You might find it worth upgrading to 10gbps if you continue to go down this road. The Mikrotik CRS-309 has served me well, and a couple Intel X520-DA2s. I believe those NICs can do iSCSI natively, and pass the session to the operating system with iBFT.
SFP28 might be cheap enough now too, I'm not sure...
what i want to play with is rdma and having a bcache block device with the remote as a backing and a small local nvme as a write-through cache
I used similar ipxe setup for robotic cluster - every robot booted from the same thing, then kubernetes managed the containe orchestration. it was fun.
I know it was just a convenient pretext for a learning journey, but do not come away from this thinking llama.cpp needs to be compiled on Windows before use. The GitHib project has a cornucopia of pre-built artifacts to use.
Very neat. I've never seen the Debian installer using iscsi. No other installer either for that matter.
Looks like ZFS is only used to store the image on the server, though. I was expecting this to be more interesting because of that.
This man is diskless
something worth mentioning here is that iSCSI is quite unhappy on congested networks or packet loss caused by incast traffic.
to make this actually work well, consider modifying your switches QoS settings to carve out a priority VLAN for iSCSI traffic
or a north-south/east-west architecture, so there's an entirely separate network just for iSCSI. Control plane vs data plane.
I would probably recommend to look into NVMe over TCP over iSCSI, especially for fast NVMe drives.
"I didn’t want to get into the hassle of repartitioning everything that the boot loader works with both Linux & Windows."
Hmmh? I haven't done so in years, but configuring multi-boot used to be considerably easier than disk-less operation.
It is relatively easy to configure. Just install Linux after windows, and Linux will generally automatically setup a boot-selection screen for you. The installer should detect windows and even shrink the partitions for you.
You can install a prettier looking boot selection menu like rEFInd, but the default works just as well, and I think the mainstream distros all setup secure boot too. On my pc it was very easy, on my (8yr old) laptop I had to add some secure boot keys and the bios was very confusing, using terms that didn’t seem to match what they should have been.
My setup has worked almost entirely flawlessly and survived updates from both OSes. Only issue being “larger” windows feature updates putting windows back as the first OS in the list, but that happens maybe once or twice a year? And it’s a quick bios change to fix the order.
SecureBoot is a PITA.
For Debian and most other distros, secure boot isn't a problem. Installers are all using a signed, trusted-by-default bootloader.
There are some exceptions (some hardware from Microsoft doesn't trust the third party certificate used, for instance, and Red Hat Enterprise has their own root of trust if you opt into that), but they're very rarely ever an issue.
The Debian installer is less than optimal for repartitioning.
The Linux NTFS resizing code also has a tendency to trigger data corruption. Not really Linux' fault, but it's a good reason to do partitioning from inside of Windows, which can be a pain already.
Another issue I've run into is Windows creating a very small (~300MiB) EFI partition that barely fits the Windows bootloader, let alone a Linux bootloader and kernel. You can resize and recreate the partition of course, but reconfiguring Windows to use a different boot partition is a special kind of hell I try to avoid.
>Not really Linux' fault
If Linux corrupts someone files, it is 100% Linux's fault and is absolutely unacceptable.
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I have to admit, I misread "Diskless Linux" initially ...
Friends don't let friends use grub.
rEFInd is _so_ much simpler: one efi entry, one text config file in the efi partition, nothing that needs to change when the kernel updates, and no massive pile of templating and moving parts to mysteriously break dumping you at an impenetrable grub “rescue” shell.
Systemd-boot is my choice for any simple boot scenario. Love it. Agreed that grub is a mess
There's also systemd-boot, which seems to be getting more popular.
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Does zfs support error correcting instead of just finding (already) broken files?
I have been waiting for such a feature for like 15 years now. Without it, zfs is just a fad and useless filesystem (all that complexity for NOTHING).
ext2 for the win! still
I don't know if I'm understanding your question, but ZFS actively corrects data on disk when it finds a checksum error [0]. Those checksum errors can be found when accessing that data, or doing a 'scrub' action that scans the whole volume to check integrity.
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0: https://klarasystems.com/articles/troubleshooting-zfs-common-issues-how-to-fix-them/ZFS supports self healing, you do not have scrub, it will be corrected during a bad read as long you have a copy. Metadata has 2 copies by default for additional safety for a single disk.
Nice. I'm extra fond of ZFS backed network root filesystem, because it lets you put an OS on ZFS without needing to deal with ZFS support in that OS. (One of these days I want to try OpenBSD with its root on NFS on ZFS, either from Linux or FreeBSD.)
Does anyone have an opinion on iSCSI vs NBD?
Well, iSCSI is a standard, so chances are better that it's supported in a non-Linux OS, e.g. MS Windows. Years ago I booted a Windows (7, iirc) client that way, but gave up on it (too much hassle and performance limited by the network) when SSDs became cheap.
I think you need NBD if you're going to use glustre, but I could also be thinking of ceph.
You might like https://smolbsd.org/
Well yes, I do like that:), but I don't see the connection to this thread?
I don’t have direct experience, but when I looked into it my takeaway that NBD was unable to reliably deal with network interruptions as well as iscsi.
https://forums.gentoo.org/viewtopic.php?p=4895771&sid=f9b7ac...
https://github.com/NetworkBlockDevice/nbd/issues/93
Whether that’s the case with the latest version, I don’t know, but it’s something you might test if you choose to try it.
I've done a lot of headless/diskless stuff. I haven't done much for years, because my NAS only has gigabit Ethernet ports. I can cascade them and get four Gbps downstream, but it's still painful.
I have recently upgraded my house to 10Gbps Ethernet, with only one room still stuck at gigabit, and unfortunately, it's my main office. I'm working on getting the drop there now (literally, just taking a break here).
Even once I'm done, accessing an iSCSI drive over 10GbE will be 4-8 times slower than a local NVMe drive, but it will sure be a lot better than it was!
Ideally, I could run VMs on the NAS and have great performance, but that's another hardware upgrade...
Using a proper NIC (Chelsio) with their iSCSI accelerator will boost your iSCSI performance significantly. Another alternative is Mellanox with RDMA. You need CX4+ for optimal performance over TCP/IP, while the cheap CX3 is excellent with IPoIB. If you have a lot of packet drops and retransmissions, another option for boosting iSCSI performance is getting a network switch with a lot of memory for packet buffering. This helps with incast congestion. There are special switches with gigabytes of memory built for this.
NVMe-oF is the best protocol with least overhead for network drives, with a proper setup you lose only 10-20% latency compared to local disk even with Intel Optane. Throughput should be almost similar.
Really I wonder how this turns out to be diskless while you're clearly accessing a disk/drive over the network. Shouldn't we refer to this as network boot?
It's diskless from the point of view of the device being booted.
This could be an interesting setup for booting off a NAS like Synology or QNAP. I haven't really used iSCSI, it's intimidating how much prep this takes...
iSCSI seems intentionally obscure. One of the improvements I made to NBD was invent a simple, standardized URI format so that you can specify servers easily, eg:
nbdinfo nbd://server
nbdcopy nbd://server:2001/ nbd+unix:///?socket=/tmp/localsock
NBD looks pretty nice! I've been eyeing it from afar for a while.
How well does it work in environments with noticeable network latency?
The 'target' moves slow so once you learn it, it all stays relevant forever.
... And it's very, very fun.
Does it offer performance advantages over NFS root?
I kind of expect the performance is worse, but one neat thing is that iscsi is a block device, so you could run e.g. disk crypto, volume management or whatever on it. Not to mention any FS. And you don't need to deal with NFS or RPC.
Dunno about performance vs NFS, but I've stuffed an unaware OS onto ZVOL-over-iSCSI using a NIC with option ROM.
NFS diskless is the more common approach I've used but this is very cool.
When I tried root-on-nfs I had a lot of issues. The Redhat and Arch package managers don't seem to like it (presumably a sqlite thing?).
You can download the rootfs, extract it to a ramdisk, and just run in memory. This is fast for everything. Unfortunately, memory just got super expensive. Fortunately, Linux requires ~no memory to do many useful things.
NFS diskless was easier for me to setup when I was doing it.
THe caveat was, you needed readonly root, so that meant freezing the OS, anything that needed changing was either stored in a ram disk (that you need to setup) or a per host nfs area (kinda like overlayfs, but not)
Why would you need a read-only root? Do you mean to share across multiple machines?
Yeah it makes things a bit easier to debug. Originally my system was designed to run on multiple machines at once.
If you needed to update the root dir, you chrooted into it and did the (yum) update.
Pretty cool! You could also boot into an ephemeral minimal initrd that displays a selection menu instead of doing it in iPXE. That would grab the new kernel and initrd from the network and kexecs it without reboot.
> You could also boot into an ephemeral minimal initrd
Wouldn't that need a local disk?
No. PXE boots routinely load the kernel and initramfs directly into RAM with no local disk involved. The initramfs then mounts the real root FS over the network.
Then anaconda or whatover os installer picks up and installs the OS in a PXE install sequence when there is a local disk.
> UEFI fixes that to some extent, but it’s a pain to maintain the UEFI entries manually and change them every time the kernel updates.
… you don't have to update the UEFI entries every time the kernel updates. (I guess you might if you do like a kernel w/ CONFIG_EFI_STUB, and you place the new kernel under a different filename than what the UEFI boot entry point to then you might … but I was under the impression that that'd be kind of an unusual setup, and I thought most of us booting w/ EFI were doing so with Grub.)
I have 2 entries, /efi/current.efi and /efi/old.efi... when I upgrade, I copy current to old, and copy my new kernel out of /boot as current and reboot.
Even if you do CONFIG_EFI_STUB, there should be a post-update hook to automatically call efibootmgr.
or just copy the latest kernel to something like /vmlinux and /initramfs
Or use UKI and throw the current kernel to /efi/boot/bootx64.efi; there's plenty of solutions to sane bootloader/kernel management if you're willing to invest 15 minutes into the topic and not act like it's scary and complicated (it really is the opposite).
i never got it to work
Grub2 is scary and complicated. Remove grub from the equation, and all the scary goes away.
grub is just a operating system. it is quite good when shit hits the fan