Bug 745655 - Drive Benchmark limitation
Summary: Drive Benchmark limitation
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Fedora
Classification: Fedora
Component: udisks
Version: 16
Hardware: x86_64
OS: Linux
unspecified
low
Target Milestone: ---
Assignee: Tomáš Bžatek
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2011-10-12 22:32 UTC by Thibault Nélis
Modified: 2015-03-03 23:02 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2013-02-13 22:35:22 UTC
Type: ---


Attachments (Terms of Use)
Not-so-useful log (4.67 KB, text/plain)
2011-10-12 22:32 UTC, Thibault Nélis
no flags Details

Description Thibault Nélis 2011-10-12 22:32:09 UTC
Created attachment 527796 [details]
Not-so-useful log

Description of problem:
The benchmark feature of the Disk Utility application seems to randomly crash when measuring the write rate of a relatively small device.

Version-Release number of selected component (if applicable):
1.0.4-1.fc16

How reproducible:
Highly when the volume is "very" small (< ~7G), less when it's bigger.

Steps to Reproduce:
1. Launch Disk Utility (/usr/bin/palimpsest),
2. Start a Read/Write Benchmark on a small drive, or a small RAID array.
  
Actual results:
The software complains that the "helper" exited with an error after trying to write something while there was no space left on the device.

Expected results:
Benchmark ends and the Disk Utility displays the results.

Additional info:
Reading helpers/job-drive-benchmark.c, it seems that measure_write_transfer_rate() can write past the end of the device:

While the size of the device is retrieved correctly, neither the sample size nor the number of samples is adjusted according to it.  Thus, if the size of the device is less than sample_size * num_samples, the program will pick overlapping samples.  While this poses no problem for the first samples, the last ones will "overflow" past the end of the device.

The reason why the results are quite non-deterministic is that the buffer_size (sample_size) *is* adjusted in guesstimate_optimal_buffer_size(), but not according to the size of the device itself:  rather, it is used to measure the read rate of a single sample in order to estimate a sorta optimal buffer_size so that the benchmark doesn't take more than 30 seconds.

This means that in theory, the slower a device is, the less likely it is to hit the bug.  In order to complete the benchmark reliably, the minimum capacity of a device capable of reading at over 666.6MiB/s would be 20000MiB, and less if the device is slower (at least if I got it right).

Solutions include modifying guesstimate_optimal_buffer_size() to adjust the buffer_size according to [device] size or implementing a new guesstimate_optimal_num_samples() routine so that buffer_size * num_samples < size (or a hybrid of those).

Comment 1 Fedora End Of Life 2013-01-16 13:00:49 UTC
This message is a reminder that Fedora 16 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 16. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as WONTFIX if it remains open with a Fedora 
'version' of '16'.

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Comment 2 Fedora Admin XMLRPC Client 2013-02-04 13:43:48 UTC
This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

Comment 3 Fedora End Of Life 2013-02-13 22:35:25 UTC
Fedora 16 changed to end-of-life (EOL) status on 2013-02-12. Fedora 16 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
Fedora please feel free to reopen this bug against that version.

Thank you for reporting this bug and we are sorry it could not be fixed.


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