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From Koushik Das <koushik....@accelerite.com>
Subject Re: Attaching more than 14 data volumes to an instance
Date Thu, 16 Feb 2017 05:36:01 GMT
The hardcoded value of 15 needs to be fixed, it can be replaced with getMaxDataVolumesSupported()
just above it. Please file a bug and if possible raise a PR as well.

-Koushik

On 15/02/17, 11:21 PM, "Voloshanenko Igor" <igor.voloshanenko@gmail.com> wrote:

    On VM we try to emulate real hardware )))
    So any device honor specification
    In this case PCI :)
    
    To be honest we can increase limits by adding multifunctional devices or
    migrate to virtio-iscsi-blk
    
    But as for me - 14 disks more than enough now
    
    
    About 3 for cdrom. I will check . I think CDROM emulated as IDE device, not
    via virtio-blk
    
    For 0 - root volume , interesting , in this case we can easily add 1 more
    DATA disk :)
    
    ср, 15 февр. 2017 г. в 19:24, Rafael Weingärtner <
    rafaelweingartner@gmail.com>:
    
    > I thought that on a VM we would not be bound by PCI limitations.
    > Interesting explanations, thanks.
    >
    >
    > On Wed, Feb 15, 2017 at 12:19 PM, Voloshanenko Igor <
    > igor.voloshanenko@gmail.com> wrote:
    >
    > > I think explanation very easy.
    > > PCI itself can handle up to 32 devices.
    > >
    > > If you run lspci inside empty (fresh created) VM - you will see, that 8
    > > slots already occupied
    > > [root@test-virtio-blk ~]# lspci
    > > 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev
    > > 02)
    > > 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton
    > II]
    > > 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton
    > > II]
    > > 00:01.2 USB controller: Intel Corporation 82371SB PIIX3 USB
    > [Natoma/Triton
    > > II] (rev 01)
    > > 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
    > > 00:02.0 VGA compatible controller: Cirrus Logic GD 5446
    > > 00:03.0 Ethernet controller: Red Hat, Inc Virtio network device
    > > 00:04.0 SCSI storage controller: Red Hat, Inc Virtio block device
    > >
    > > [root@test-virtio-blk ~]# lspci | wc -l
    > > 8
    > >
    > > So, 7 system devices + 1 ROOT disk
    > >
    > > in current implementation, we used virtio-blk, which can handle only 1
    > > device per instance.
    > >
    > > So, we have 32-8 == 24 free slots...
    > >
    > > As Cloudstack support more than 1 eth cards - 8 of them reserved for
    > > network cards and 16 available for virtio-blk
    > >
    > > So, practical limit equal 16 devices (for DATA disks)
    > >
    > > Why 2 devices (0 + 3) excluded - interesting question... I will try to
    > > research and post explanation
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > > 2017-02-15 18:27 GMT+02:00 Rafael Weingärtner <
    > rafaelweingartner@gmail.com
    > > >:
    > >
    > > > I hate to say this, but probably no one knows why.
    > > > I looked at the history and this method has always being like this.
    > > >
    > > > The device ID 3 seems to be something reserved, probably for Xen tools
    > > (big
    > > > guess here)?
    > > >
    > > > Also, regarding the limit; I could speculate two explanations for the
    > > > limit. A developer did not get the full specs and decided to do
    > whatever
    > > > he/she wanted. Or, maybe, at the time of coding (long, long time ago)
    > > there
    > > > was a hypervisor that limited (maybe still limits) the number of
    > devices
    > > > that could be plugged to a VM and the first developers decided to level
    > > > everything by that spec.
    > > >
    > > > It may be worth checking with KVM, XenServer, Hyper-V, and VMware if
    > they
    > > > have such limitation on disks that can be attached to a VM. If they do
    > > not
    > > > have, we could remove that, or at least externalize the limit in a
    > > > parameter.
    > > >
    > > > On Wed, Feb 15, 2017 at 5:54 AM, Friðvin Logi Oddbjörnsson <
    > > > fridvin@greenqloud.com> wrote:
    > > >
    > > > > CloudStack is currently limiting the number of data volumes, that
can
    > > be
    > > > > attached to an instance, to 14.
    > > > > More specifically, this limitation relates to the device ids that
    > > > > CloudStack considers valid for data volumes.
    > > > > In method VolumeApiServiceImpl.getDeviceId(long, Long), only device
    > > ids
    > > > 1,
    > > > > 2, and 4-15 are considered valid.
    > > > > What I would like to know is: is there a reason for this limitation?
    > > (of
    > > > > not going higher than device id 15)
    > > > >
    > > > > Note that the current number of attached data volumes is already
    > being
    > > > > checked against the maximum number of data volumes per instance, as
    > > > > specified by the relevant hypervisor’s capabilities.
    > > > > E.g. if the relevant hypervisor’s capabilities specify that it only
    > > > > supports 6 data volumes per instance, CloudStack rejects attaching
a
    > > > > seventh data volume.
    > > > >
    > > > >
    > > > > Friðvin Logi Oddbjörnsson
    > > > >
    > > > > Senior Developer
    > > > >
    > > > > Tel: (+354) 415 0200 | fridvin@greenqloud.com <
    > jaroslav@greenqloud.com
    > > >
    > > > >
    > > > > Mobile: (+354) 696 6528 | PGP Key: 57CA1B00
    > > > > <https://sks-keyservers.net/pks/lookup?op=vindex&search=
    > > > > fridvin@greenqloud.com>
    > > > >
    > > > > Twitter: @greenqloud <https://twitter.com/greenqloud> | @qstackcloud
    > > > > <https://twitter.com/qstackcloud>
    > > > >
    > > > > www.greenqloud.com | www.qstack.com
    > > > >
    > > > > [image: qstack_blue_landscape_byqreenqloud-01.png]
    > > > >
    > > >
    > > >
    > > >
    > > > --
    > > > Rafael Weingärtner
    > > >
    > >
    >
    >
    >
    > --
    > Rafael Weingärtner
    >
    




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