[pve-devel] iscsi, some hang : pvestatd always do iscsi_session_rescan

Alexandre DERUMIER aderumier at odiso.com
Wed May 16 12:05:39 CEST 2012


Hi Dietmar

>>Is a bit difficult to understand, because I do not have that problem. The suggested way 
>>is to use LVM on top of iSCSI, and that avoid the whole problem AFAIK. 

I would like to use lvm but it's not possible in my usage.
I'm use clones/snapshots/remote replication/lun sharing in my san. (each clone=1 lun)

>>Anyways, the whole thing looks like a workaround, and it is maybe easier to fix the cause of the problem (iscsid)? 
>>Form what I see you want: 
>>
>>- do not create any devices at iscsi login 
>>- do not create devices when scanning for luns (any other way to list luns?) 
>>- avtivate/deactivate LUNs selectively 

exactly ! 

(because it's a big change, I wanted to do it in a new separate plugin to not break current model. specially for users with a big number of luns)



>>Because we want to activate/deactivate devices selectively. You already asked the iscsi developers about their opinion? 

Not yet. But adding/remove device is supported by redhat in a clean way.

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/removing_devices.html
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/removing_path-to-storage-device.html
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/adding_storage-device-or-path.html

-Alexandre

----- Mail original ----- 

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Mercredi 16 Mai 2012 06:59:29 
Objet: RE: [pve-devel] iscsi, some hang : pvestatd always do iscsi_session_rescan 

Hi Alexandre, 

> The main advatange with many luns, is that multipath, it's a lot faster as by 
> exemple with 300luns+2 path, I got 600 devices to monitor on each host, and 
> multipathd use a lot of cpu. 
> Also system can be unresponsive in case of iscsi problems with so much 
> devices hanging. 
> And finaly, remove scsi luns if really a pain for the moment, as if you remove 
> a lun in your scan, you need to remove it on each host manually on each 
> path. With this method, device is remove at vm stop :) 
> 
> 
> What do you think about it ? 

Is a bit difficult to understand, because I do not have that problem. The suggested way 
is to use LVM on top of iSCSI, and that avoid the whole problem AFAIK. 

Anyways, the whole thing looks like a workaround, and it is maybe easier to fix the cause of the problem (iscsid)? 
Form what I see you want: 

- do not create any devices at iscsi login 
- do not create devices when scanning for luns (any other way to list luns?) 
- avtivate/deactivate LUNs selectively 

Because we want to activate/deactivate devices selectively. You already asked the iscsi developers about their opinion? 

- Dietmar 



-- 

-- 




	Alexandre D erumier 
Ingénieur Système 
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Fax : 03 20 68 90 81 
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