Hi Dominic, If you can't use kernel rbd I think you'll probably have to deal with the higher overhead and lower performance with the tcmu solution. It's possible there might be some things you can tweak at the tcmu layer that will improve things, but when I looked at it there simply seemed to be a lot of extra work being done to do the translation. YMMV. Mark On 10/6/20 12:49 PM, DHilsbos@performair.com wrote:
Mark;
Are you suggesting some other means to configure iSCSI targets with Ceph?
If so, how do configure for non-tcmu?
The iSCSI clients are not RBD aware, and I can't really make them RBD aware.
Thank you,
Dominic L. Hilsbos, MBA Director – Information Technology Perform Air International Inc. DHilsbos@PerformAir.com www.PerformAir.com
-----Original Message----- From: Mark Nelson [mailto:mnelson@redhat.com] Sent: Monday, October 5, 2020 3:40 PM To: ceph-users@ceph.io Subject: [ceph-users] Re: Ceph iSCSI Performance
I don't have super recent results, but we do have some test data from last year looking at kernel rbd, rbd-nbd, rbd+tcmu, fuse, etc:
https://docs.google.com/spreadsheets/d/1oJZ036QDbJQgv2gXts1oKKhMOKXrOI2XLTkv...
Generally speaking going through the tcmu layer was slower than kernel rbd or librbd directly (sometimes by quite a bit!). There was also more client side CPU usage per unit performance as well (which makes sense since there's additional work being done). You may be able to get some of that performance back with more clients as I do remember there being some issues with iodepth and tcmu. The only setup that I remember being slower at the time though was rbd-fuse which I don't think is even really maintained.
Mark
On 10/5/20 4:43 PM, DHilsbos@performair.com wrote:
All;
I've finally gotten around to setting up iSCSI gateways on my primary production cluster, and performance is terrible.
We're talking 1/4 to 1/3 of our current solution.
I see no evidence of network congestion on any involved network link. I see no evidence CPU or memory being a problem on any involved server (MON / OSD / gateway /client).
What can I look at to tune this, preferably on the iSCSI gateways?
Thank you,
Dominic L. Hilsbos, MBA Director - Information Technology Perform Air International, Inc. DHilsbos@PerformAir.com www.PerformAir.com
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