Study at Cambridge
About the University
Research at Cambridge

IT Services

Department of Engineering

Log in with Raven
  • Home
  • About
    • IT Strategy
  • Services
    • Administrative and information systems
    • Audio-visual facilities
    • Central Computing System
    • Desktop services
    • Network and telephones
    • Printing services
    • Projects and system development
    • Server room facilities for research
    • User accounts and passwords
  • Support
    • IT Helpdesk
    • Computing help web pages
    • Divisional and research support
    • IT Administration
  • News
  • Blogs
  • People
  • Contact us
Home / Blogs / zfs resilver tuning

zfs resilver tuning

May 14, 2015 By John Sloan Leave a Comment

The zfs resilver delay is the amount of time in seconds zfs waits after any zfs io before queing any resilver operations, to avoid degrading performance.

The default on oursystem appears to have the resilver delay as 2.  With that set, it takes 10+days to rebuild a disc when the server is busy with traffic.   With it set to 0, resilvers on dreadnought took about 2 days even when it was fairly heavily used as fileserver – a performance hit to get to a stable system which is probably worthwhile.

On flat VM performance does seem noticeable degraded with it set to 0, so it’s currently set to 1.  This can be tuned back to 0 overnight if needed.

Thankfully it’s a kernel tunable which can be modified on the fly.

 

To read do (on flat/dreadnought/round):

echo zfs_resilver_delay/d | mdb -k

To set do one of:

echo zfs_resilver_delay/w0 | mdb -kw

echo zfs_resilver_delay/w1 | mdb -kw

echo zfs_resilver_delay/w2 | mdb -kw

Leave a Reply Cancel reply

You must be logged in to post a comment.

IT Helpdesk

E-mail: helpdesk@eng.cam.ac.uk
Tel: 32686

  • Helpdesk enquiry form
  • Network connection request form
  • Feedback form

Recent news

AV Upgrades in LT0

September 29, 2016

AV Upgrade in Boardroom

September 1, 2016

AV Upgrades for Lent Term

January 12, 2016

ITX AV Expo 2015

November 3, 2015

LR4 AV System Upgrade

October 21, 2015

More News...

Recent blog posts

PaperCut Popup setup on Mac

October 25, 2017 By Anna Langley

AV Updates- Easter 2017

April 20, 2017 By Gavin MacKenzie

Security Awareness

June 14, 2016 By Caroline Blackmun

IMAP Issue still affects Outlook 2016

November 11, 2015 By Eleanor Blair

iscsi/CHAP notes

September 15, 2015 By John Sloan

More Blog Posts...

Contact

Engineering Department
Trumpington Street
Cambridge CB2 1PZ
United Kingdom (map)
Tel: +44 1223 748203
Fax: +44 1223 332662
E-mail: comp-admin@eng.cam.ac.uk

Information provided by:
webadmin@eng.cam.ac.uk

Privacy policy

Services

  • Administrative and information systems
  • Audio-visual facilities and support
  • Desktop services
  • Network and telephones
  • Linux System
  • Projects and system development
  • Server room facilities for research groups
  • User accounts and passwords

Support

  • IT Helpdesk
  • Computing help web pages
  • Divisional and research support
  • IT administration


© 2014 University of Cambridge

University A-Z
Contact the University
Freedom of information

About the University

How the University and Colleges work
Visiting the University
Maps
News
Jobs
Giving to Cambridge
Global Cambridge