Hi all, I''m just curios and would like some input from the community on this one. We''re busy budgeting for a couple of new servers and I thought it would be good to try out the Core i7 CPU''s, but see the majority of them don''t offer VT-d, but just VT-x. Looking at the LGA1366 range, only the "Intel lga1366 i7 980XE" (from the list of what our suppliers stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could purchase 4 more CPU''s, which could translate to 40x - 80x more VM''s being hosted for the same capital outlay. Experience has shown that we under-utilize CPU''s by a great margin and memory / HDD IO is our biggest bottleneck on any server. So, if VT-d really necessary? We mainly host XEN virtual machine for the hosting industry, i.e. we don''t need / use graphics rendering inside VM''s, or need DAS on the VM''s, etc. -- Kind Regards Rudi Ahlers SoftDux Website: http://www.SoftDux.com Technical Blog: http://Blog.SoftDux.com Office: 087 805 9573 Cell: 082 554 7532 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Juergen Gotteswinter
2010-Sep-15 09:49 UTC
Re: [Xen-users] is Intel VT-d "really" necessary?
No, if you dont want to use unmodified os or windows vt doesnt really matter... On 09/15/2010 11:20 AM, Rudi Ahlers wrote:> Hi all, > > I''m just curios and would like some input from the community on this > one. We''re busy budgeting for a couple of new servers and I thought it > would be good to try out the Core i7 CPU''s, but see the majority of > them don''t offer VT-d, but just VT-x. Looking at the LGA1366 range, > only the "Intel lga1366 i7 980XE" (from the list of what our suppliers > stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or > 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could > purchase 4 more CPU''s, which could translate to 40x - 80x more VM''s > being hosted for the same capital outlay. Experience has shown that we > under-utilize CPU''s by a great margin and memory / HDD IO is our > biggest bottleneck on any server. > > So, if VT-d really necessary? > We mainly host XEN virtual machine for the hosting industry, i.e. we > don''t need / use graphics rendering inside VM''s, or need DAS on the > VM''s, etc. >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Even then, I believe VT-d is for PCI pasthrough, which you say you don''t need even if you do want to run unmodified OSes. Dustin -----Original Message----- From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Juergen Gotteswinter Sent: Wednesday, September 15, 2010 05:50 To: xen-users Subject: Re: [Xen-users] is Intel VT-d "really" necessary? No, if you dont want to use unmodified os or windows vt doesnt really matter... On 09/15/2010 11:20 AM, Rudi Ahlers wrote:> Hi all, > > I''m just curios and would like some input from the community on this > one. We''re busy budgeting for a couple of new servers and I thought it > would be good to try out the Core i7 CPU''s, but see the majority of > them don''t offer VT-d, but just VT-x. Looking at the LGA1366 range, > only the "Intel lga1366 i7 980XE" (from the list of what our suppliers > stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or > 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could > purchase 4 more CPU''s, which could translate to 40x - 80x more VM''s > being hosted for the same capital outlay. Experience has shown that we > under-utilize CPU''s by a great margin and memory / HDD IO is our > biggest bottleneck on any server. > > So, if VT-d really necessary? > We mainly host XEN virtual machine for the hosting industry, i.e. we > don''t need / use graphics rendering inside VM''s, or need DAS on the > VM''s, etc. >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
>>> On 2010/09/15 at 03:20, Rudi Ahlers <Rudi@SoftDux.com> wrote: > Hi all, > > I''m just curios and would like some input from the community on this > one. We''re busy budgeting for a couple of new servers and I thought it > would be good to try out the Core i7 CPU''s, but see the majority of > them don''t offer VT-d, but just VT-x. Looking at the LGA1366 range, > only the "Intel lga1366 i7 980XE" (from the list of what our suppliers > stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or > 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could > purchase 4 more CPU''s, which could translate to 40x - 80x more VM''s > being hosted for the same capital outlay. Experience has shown that we > under-utilize CPU''s by a great margin and memory / HDD IO is our > biggest bottleneck on any server.That''s interesting...is it the motherboards you''re seeing this lack of support on, or the chips? I''m pretty sure the i7 processors themselves support VTd, you just have to have the BIOS and MB support for it.> > So, if VT-d really necessary? > We mainly host XEN virtual machine for the hosting industry, i.e. we > don''t need / use graphics rendering inside VM''s, or need DAS on the > VM''s, etc.In an environment where you''re planning on running many VMs on a single host, I don''t imagine VTd is going to be very helpful to you. I use it here where I work, but I use it on desktop systems where folks need access to graphics cards, serial cards, etc., from Windows, and not on my server systems. It really depends on what you''re doing as to whether you think you''ll need it or not - if you cannot think of a situation where *any* type of PCI card needs to be forwarded through to an HVM domU, then you''re probably okay without it. The few situations I can think of are: - Serial port cards, but this is really more common on desktops - Phone/Voicemail systems - If you''re using any sort of telephony card with an HVM domU you''ll need direct PCI access, which requires VTd. - Other, vendor-specific add-in PCI cards, for applications like industrial automation, etc. But you won''t see much of this in a data center. Also, keep in mind that, IIRC, PV domUs can access PCI devices without VTd, so if you''re going to be running PV kernels on these systems, or the PV kernels you''re running are the ones that need access to the PCI devices, then you''re probably fine without it. I''m sure it offers some performance enhancements over software-based IOMMU, but I don''t know what those are. -Nick -------- This e-mail may contain confidential and privileged material for the sole use of the intended recipient. If this email is not intended for you, or you are not responsible for the delivery of this message to the intended recipient, please note that this message may contain SEAKR Engineering (SEAKR) Privileged/Proprietary Information. In such a case, you are strictly prohibited from downloading, photocopying, distributing or otherwise using this message, its contents or attachments in any way. If you have received this message in error, please notify us immediately by replying to this e-mail and delete the message from your mailbox. Information contained in this message that does not relate to the business of SEAKR is neither endorsed by nor attributable to SEAKR. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Wed, Sep 15, 2010 at 7:38 AM, Nick Couchman <Nick.Couchman@seakr.com> wrote:>>>> On 2010/09/15 at 03:20, Rudi Ahlers <Rudi@SoftDux.com> wrote: >> Hi all, >> >> I''m just curios and would like some input from the community on this >> one. We''re busy budgeting for a couple of new servers and I thought it >> would be good to try out the Core i7 CPU''s, but see the majority of >> them don''t offer VT-d, but just VT-x. Looking at the LGA1366 range, >> only the "Intel lga1366 i7 980XE" (from the list of what our suppliers >> stock) have VT-d, and it costs 4x more than "Intel lga1366 i7 930" or >> 2x more than "Intel lga1366 i7 960". From a budget perspecitve I could >> purchase 4 more CPU''s, which could translate to 40x - 80x more VM''s >> being hosted for the same capital outlay. Experience has shown that we >> under-utilize CPU''s by a great margin and memory / HDD IO is our >> biggest bottleneck on any server. > > That''s interesting...is it the motherboards you''re seeing this lack of support on, or the chips? I''m pretty sure the i7 processors themselves support VTd, you just have to have the BIOS and MB support for it. > >> >> So, if VT-d really necessary? >> We mainly host XEN virtual machine for the hosting industry, i.e. we >> don''t need / use graphics rendering inside VM''s, or need DAS on the >> VM''s, etc. > > In an environment where you''re planning on running many VMs on a single host, I don''t imagine VTd is going to be very helpful to you. I use it here where I work, but I use it on desktop systems where folks need access to graphics cards, serial cards, etc., from Windows, and not on my server systems. It really depends on what you''re doing as to whether you think you''ll need it or not - if you cannot think of a situation where *any* type of PCI card needs to be forwarded through to an HVM domU, then you''re probably okay without it. The few situations I can think of are: > - Serial port cards, but this is really more common on desktops > - Phone/Voicemail systems - If you''re using any sort of telephony card with an HVM domU you''ll need direct PCI access, which requires VTd. > - Other, vendor-specific add-in PCI cards, for applications like industrial automation, etc. But you won''t see much of this in a data center. > > Also, keep in mind that, IIRC, PV domUs can access PCI devices without VTd, so if you''re going to be running PV kernels on these systems, or the PV kernels you''re running are the ones that need access to the PCI devices, then you''re probably fine without it. I''m sure it offers some performance enhancements over software-based IOMMU, but I don''t know what those are. > > -Nick >Apologies in advance for hyjacking your thread, but this is an interesting question. For cases where PCI passthougth is the heart of the application, is it better to use hvm/VTd or pv-ops/iommu=soft? Or is there some other combination where you can still leverage VTd from pv-ops? -Bruce> > > -------- > This e-mail may contain confidential and privileged material for the sole use of the intended recipient. If this email is not intended for you, or you are not responsible for the delivery of this message to the intended recipient, please note that this message may contain SEAKR Engineering (SEAKR) Privileged/Proprietary Information. In such a case, you are strictly prohibited from downloading, photocopying, distributing or otherwise using this message, its contents or attachments in any way. If you have received this message in error, please notify us immediately by replying to this e-mail and delete the message from your mailbox. Information contained in this message that does not relate to the business of SEAKR is neither endorsed by nor attributable to SEAKR. > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > Apologies in advance for hyjacking your thread, but this is an > interesting question. > > For cases where PCI passthougth is the heart of the application, is it > better to use hvm/VTd or pv-ops/iommu=soft? Or is there some other > combination where you can still leverage VTd from pv-ops? >I believe that PV (pv-ops) can still leverage VTd, and will, by default, if it''s present. If it''s not present, you have to use iommu=soft. -Nick -------- This e-mail may contain confidential and privileged material for the sole use of the intended recipient. If this email is not intended for you, or you are not responsible for the delivery of this message to the intended recipient, please note that this message may contain SEAKR Engineering (SEAKR) Privileged/Proprietary Information. In such a case, you are strictly prohibited from downloading, photocopying, distributing or otherwise using this message, its contents or attachments in any way. If you have received this message in error, please notify us immediately by replying to this e-mail and delete the message from your mailbox. Information contained in this message that does not relate to the business of SEAKR is neither endorsed by nor attributable to SEAKR. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users