Re: [Xen-users] Cheap IOMMU hardware and ECC support importance

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 06/24/2014 08:44 PM, Mihail Ivanov wrote:
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> I am looking to use Xen on my workstation and am thinking of 32-64 GB
> ram. Is it really that important to use ECC ram? How often will the
> non-ecc ram crash my system?
If the machine tests as "stable" (a couple of weeks running various 
tests 24/7, including various OCCT tests, and I usually throw in some 
heavily parallel in-ram (on tmpfs) md5sum on large files and sha512sum 
tests on small files (so they fit in the L3 cache) just to be sure - 
probably not very often. But not every memory error will cause a crash 
or even crash a program. It could just silently corrupt a bit of data 
and you may or may not ever find out.
Read the article I sent a link to in reply to your other email and make 
your own mind up.
> Also I've heard about FS corruption and the need to use ZFS.
Yup. Disks die, and when they don't they often lie about their defects. 
And sometimes the errors are silent, rather than a sector read failing 
with an error.
Google for "latent disk errors" for some excellent articles and research 
papers on this subject.
> My machine will not be on 24/7 and I can tolerate
> a restart once per week, but I care a lot about data integrity and my
> file system.
A good start would probably be something like signing up for crashplan 
for backups. Then minimize the chance you'll need it with ECC RAM, ZFS 
and n+2 redundancy.
> I will be running around 10 PV Linux DomU's and some 1-2
> Windows HVM's.(most likely will passthrough a GPU to the one of them).
Depending on the load profile of those domUs you may find you need more 
than 6-8 cores for 12 domUs + dom0.
> I still haven't decided on what hardware should I get.
> Perhaps someone around here with more experience can help.
>
> Things I need:
> IOMMU(fully working one)
> PCI-E slots - 4+(running many Video cards)
Why do you need many GPUs if you said above you are planning to pass a 
(single) GPU to one of your Windows HVMs?
Gordan

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