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Ubuntu 16.10 forced me to migrate iSCSI targets to openscsi as previous package iscsitarget (also known as ietd - iSCSI Enterprise Target Daemon) was unsupported and removed.

Open-iscsi works, and the only thing I am missing is how to control target-side disk cache?

Previously I was setting IOMode=wb in ietd.conf. How can I achieve the same effect in open-iSCSI targets?

Target-side writeback cache is required to avoid extremely significant write speed degradation on RAID-6 arrays (500mb/sec -> 100mb/sec). If you commit every SCSI command to disk - you'll be updating parity all the time and your speed will be limited to 1 disk. Client-side write cache does not help with this problem.

BarsMonster
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1 Answers1

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I can't test on my laptop but,

NOTE: IOMode "wb" is ignored when employing blockio as it performs no caching.

WARNING: IOMode=wb could lead to serious data loss from an unexpected system failure (power loss, system crash). Use at your own risk!

If you are using blockio switch to fileio as this link documents:

WinEunuuchs2Unix
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  • Unfortunately, ietd is no longer in Ubuntu and was replaced by open-iscsi since 17.10. This is exactly how this issue started. – BarsMonster Feb 13 '19 at 01:28
  • It is in 12.04, 14.04, 16.04, 17.10, 18.04 and 18.10 according to link: http://manpages.ubuntu.com/manpages/xenial/en/man5/ietd.conf.5.html – WinEunuuchs2Unix Feb 13 '19 at 01:31
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    E: Unfortunately when you click any other versions - it redirects back to 16.04... Also tried it on 17.10: E: Package 'iscsitarget' has no installation candidate – BarsMonster Feb 13 '19 at 01:34
  • Darn that is sneaky! Since 16.10 died an EOL (End of Life) two years ago have you thought about switching to 16.04 which has at least two years of life left? Hopefully by then the package will be upgraded to 18.04, 20.04 or 21.04? IIRC there were many packages not upgraded when 18.04 was rushed to market. – WinEunuuchs2Unix Feb 13 '19 at 01:43
  • The official position of Ubuntu maintainers is that iscsitarget package is not maintained and is abandoned. It's repository was not updated for 9 years, so I doubt it will ever live again. – BarsMonster Feb 13 '19 at 01:47
  • Hmmm.... I'll do some more digging tomorrow and hopefully someone else does too! – WinEunuuchs2Unix Feb 13 '19 at 02:14