Sunday, December 27, 2015

SDD: TRIM, GC and Greedy Garbage etc

SDD: TRIM, GC and Greedy Garbage etc

It is amazing how we can all look at the same subject but still have a wide range of views. If the discussion is about TRIM and GC then the two should not be confused. That is fair warning, but isn't there something quite obvious in the two different titles? If we extend confusion further what Write Amplification or hot and cold data or SSDs with no TRIM feature at all? The diversity in opinions may well be put down to has:

(a) conducted tests and
(b) which tests were they
(c) any standard involved
(d) any manufacturer spec involved and
(e) any research material read influencing the thought processes?

Who knows the answers as many of the discussions read rarely identify the sources of knowledge.

I cannot guarantee you that this thread will provide all the answers but here are some sources of information that may help. Perhaps you can contribute, too? The materials are not arranged in any particular order.

why-ssd-destroy-court-evidence -

ssd-2014 -

Mac OSx enabling TRIM -

Kingston on Garbage Collection -

On the Optimality of Greedy Garbage Collection for SSDs -

Write Amplification -

A Mean Field Model for a Class of Garbage Collection
Algorithms in Flash-based Solid State Drives

Establishing Professional Guidelines for SSD Forensics: A Case Study -

 Model and Analysis of Trim Commands in Solid State Drives -

To TRIM or Not to TRIM: Judicious TRIMing for Solid State Drives -

DELL Solid State Drive (SSD) FAQ -

SATA-IO Releases Revision 3.1 Specification -

The Fundamental Limit of Flash Random Write Performance: Understanding, Analysis and Performance Modelling -

Performance of garbage collection algorithms for flash-based solid state drives with hot/cold data -

Extending the Lifetime of Flash-based Storage through Reducing Write Amplification from File Systems -

Data Set Management Commands Proposal for ATA8-ACS2 2007 -

Information technology -ATA/ATAPI Command Set - 2 (ACS-2) 2009 -

Information technology -ATA/ATAPI Command Set - 2 (ACS-2) 2011 -

Modelling and Managing SSD Write-amplification -

Sunday, December 20, 2015

Updated: Employment or Computer Forensics Course 2016

There are many people who would like to go into computer forensics that maybe are working elsewhere, currently studying an associated or indirect subject or generally have an interest to find out more. The prospect of employment is naturally the primary objective.

There are many ways to objectify and define a career path. Some look at the academic route first, some the employment route and others take measured assessments to determine the best path forward. It is whatever suits you best because work in civilian careers is different when working with a public sector agency.

1) Interested in working in the public sector - seek out the agency that is of interest to you and find their careers webpage. Now visit other agencies and see if there is a common theme of interest e.g. computer and smartphone forensics, digital investigations etc.

2) Are the qualifications or experience you need for the vacancy and any training offered?

3) Write to an agency to ask for their public statement on recruiting civilian employees in computer forensics?

4) Ask for the link to their public webpage that describes the equal opportunities the public sector agency is lawfully bound to publicise.

What if the private sector is more appealing to you. The above should still stand you in good stead.

Be smart and understand employment advertisements that are simply asking too much e.g. the applicant should be Einstein, know everything, but work for a pittance. These adverts do more harm than good.  Apply a litmus test - (a) what is the time period of experience the person would need to qualify for each subject and then (b) how old does the person need to be.

An example of an employment advertisement seen recently, we looked at the Job description compared with the experience the person would need for each of the subject matters set out in the job description.

A test criteria was identified as to what knowledge skill and experience the applicant would need:

a) read a book,
b) 6mths,
c) 2yrs,
d) 5yrs,
e) 10yrs

Computer Science/Criminal Justice: ........ -v- ..........Time period of experience
- Teach undergraduate and graduate a book, 6mths, 2yrs, 5yrs, 10yrs
- basic and advanced digital forensics and cyber a book, 6mths, 2yrs, 5yrs 10yrs
- Knowledge of digital evidence and a book, 6mths, 2yrs, 5yrs, 10yrs
- network a book, 6mths, 2yrs, 5yrs, 10yrs
- a book, 6mths, 2yrs, 5yrs, 10yrs
- risk a book, 6mths, 2yrs, 5yrs, 10yrs
- information a book, 6mths, 2yrs, 5yrs, 10yrs
- information assurance a book, 6mths, 2yrs, 5yrs 10yrs
- network a book, 6mths, 2yrs, 5yrs, 10yrs
- incident a book, 6mths, 2yrs, 5yrs, 10yrs
- vulnerability a book, 6mths, 2yrs, 5yrs, 10yrs

Given the title of the knowledge, skills and experience sought in the job description realistically a candidate would need to have had maybe between 3yrs-5yrs on each subject. This suggests between 33 to 55 years exposure to dealing with those subjects. So a candidate having started out learning at 20 years of age should be between the age of 53 to 75 to apply for the vacancy?

Alternatively, if only three subjects were the primary requirement then possibly 10 years of knowledge skill and experience might be necessary and the other subjects might be covered by reading a book on each subject.

There are many good employment agencies out there who are sensible and reasonable and define to their clients that given the sum of money they want to pay for the vacancy there needs to be incentives defined for extra knowledge, skills and experience being brought in-house that the company sells as a service to customers as value-added services.  And that is a key-point for potential recruits - what VALUE-ADDED knowledge, skills and experience could you offer above the job description. Never, ever agree to provide every bit knowledge, skills and experience defined in an advertisement.

Absolute goal for research and during interviews:

i) Know the company you want to work for?
ii) Know who are their major competitors?
iii) Seek out the companies market share?
iv) Know whether you can assist maintain their current share or improve on it (e.g. Value Added)?
v) What is the financial status of the company?
vi) Whilst potential employers want to know your life story you equally have the right to know their story, too?
vii) Don't turn down a good job for one thought to be better, only to find out the latter company is using short term government grants to get people off unemployment. Check what is meant by probationary period.

I have updated, as of today (20/12/2015), a list of Universities in England, Wales, Scotland and Ireland offering computer forensic courses for 2016 that are stand alone or incorporated with another subject matter.

These are useful website to find out about the educational qualifications available for computer forensics and related subjects.  I haven't hinted my suggestions about the courses because some fundamental requirements of any forensics discipline is that a person's learns how to:

(1) source information
(2) thoroughly research
(3) identify salient details and facts

University of Bedfordshire

Birmingham City University

Canterbury Christ Church University

Cranfield University

De Montfort University

University of Derby

University of Gloucestershire

University of Greenwich

University of Central Lancashire

Leeds Metropolitan University

Liverpool John Moores University

University of East London

London Metropolitan University

University of London - Royal Holloway

Manchester Metropolitan University

Middlesex University

Northumbria University

The Open University

University of Portsmouth

Sheffield Hallam University

Staffordshire University

University of Sunderland

Teesside University

University of the West of England


Blanchardstown Institute of Technology

University College Dublin

Dublin City University

Letterkenny Institute of Technology

Waterford Institute of Technology


Edinburgh Napier University

University of Glasgow

Glasgow Caledonian University


Cardiff University

University of Glamorgan