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Synology iSCSI NAS becomes innactive with VMware ESXi sessions over time

I have noticed in the past few months as I've been settling my system in (getting everything configured right and all) that my Synology NAS which is hosting an iSCSI volume randomly appears to "disconnect" from certain hosts.  I put that in quotes as the Synology UI still shows the host as connected however the host displays that the SCSI route is dead in the network adapters page and the volume is inactive.  Upon attempting to shut down the NAS I am left with powercycling using a hard boot.  A power cycle of the NAS is the only option as rebooting the host does not reestablish a connection.  Any ideas?
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huntson
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huntson
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1 Solution
 
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
does the host lose contact to the NAS, e.g. network connection?

what does vmkping or ping tell you ?

is your Synology NAS certified for use with ESXi, e.g. on the HCL

we've had lots of bad experiences with Synology NAS, and use only NFS now for Backup, not production, e.g. iSCSI.
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huntsonAuthor Commented:
Not sure how I can answer your question specifically other than telling you it thinks the route is bad. Vmkping shows that the host is seeing the NAS.  

My NAS is certified.  Interesting to hear that considering many people are able to use it successfully.  Any advice for troubleshooting as it only appears to be happening on this one NAS (i have several).  I was thinking about migrating everything off and recreating the disk.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
if you have networking issues, constant vmkpings and pings, and look at VMware ESXi logs /var/logs

check networking.

is this only one LUN which is causing issues, any other LUNs present ?

do you have jumbo frames enabled ?

are you using multipath ?
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huntsonAuthor Commented:
What is the best way to do an indefinite ping?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
vmkping is better because you can specify a vmkernel portgroup to send the "iSCSI data packet"
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huntsonAuthor Commented:
How do I keep that going with vmkping?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
-c

followed by a number for packet count.

e.g.

-c 1024

Open in new window

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huntsonAuthor Commented:
FYI this is exactly my issue - not sure if it'll get solved without downgrading:

https://forum.synology.com/enu/viewtopic.php?f=147&t=116743&start=180
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
again compatibility issue!

don't use iSCSI!
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huntsonAuthor Commented:
I see where you're coming from but I loose some compatibility and ability to do certain things if I do it all as NFS - don't I?

Apparently the solution was to add


iscsi_cmd_defer_exec="0"


at the end of

/etc.defaults/synoinfo.conf


Do this by telneting in and elevating to sudo.  I also changed the max SCSI connections to 256 in the advanced settings of my client as this was a suggestion for my issue however I'm not sure if that's have any impact
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
What do you lose if you use NFS ?

NFS has less overhead on the NAS, because it's designed around NFS, iSCSI adds additional layer, and CPU overhead, Synology processors are not that fast, and they do not have dedicated storage processors!
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huntsonAuthor Commented:
So I can migrate and do all that fun stuff just like iSCSI?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
VMware vSphere ESXi supports NFS.

If you've not tried NFS and Jumbo Frames, you may find a performance increase.

It's worth trying...(less overhead).
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huntsonAuthor Commented:
I emailed tech support and found the solution.
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