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Feature #1437

COMSTAR only supports 255 targets

Added by Alasdair Lumsden almost 8 years ago. Updated over 3 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
comstar - iSCSI/FC/SAS target
Start date:
2011-08-31
Due date:
% Done:

0%

Estimated time:
Difficulty:
Medium
Tags:
needs-triage

Description

255 targets ought to be enough for anybody, right? Well, perhaps not :-)

In cloud environments with a lot of guests where you're doing a 1:1 mapping between target and guest, you can quickly hit the 255 limit. We (EveryCity) just did. :-/

We knew this day would come but didn't think we'd hit it so soon, and now we have a SAN which has vastly more storage than we can utilise.

I'm not sure how difficult/easy this would be to up, but it might be useful for Nexenta who no doubt have customers who would like > 255 targets.


Related issues

Has duplicate illumos gate - Feature #3694: RFE: itadm increase the number of targets to 512 or 1024Closed2013-04-04

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History

#1

Updated by Alasdair Lumsden almost 8 years ago

Someone pointed out:

http://src.illumos.org/source/xref/illumos-gate/usr/src/lib/libiscsit/common/libiscsit.h#40

Which has:

#define MAX_TARGETS 255 /* maximum targets that may be created */

I'm no kernel developer but it looks like the targets are stored in a linked list with a 32bit unsigned integer storing the count, so potentially the real maximum is 4bn?

crsd on IRC recompiled libiscsit.so.1 and tested creating more targets and nothing exploded immediately:

23:53 < crsd> AlasAway: http://pastebin.com/9ykAcD62 (not sure if it really works though :-)

#2

Updated by George-Cristian Bîrzan almost 6 years ago

I'd like to weigh in and say that we've been running several machines in production for months with as many as 500 targets, with no visible side effects.

#3

Updated by Yuri Pankov over 3 years ago

Looking at the code, I don't see why we have that limit at all - may be we could just remove it instead of increasing?

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