Yet Another AoE vs. iSCSI Opinion (YAAVIO)

That’s right, folks! Yet another asshole blogger here, sharing his AoE (ATA over Ethernet) vs. iSCSI (Internet SCSI) opinion with the world!

As if there wasn’t already enough discussion surrounding AoE vs. iSCSI in mailing lists, forums and blogs, I am going to add more baseless opinion to the existing overwhelming heap of information on the subject. I’m sure this will be lost in the noise but after having implemented AoE with CORAID devices and iSCSI with an IBM (well, LSI) device and iSCSI with software targets in the past I feel I finally have something share.

This isn’t a technical analysis. I’m not dissecting the protocols nor am I suggesting implementation of either protocol for your project. What I am doing is sharing some of my experiences and observations simply because I can. Read on, brave souls.

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Migration Weekend: Success

It was a long weekend of watching tape restores and restarting them as necessary but it’s finally over and everything appears to be mostly hunky dory!

I did discovery yet more small misconfigurations and strange behaviour along the way:

  1. OpenLDAP’s syncrepl using “refereshAndPersist” wasn’t working how I expected it to, no new changes were replicating to the slave LDAP server! I changed the directive to “refreshOnly” and set a 10 minute interval. I made several changes and monitored the slave LDAP server. Changes propagated in about 10 minutes, every time.
  2. Despite iSCSI’s maturity and the maturity of QLogic’s HBAs I still noticed strange, unexplained target drop outs. Two HBAs per server, two controllers in the IBM DS3300 and just one target out of four was dropping. At first, I couldn’t figure out how to properly reconnect the target on a live system so I rebooted. Later, I discovered you can “disable” and then “enable” the specific target in SANsurfer or iscli, which worked to bring back the dropped target on a live system. Multipath picked up the “new” path right away, as expected.
  3. Always remember to leave free physical extents in any LVM Volume Group in which you are taking snapshots of the Logical Volumes. It’s freakin’ obvious but I forgot and when I went to do snapshot backups, the snapshots were failing. Now I’m growing some LUNs on the DS3300 so that my VGs have room for snapshots.

All in all, a good weekend that was mostly filled with success.