Date: Mon, 25 Mar 2013 14:55:02 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: John Nielsen <lists@jnielsen.net> Cc: "stable@FreeBSD.org" <stable@freebsd.org> Subject: Re: Virtio and GEOM labels Message-ID: <D69236D7-FC15-48AA-B2C9-DEAA43835060@gromit.dlib.vt.edu> In-Reply-To: <44809413-C1A4-4A0E-8598-B88651A16A8F@jnielsen.net> References: <D5454720-6D16-4D42-8A13-7E6B29126180@gromit.dlib.vt.edu> <44809413-C1A4-4A0E-8598-B88651A16A8F@jnielsen.net>
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On Mar 25, 2013, at 1:46 PM, John Nielsen <lists@jnielsen.net> wrote: > On Mar 22, 2013, at 8:14 AM, Paul Mather <paul@gromit.dlib.vt.edu> = wrote: >=20 >> I'm running FreeBSD 9-STABLE as a guest under RHEL 6.4 KVM = virtualisation. I have networking and storage in the FreeBSD guest = using the Virtio drivers (with the virtual disk set to "Virtio" in the = definition on the host). Everything is working nicely: I have a vtnet = network adapter and see vtbd devices for my virtual disks in FreeBSD. = Performance is much better compared with an emulated IDE device. >=20 > I've had the same experience. >=20 >> The odd thing is that I don't see GEOM labels reflected in /dev. For = example, I have GPT labels defined in the guest, but I don't see them = show up under /dev/gpt. Similarly, my UFS labels don't show up under = /dev/ufs. I *do* see a /dev/gptid. That appears to be the only label = that shows up. >=20 > I have not encountered this issue. I use virtio block devices and GPT = labels exclusively in multiple FreeBSD 9.1 guests and all mount/function = without issue. How are you referring to your filesystems in /etc/fstab? = IIRC GEOM makes not-in-use labels disappear when a device is in use = (e.g. mounted). If you take a new device, put a labeled GPT partition on = it and a labeled UFS partition on that but don't mount anything, what = happens? Thanks for the reply. My apologies: this is a case of pilot error on my part. I was mounting = the devices as /dev/vtbd... I hadn't realised that the = present-but-unused labels were being suppressed when the device was = mounted. Has this always been the case? For some reason I had a = distinct recollection stuck in my mind that all labels showed up in = /dev. Anyway, many thanks for pointing the way to the solution. I now have = GPT- and UFS-labelled devices mounted in my FreeBSD guest system. >=20 >> Is there something special I need to do to get GPT and UFS labels to = appear when using Virtio? It seems to me that Virtio block devices = appear to be somewhat unusual. Unlike regular ATA and SCSI devices, my = vtbd devices don't appear in the boot dmesg (although a vtblk device = does), and "camcontrol devlist" does not list them. It's not clear to = me how I am supposed to interact with them other than via basic device = I/O through /dev/vtbdX. I thought that the virtio_scsi module might = make them appear as "da" devices and able to interacted with via = camcontrol, but this doesn't seem to be the case. >=20 > Virtio block devices and virtio SCSI devices are not the same. If you = want to use the virtio_scsi module in FreeBSD you should expose a virtio = SCSI device from the host. Thank you for the explanation. I've been using virt-manager up to now = for setting up KVM guests and it seems that virtio-scsi isn't exposed = through that interface---only through the command line. I'll have to = investigate... Cheers, Paul.
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