[ale] Xen Server adding a virtual disk to a VM

[Jim Kinney]

I use LVM for vm disks as well as physical ones. I am often needing to
expand the virtual disk space and LVM makes is easy.

On Oct 17, 2016 2:51 PM, "Scott Plante" <splante at insightsys.com> wrote:

> Thanks guys. This thread has been very informative.
>
> So you don't LVM inside a VM, but do you partition? I've always
> partitioned because it's how I was taught (pre-VM), but suppose you have a
> Linux VM, and you want to add a 200GB partition for some application. You
> go into your VM software and create the virtual disk and attach it to the
> VM. Inside the VM it appears as a new device, say /dev/xvde. You could
> create a partition and /dev/xvde1 would appear and you could mkfs
> /dev/xvde1 or you could skip the partitioning and just mkfs /dev/xvde. One
> reason you generally partition is for the sector alignment stuff, but
> (correct me if I'm wrong) that doesn't apply to a virtual disk. The sector
> alignment would be taken care of when you partition the drive inside
> XenServer, VMWare or whatever's running on the bare metal. Another reason
> you might normally partition a drive is to separate your OS  from your
> data, to make sure run-away log files don't crash your database, etc., but
> that doesn't apply here because you've already created a separate virtual
> disk for that purpose.
>
> I asked a friend at the pub Friday night who works with lots of VMs and he
> says he partitions just as a reminder to himself that he has or hasn't done
> something with the virtual disk. So he might go add a new disk to a
> half-dozen VMs, and when he goes into each one he can more easily tell
> whether he has taken care of it yet or something like that. If I add or
> remove a disk once a month it's a lot, so that's not a big selling point
> for me. Still, I suppose it could be useful as some longer term
> "documentation" kind of thing.
>
> So those of you on the list who deal with VMs: do you partition your
> virtual disks?
>
> Scott
>
> p.s. my recent VM experience is mostly with XenServer, so forgive me if my
> question and/or terminology doesn't make sense for ESXi, KVM, or other VM
> environments.
>
> ------------------------------
> *From: *"Phil Turmel" <philip at turmel.org>
> *To: *ale at ale.org
> *Sent: *Saturday, October 15, 2016 11:08:35 AM
> *Subject: *Re: [ale] Xen Server adding a virtual disk to a VM
>
> On 10/14/2016 05:13 PM, DJ-Pfulio wrote:
> > Ok, so fdisk was patched, but I'm still waiting for that patch to
> > actually make it into every distro I see. I keep seeing fdisk complain
> > about GPT disks - easier to just use parted, IMHO. Parted also aligns
> > partitions correctly, as does gparted.  fdisk does not. If you use only
> > SSDs, don't think that it matters, but on spinning disks, there can be a
> > real, noticeable, performance hit.
>
> Interesting.  I've been using 'gdisk' for quite some time now.  Same
> style of interface but supports GPT, plus conversions to/from MBR and
> BSD.  I thought is was packaged with util-linux, but I just found out
> otherwise.
>
> It is part of the base install of Ubuntu Server at least since 14.04.
> It came in as a default dependency of udisks on my gentoo systems, which
> is pulled in by a variety of things.  So I assumed it was part of the
> system set.
>
> I like gdisk *way* more than parted.
>
> > GPT has many upgrades over MBR, like duplication at the front/end of the
> > storage, not only at the beginning. Plus not having to deal with
> > "logical/extended" partitions ever again is nice. Wikipdeia has more.
> >
> > Inside a VM, I don't don't use LVM.  Only outside on the hostOS. There
> > are multiple pros/cons to either method. I can understand if folks want
> > LVM inside a VM and why they wouldn't. Do some research.
>
> I do the same.  LVM on bare metal, not in VMs.  All of my VM disks are
> LVs, not files.  Virt-manager makes that easy, btw -- you can make any
> volume group in a host a "pool" for VM allocations.  It was one of the
> final straws that got me off of virtualbox.
>
> > Haven't touched btrfs. Seems there is always some "issue" that is
> > important to me with it. Whether that is true or not is completely
> > irrelevant. It is a hassle that I don't need. Understand many people
> > love btrfs, which is great. More users will eventually fix the issues I
> > have! Thanks!
>
> Yup.  I played with it once.  Haven't touched it since.
>
> > lsblk is nice. Plus, it doesn't need sudo to work (at least not on any
> > systems I manage).
>
> I wrote lsdrv[1] because I didn't like the way lsblk repeated trees when
> raid arrays were present, and I wanted something that would document
> controller ports, device SNs, and UUIDs for later recovery tasks.
> Basically lsblk + blkid + lspci + lsusb in one report.
>
> Phil
>
> [1] https://github.com/pturmel/lsblk
>
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