I read this post about upgrading an older SC826 to support the rear drive cage option, and wondered if I could do the same with an SC847. The newer ‘B’ models support this natively, but there are still tons of cheap non-B models out there.

The first question is “why”? To which there are several answers:

• More drives! Free up a couple 3.5″ bays for 3.5″ drives, rather than using an entire 3.5″ bay for a 2.5″ drive.
• Cheapest NVMe option. $60-65 for the upgraded motherboard tray, and $80-90 for the drive cage, compared to $200 or so for the 4x U.2 rear backplane.
• More NVMe. You could get both the 4x U.2 rear backplane (BPN-SAS3-826EL1-N4) and the rear 2x NVMe cage for 6 NVMe bays. (There is also an 8x U.2 front backplane, but it’s hard to find). for a little over $200. The 8x U.2 front backplane is much more difficult to find. Maybe 4 NVMe bays isn’t quite enough for you.
• Dual-expander (EL2) backplanes: There are no backplane options with both dual SAS expanders and NVMe support.

Enough intro, I was able to get this conversion working, and it was much easier than the 826 conversion (though took a lot longer). Here’s how.

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It’s very useful to be able to see the sale history for an item that isn’t yours. You might want to see how quickly it sells, or whether offers are likely to be accepted or rejected. Unfortunately, eBay seems to have recently removed this link. The good news is that the page still exists and can be accessed via the same URL as before. Here’s a GreaseMonkey script to turn the “x sold” text into a clickable link like it previously was:

// ==UserScript== 
// @name     Restore eBay sold items link 
// @version  1
// @grant    none
// @match *://*.ebay.com/itm/*
// ==/UserScript==

element = document.querySelector("div.d-quantity__availability span:last-child, div.x-quantity__availability span:last-child")
text = element.textContent
re = /(.*)\/itm\/([0-9]+).*/
url = document.location.href.replace(re, '$1/bin/purchaseHistory?item=$2')
element.innerHTML = '<a href="' + url + '">' + text + '</a>'

I have not tested it on other userscript plugins. The end result looks like this:

Clicking the link takes you to the sale history page:

The 9400 series is LSI/Avago/Broadcom’s first “Tri-Mode” HBA, capable of supporting SAS, SATA, and NVMe all in one adapter. There’s a few catches, but despite that, it might still be worth the buy depending on your circumstances.

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Alt-Shift-3 in Bash inserts a ‘#’ at the beginning of the line, and then runs it. # is the comment character, so running it does nothing. So why would you want to do this?

The simplest use case is when you have a command typed out, but you realize there’s another command you need to run first. By pressing alt-#, you push the command into your history, so you can quickly recall it after running whatever other commands first.

Example:

# Set some dataset properties...but wait, what was the name of the dataset again?
# I have the whole line except for the dataset ready, so press Alt-#
$ #zfs set primarycache=none secondarycache=metadata tank3/
# It's in my bash history now, so I can run whatever other commands first
$ zfs list
...
# Okay, figured it out, so now I press up-arrow/^P (or search with ^R) to recall the command, then home/^A to go to the start of the line, then del/^D to remove the #
$ zfs set primarycache=none secondarycache=metadata tank3/path/to/my/data/set

A few months ago, I was getting some permissions errors when trying to create new VMs with virt-install. My main symptom was that I would get this error:

Could not open '/var/lib/libvirt/qemu/nvram/openwisp_VARS.fd': Permission denied

I recently tracked it down to an AppArmor profile issue. Fixing it was simple. I appended the following to /etc/apparmor.d/abstractions/libvirt:

  /var/lib/libvirt/qemu/nvram/** rwk,  
  /usr/share/OVMF/** rk,

This will also fix some other errors, such as the ‘Failed to lock byte 100’ and ‘cannot load apparmor profile’ errors.

I was able to get my Omnia to talk to a MikroTik CRS305 at 2.5Gbps via an SFP DAC, in this forum post.

Short version: You need to force 2.5Gbps on both sides (disable auto-negotiation). Doing so requires the other side to have a switch/NIC ASIC that can talk to the SFP+ module at 2.5Gbps (this is not always supported – even if you were to run 2.5GBASE-T off a transceiver, the ASIC and transceiver may still be communicating at a higher rate). In other words, this isn’t going to work on all hardware. For the long version, read on.

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I wanted to give a heads up of a couple specific issues from running OpenWRT in such a configuration from the previous post.

First, this script is incredibly useful. OpenWRT has neither udev rules nor systemd’s device naming scheme. Thus, it is likely you will break things as you play around with virtual interfaces, since interfaces may get different ethX names as they get rearranged. The mac-static-interfaces script gives you an easy way around this, on top of letting you give descriptive names to each device (for example, I named mine gb-top, gb-bottom, tengb-top and tengb-bottom).

Secondly, the default OpenWRT x86 does not have journaling enabled on its filesystem. This is bad, because it also won’t try to fsck a bad FS – it will just mount it read-only. This can be a problem for a variety of reasons, but the best fix is to simply enable journaling with the command tune2fs -j /dev/vda2 (or whatever your device is). This will cause a simple journal recovery to be performed rather than a read-only mount.

Something I’d like to try is using a KVM direct kernel boot, bypassing the bootloader entirely. This would allow for easy kernel and kmod updates.

If you’re not familiar, SR-IOV is a technology that allows you to expose a single physical network device (or more accurately, “physical function”) as multiple virtual functions (VFs). Each VF is a separate logical PCIe device, so a board equipped with an IOMMU should be able to pass them into VMs individually. This allows for basically the same level of performance as a passthrough of an entire PCIe device, but still allows it to be shared amongst many VMs. At the hardware level, it acts as essentially a network switch, instead of doing that in software like with typical virtual NICs.

Now, in my previous post, I talked about some of the new hardware going into my new router. The star of the show is the X10SDV-8C-TLN4F. So why not run OpenWRT baremetal on here? A few reasons:

1. Sometimes, you have to reboot. Rebooting a board like this can take several minutes. Not good for uptime. Meanwhile, a VM takes about 20 seconds to reboot fully. A custom kernel plus bypassing the bootloader (either via efistub or KVM direct kernel boot) could probably get it down to 10 seconds.
2. Lockouts – if you screw up your network configuration, it can be annoying to get back in. Not impossible, since it still has a VGA port and USB ports, but it’s definitely nicer to be able to still access the host and fix the VM from there.
3. OpenWRT isn’t necessarily going to have support for every bit of hardware on a board like this. It may lack drivers, or userland applications necessary to control said hardware. e.g. IPMI tools are lacking.
4. I can easily benchmark routing performance using virtual networks.
5. Since I can run ZFS on the host, I get ZFS snapshots and all that.

But….was it difficult? Was it worth it?

Yes and yes.

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Yet another SFP+ dual port 10GbE NIC.

Good:

• Works fine. Much less disastrous than the last review.
• Supports manipulating link state for VFs (e.g. so you can have VMs talk to each other even if the external link is down)
• Supports multiple PFs per physical port
• Lots of settings governing the internal switching and such
• If you don’t need SR-IOV, it has an “ultra low latency” mode

Bad:

• Requires standalone program to do configuration. alien worked fine, but be aware that there is no official version for Debian-based systems. However, once you apply a configuration you want to the card, it will persist. Once you get it close enough, you can use sysfs and ip to do the rest (e.g. configuring number of VFs and VF properties).
• Some setting changes require hard reboots.
• Doesn’t appear to support trusted VFs. This unfortunately would make it inappropriate for certain tasks, like the router build.
• Poor support for modern Windows versions. The driver and utilities package installed, but would BSOD consistently.

Overall:

• Not a terrible choice if you just need a good 10GbE NIC for Linux
• Don’t buy for Windows or if you need special SR-IOV features

Not that this is an unpopular take or anything, but this story reinforces reinforces my opinion that cable modems are the single worst piece of network equipment out there.

Several years ago, I had Xfinity’s 40Mbit downstream package. This just wasn’t cutting it, so I upgraded to the 400m down plan – the fastest they had at the time. I even got a promo rate on the upgrade. One minor problem – a rep told me that my current modem, a Cisco, would be sufficient, but this turned out to not be true – it could only do 300-some down. So I did some research, and bought the Arris SB8200. It was on Xfinity’s list of supported modems, and could do 2Gb/s down – plenty of headroom for future upgrades. Of course, since it only has gigabit Ethernet ports, you’d need to use link aggregation to actually get the full 2Gbps. OpenWRT didn’t have great support for bonding back then (it was doable, but not through UCI), but I figured that by the time it became an issue, that would change anyway.

Fast-forward a bit. The fastest speed they offer is now a gigabit. And they’re offering a promotional rate on it! On top of that, my current setup is good for 1g down, so no need to change out any hardware. Seems like a win-win!

Then, a bit later, my speed gets bumped up to 1.2Gb/s down, for free! Unfortunately, while it might have been doable, this meant it was probably time for the Omnia to be demoted to AP duty, and a new primary router would take its place (TODO put link). It’s easy – just set up the new router (which would be a breeze now that UCI supports bonding), enable link aggregation on the modem, and bam, 1200Mb/s down.

And it worked!

Since the router, desktop, and home server all have 10GbE interfaces, I was, for the first time, able to get >1Gbps downstream speeds.

For about 24 hours, that is. Stick around for the clownshow!

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