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



polezhaevdmi
18-Jul-2016, 10:25
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?

Automatic Reply
25-Jul-2016, 05:30
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polezhaevdmi
26-Jul-2016, 14:45
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" } ]
}
]
}
]
}