Hello,
SUMMARY:
I received no replies. The tests I ran did not detect any noticeable
performance hit with quota's enabled for AdvFS (I did not test UFS)
under Digital UNIX 4.0B with patch kit #5. If there is a performance
hit, it appears to be minor. I used fsx for two series of tests; 1.
exercise 5 processes for 5 minutes, 2. exercise 10 processes for 10
minutes. Fsx is a tool supplied with Digital UNIX that creates, opens,
writes, reads, closes, and unlinks files. I have / and /tmp on
separate filesystems and ran the test in /tmp. I ran four tests for
each series with different quota enabled settings; 1. /tmp off, / off,
2. /tmp on / off, 3. /tmp off, / on, 4. /tmp on, / on.
What do the results mean?
1. I picked a bad test.
2. the AdvFS quota enforcement code is very efficient.
3. the AdvFS quota enforcement code is executed regardless of quota
enforcement status.
I don't have the Digital UNIX source to verify when the AdvFS quota
enforcement code is executed.
ORIGINAL POSTING:
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BACKGROUND:
I have a question about quotas that carries on the discussion/summary posted by
atokeni_at_ato.abb.se around 11/3/97.
It was decide that userquota,groupquota should be added to AdvFS filesystems,
via /etc/fstab, to be able to run quotacheck. This is true even for filesystems
that don't need quota enforcement. This fact is also in the DU 4.0 Release
Notes section 4.8.3.18.
Unfortunately, this enables quota enforcement the next time quotaon -a is
invoked, during reboot or manually.
This does not break anything since the default is to allow unlimited quota
by default. However, this mean quota enforcement is now turned on for
undesired filesystems.
QUESTION:
Does quota enforcement add additional overhead to the kernel? Anywhere else?
If it does, then is it worth having quota enforced for all AdvFS filesystems?
If the overhead is noticeable, then perhaps only add the userquota,groupquota
flags to all AdvFS filesystems, run quotacheck, then remove the
userquota,groupquota flags from the filesystems that don't require enforcement.
Of course, this is not an issue for sites with few users. However, we support
over 40,000 user accounts and over 700 concurrent users and growing.
We have AlphaServer 4100, 2100, 2100A, 1000 running either DU 4.0B or 3.2G.
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Regards,
Richard Jackson
Computer Center Lead Engineer
Mgr, Central Systems & Dept. UNIX Consulting
University Computing & Information Systems (UCIS)
George Mason University, Fairfax, Virginia
Received on Tue Nov 11 1997 - 18:44:03 NZDT