[Users] iSCSI Storage mirror
Jaco
ubuntumuntu at gmail.com
Wed Mar 13 18:36:26 UTC 2013
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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