPool over top of multiple mirror VDEVs. In other words, my main - root+storage pool will be made up of two-disk mirrors and can be - expanded to include any number of new mirrors I can fit into the - machine. - </p> - - <p> - This did present some complications. First of all, - <code>bsdinstall</code> won't set this up for you automatically (and - sure enough, - <a - href="https://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html" - >in the handbook</a - > - it mentions the guided root on ZFS tool will only create a single, - top-level VDEV unless it's a stripe). It will happily let you use RAIDZ - for your ZROOT but not the more custom approach I'm taking. I did - however use - <code>bsdinstall</code> as a shortcut so I wouldn't have to do all of - the partitioning and pool setup manually, and that's what I'm going to - document below. Because I'm totally going to forget how this works the - next time I have to do it. - </p> - - <p> - In my scenario I have an eight-slot, hot-swappable PERC H310 controller - that's configured for AHCI passthrough. In other words, all FreeBSD sees - is as many disks as I have plugged into the backplane. I'm going to fill - it with 6x2TB hard disks which, as I said before, I want to act as three - mirrors (two disks each) in a single, bootable, growable ZPool. For - starters, I shoved the FreeBSD installer on a flash drive and booted - from it. I followed all of the regular steps (setting hostname, getting - online, etc.) until I got to the guided root on ZFS disk partitioning - setup. - </p> - - <p> - Now here's where I'm going to take the first step on my shortcut. Since - there is no option to create the pool of arbitrary mirrors I'm just - going to create a pool from a single mirror VDEV of two disks. Later I - will expand the pool to include the other two mirrors I had intended - for. My selections were as follows: - </p> - - <ul> - <li>Pool Type/Disks: mirror mfisyspd0 mfisyspd1</li> - <li>Pool Name: zroot</li> - <li>Partition Scheme: GPT (EFI)</li> - <li>Swap Size: 4g</li> - </ul> - - <p> - Everything else was left as a default. Then I followed the installer to - completion. At the end, when it asked if I wanted to drop into a shell - to do more to the installation, I did. - </p> - - <p> - The installer created the following disk layout for the two disks that I - selected. - </p> - - <pre> -<code> -atc@macon:~ % gpart show -=> 40 3907029088 mfisyspd0 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd1 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) -</code> -</pre> - - <p> - The installer also created the following ZPool from my single mirror - VDEV. - </p> - - <pre> -<code> -atc@macon:~ % zpool status - pool: zroot - state: ONLINE - scan: none requested -config: - - NAME STATE READ WRITE CKSUM - zroot ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - mfisyspd0p3 ONLINE 0 0 0 - mfisyspd1p3 ONLINE 0 0 0 - -errors: No known data errors -</code> -</pre> - - <p> - There are a couple of things to take note of here. First of all, - <em>both</em> disks in the bootable ZPool have an EFI boot partition. - That means they're both a part of (or capable of?) booting the pool. - Second, they both have some swap space. Finally, they both have a third - partition which is dedicated to ZFS data, and that partition is what got - added to my VDEV. - </p> - - <p> - So where do I go from here? I was tempted to just - <code>zpool add mirror ... ...</code> and just add my other disks to the - pool (actually, I <em>did</em> do this but it rendered the volume - unbootable for a very important reason), but then I wouldn't have those - all-important boot partitions (using whole-disk mirror VDEVS). Instead, - I need to manually go back and re-partition four disks exactly like the - first two. Or, since all I want is two more of what's already been done, - I can just clone the partitions using <code>gpart backup</code> and - <code>restore</code>! Easy! Here's what I did for all four remaining - disks: - </p> - - <pre> -<code> -root@macon:~ # gpart backup mfisyspd0 | gpart restore -F mfisyspd2` -</code> -</pre> - - <p> - Full disclosure, I didn't even think of this as a possibility - <a - href="ihttps://unix.stackexchange.com/questions/472147/replacing-disk-when-using-freebsd-zfs-zroot-zfs-on-partition#472175" - >until I read this Stack Exchange post</a - >. This gave me a disk layout like this: - </p> - - <pre> -<code> -atc@macon:~ % gpart show -=> 40 3907029088 mfisyspd0 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd1 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd2 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd3 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd4 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) - -=> 40 3907029088 mfisyspd5 GPT (1.8T) - 40 409600 1 efi (200M) - 409640 2008 - free - (1.0M) - 411648 8388608 2 freebsd-swap (4.0G) - 8800256 3898228736 3 freebsd-zfs (1.8T) - 3907028992 136 - free - (68K) -</code> -</pre> - - <p> - And to be fair, this makes a lot of logical sense. You don't want a - six-disk pool to only be bootable by two of the disks or you're - defeating some of the purposes of redundancy. So now I can extend my - ZPool to include those last four disks. - </p> - - <p> - This next step may or may not be a requirement. I wanted to overwrite - where I assumed any old ZFS/ZPool metadata might be on my four new - disks. This could just be for nothing and I admit that, but I've run - into trouble in the past where a ZPool wasn't properly - exported/destroyed before the drives were removed for another purpose - and when you use those drives in future - <code>zpool import</code>s, you can see both the new and the old, failed - pools. And, in the previous step I cloned an old ZFS partition many - times! So I did a small <code>dd</code> on the remaining disks to help - me sleep at night: - </p> - - <pre> -<code> -root@macon:~ # dd if=/dev/zero of=/dev/mfisyspd2 bs=1M count=100 -</code> -</pre> - - <p> - One final, precautionary step is to write the EFI boot loader to the new - disks. In - <a href="https://www.freebsd.org/doc/handbook/zfs-zpool.html" - >zpool admin handbook</a - > - it mentions you should do this any time you <em>replace</em> a zroot - device, so I'll do it just for safe measure on all four additional - disks: - </p> - - <pre> -<code> -root@macon:~ # gpart bootcode -p /boot/boot1.efifat -i 1 mfisyspd2 -</code> -</pre> - - <p> - Don't forget that the command is different for UEFI and a traditional - BIOS. And finally, I can add my new VDEVs: - </p> - - <pre> -<code> -root@macon:~ # zpool zroot add mirror mfisyspd2p3 mfisyspd3p3 -root@macon:~ # zpool zroot add mirror mfisyspd4p3 mfisyspd5p3 -</code> -</pre> - - <p>And now my pool looks like this:</p> - - <pre> -<code> -atc@macon:~ % zpool status - pool: zroot - state: ONLINE - scan: none requested -config: - - NAME STATE READ WRITE CKSUM - zroot ONLINE 0 0 0 - mirror-0 ONLINE 0 0 0 - mfisyspd0p3 ONLINE 0 0 0 - mfisyspd1p3 ONLINE 0 0 0 - mirror-1 ONLINE 0 0 0 - mfisyspd2p3 ONLINE 0 0 0 - mfisyspd3p3 ONLINE 0 0 0 - mirror-2 ONLINE 0 0 0 - mfisyspd4p3 ONLINE 0 0 0 - mfisyspd5p3 ONLINE 0 0 0 - -errors: No known data errors -</code> -</pre> - - <p> - Boom. A growable, bootable zroot ZPool. Is it easier than just - configuring the partitions and root on ZFS by hand? Probably not for a - BSD veteran. But since I'm a BSD layman, this is something I can live - with pretty easily. At least until this becomes an option in - <code>bsdintall</code> maybe? At least now I can add as many more - mirrors as I can fit into my system. And it's just as easy to replace - them. This is better for me than my previous RAIDZ, where I would have - to destroy and re-create the pool in order to add more disks to the - VDEV. Now I just create another little mirror and grow the pool and all - of my filesystems just see more storage. And of course, having ZFS for - all of my data makes it super easy to create filesystems on the fly, - compress or quota them, and take snapshots (including the live ZROOT!) - and send those snapshots over the network. Pretty awesome. - </p> - - <p> - * I'm not going to explain why here, but - <a - href="http://www.openoid.net/zfs-you-should-use-mirror-vdevs-not-raidz/" - >this is a pretty well thought out article</a - > - that should give you an idea about the pros and cons of RAIDZ versus - mirror VDEVs so you can draw your own conclusions. - </p> - </article> - </body> -</html> |