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Feature #1437

open

COMSTAR only supports 255 targets

Added by Alasdair Lumsden about 10 years ago. Updated over 5 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
Gerrit CR:

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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Actions #1

Updated by Alasdair Lumsden about 10 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 :-)

Actions #2

Updated by George-Cristian Bîrzan about 8 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.

Actions #3

Updated by Yuri Pankov over 5 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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