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Re: [Xen-users] how to start VMs in a particular order

"J. Roeleveld" <joost@xxxxxxxxxxxx> writes:

> On Sunday, June 29, 2014 10:09:32 AM lee wrote:
>> > Quite possibly. Am I correct in assuming you are using old hardware with
>> > closed-source software?
>> It's an IBM x3650 7979 L2G with a ServeRaid 8k.  Arcconf seems to be
>> closed source --- I don't really need arcconf, though.
>> Unfortunately, disabling the status checking hasn't solved the problem.
>> The server goes down with messages about the SCSI bus hanging and trying
>> to reset it.  I suspect that the controller doesn't like the --- rather
>> unsuited --- WD20EARS I plugged in.  They have been working fine with a
>> HP smart array P800, though.  I might have to take them out to see if
>> the problem persists.
> SCSI bus hanging, sounds like an I/O issue.
> Try to read the SMART-values of the disk.

I'm not sure how to do that, and what would they tell me?

> Also, try a different disk...

Unfortunately, I don't have one I could try --- and I'd need three.

> The WD20EARS is a "green" desktop disk. I had numerous issues when using a 
> couple of those in my old server when using software raid (mdadm).
> Some hardware raid cards do not like disks that do not properly return error-
> states. And especially the green disks that have a tendency to go into 
> powersave mode when not used for a short period of time.

I know, they aren't suited for this purpose.  Yet they have been working
fine on the P800, and that three disks should decide to go bad in a way
that blocks the controller (or whatever happens) every now and then
seems unlikely.

So I think it's more likely an incompatibility of these disks with the
ServeRaid controller than the disks being bad, and I'd have to replace
all of them.  Or this controller just sucks.

IBM has supposedly fixed such issues with firmware updates, and
I updated everything I could even before installing the disks.

> The raid-card can easily end up trying to throw that disk out of the
> raid- array. If that is the only disk, that will mean the disk
> suddenly disappeared, causing kernel panics.

It's three in a RAID-5, data only.  There are two small SAS disks in a
RAID-1 for the system.

> I currently use WD Red drives with hardware raid cards.

Yes, I have two of those, 3TB each --- in the desktop on SATA ports now
in software RAID-1 because I need them for backups.  I don't like
backups on hardware raid, and both RAID controllers are limited to
max. 2TB per disk.  The WD reds work fine on the P800, though it only
sees them as 2TB.  I can't put them into the server because I need more
than 2TB.

So there I'm stuck :(  The plan was to have my data on the server.
Perhaps I'll have to declare the experiment as failed and sell the

>> > I use Xen on servers where stability is more important then a fast
>> > boottime. (especially as the BIOS takes longer then booting the OS)
>> Well, I wish the server was running stable!
> See my comment about your disk above. Replace it or connect it directly to 
> the 
> mainboard, bypassing the raid controller.

Afaik, the board doesn't have SATA connectors.  The disks are neatly
contained in an enclosure, through which they are connected to the
available SAS/SATA ports, which are provided via the ServeRaid 8k.
Even if the board had additional SATA ports, I'd have the disks lying
around on top of the case and would need an external power supply for
them, which I don't have.

I could probably run the disks as JBOD.  If they are incompatible with
the controller, that won't help.

Perhaps the controller is broken.  Or it's something that xen does.

>> > All the domUs have their console inside a screen-session. These also log
>> > the output to:
>> > /var/log/xen-consoles/<domu-name>.log
>> > 
>> > By checking if these have the login prompt, you can also ensure the domU
>> > has started correctly. At least the scripts I get with Gentoo cycle when
>> > the screen-session is created.
>> Hmmm ... That is really going to lengths.
> Many roads lead to Rome :)
> Likewise, many ways exist to achieve what you (and I) want. I do not know of 
> an existing tool that does this simply. On a different list, people talk 
> about 
> using puppet or adding additional scripts as dependencies.

I wish it was a feature of xen --- that would make sense, but how would
xen know when a VM is fully up ...

Knowledge is volatile and fluid.  Software is power.

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