SES Planing: keeping ISCSI gates on OSD nodes - is wise?

Thinking about how to deploy SES for block-oriented applications “in smart way”, I made a conclusion the iSCSI gateways should be deployed at the same servers with OSD nodes.

Pro:

  • The “locality” of the iSCSI gate and corresponding image container might increase the productivity by removing LAN infrastructure from “local” data path.
  • If the cluster is not tweaked, the possibility of local data hit is 1 / OSD_Number. Thus, the smaller the cluster, the greater the gain.
  • If the CRUSH map will be tweaked to store more container data locally to their iSCSI gates, the gain will be increased.
  • The iSCSI multipathing might increase the performance as well.
  • If the CPU will be saturated, the classic Hi-End approach “one role per node” still might be used.

Contra:

  • The amount of administrative work is increased.
  • Will SUSE still support such non-standard configuration? For example, 3 nodes for monitors and 10 nodes for OSD+iSCSI…

Am I right?

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Still seems the idea is good. Here is the example of lrbd configuration file, which allows to serve single iSCSI target with 4-way multipathing to 4 OSD nodes.

{ "auth": [ { "target": "iqn.2016-07.org.ses-iscsi.igw.x86:mpath", "authentication": "none" } ], "targets": [ { "target": "iqn.2016-07.org.ses-iscsi.igw.x86:mpath", "hosts": [ { "host": "osd01", "portal": "portal01" }, { "host": "osd02", "portal": "portal02" }, { "host": "osd03", "portal": "portal03" }, { "host": "osd04", "portal": "portal04" } ] } ], "portals": [ { "name": "portal01", "addresses": [ "172.18.65.144" ] }, { "name": "portal02", "addresses": [ "172.18.65.153" ] }, { "name": "portal03", "addresses": [ "172.18.65.154" ] }, { "name": "portal04", "addresses": [ "172.18.65.155" ] } ], "pools": [ { "pool": "iscsi01", "gateways": [ { "target": "iqn.2016-07.org.ses-iscsi.igw.x86:mpath", "tpg": [ { "image": "iscsivol01" } ] } ] } ] }