[Users] iSCSI Storage mirror

[Jaco]

Hi Tal,

Thanks for the reply.

The process I was considering following was something like this:
http://koo.fi/blog/2009/06/10/redundant-iscsi-storage-for-linux/

Write my VM images to a local disk & then use an iSCSI target to 
maintain a copy in the event that the host goes offline, or if I 
otherwise need to do a migration.

I have been looking into GlusterFS (another system I have little 
knowledge or experience of), and I believe that it's more of a 
network-based highly-available & -resilient system than one designed for 
performance. I'm also a little loathe at this late stage of my build to 
introduce more subsystems that'll to be planned for, troubleshooted & 
maintained - I'm not so sure my existing setup will have good support 
for it anyway.
It is certainly something worth-while to consider, but just not at this 
stage (probably v.2 of my deployment).

I hope this answers your questions.

Kind regards

- Jaco

On 13/3/14 5:49 , Tal Nisan wrote:
> As for the oVirt point of view, oVirt does not support storage 
> mirroring out of the box unless it used with Gluster FS
> As for the iSCSI mirroring, what exactly do you mean by mirroring? If 
> you refer to replication then you should probably use Gluster for that 
> matter, if not, can you please send me the actions you are to do 
> manually to try and achieve this mirroring so I can understand better
>
> On 03/09/2013 11:40 PM, Jaco wrote:
>> Hi guys,
>>
>> Got my system (3.2 on CentOS 6.3 - PoC lab v.0.99999) working fairly 
>> OK, with a few issues that's of concern to me.
>>
>> I've now started using iSCSI storage, but kept running into an issue 
>> where the VM's would go into a paused state.
>>
>> A bit of digging in the logs show that it's because of a timeout 
>> issue talking to the iSCSI server/target, which for me raises the 
>> spectre of potential corruption, especially under load.
>> Couldn't understand how this was possible, as I went out & bought 
>> some dedicated hardware to set up a totally separate & isolated 
>> "storage" network, but ended up simply running a cross-over UTP 
>> between the machines (process-of-elimination & all that), but the 
>> issue persisted.
>> This morning I found that one of the mirrored drives started failing, 
>> so (until I've replaced the drive & discovered otherwise) I suspect 
>> that may be the possible cause of the issue.
>>
>> What occurred to me last night, as this thing was keeping me awake, 
>> is that this might not be the *best* course of action, and started 
>> thinking that maybe another way of doing it, especially since oVirt 
>> does some fairly low-level LVM stuff, is to rather store the VM's on 
>> a local drive, get far better IOPS than I could hope for with iSCSI 
>> over GBE, and rather set up the iSCSI to mirror the local device.
>> That way the data is still available on the target in the event a 
>> fail-over/migration needs to take place, but that I'm reducing the 
>> risks a bit while improving overall performance.
>>
>> Is there a way to do this via oVirt, or would I have to do it 
>> manually by setting up storage locally & set up the mirroring via 
>> iSCSI manually as an OS-level?
>> And if so, what would I be looking for & what sort of caveats would I 
>> have to keep in mind in order to make this setup suitable for use by 
>> multiple hosts in the event a (live-)migration needs to take place? 
>> (I'm pretty new at the iSCSI-thing & LVM knowledge is just passable)
>>
>> I'd appreciate anyone's insights into this subject
>>
>> Kind regards
>>
>> - Jaco
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