Re: [PLUG] Raspbian sqlite project...

[Michael Christopher Robinson]

> Why don't you make the (sensor,timestamp) combination the primary key
> instead?
> 
Makes sense, how do I set the combination (sensor,timestamp) as the
primary key in C code?  Note that I'm using sqlite3.h.
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Re: [PLUG] Raspbian sqlite project...

[Russell Senior]

> "Michael" == Michael Christopher Robinson  
> writes:

Michael> I'm wondering how to count the number of rows in the database
Michael> I'm creating from a C program.  The database has a row number
Michael> or Id that is the primary key.  I need to know how many rows
Michael> there are to know the next row number so I can add more
Michael> temperatures to the database.  I'm developing on a Raspberry Pi
Michael> 3 Model B 2016.  I have six USB temperature sensors hooked up
Michael> that I read from in a loop.  I generate a timestamp using
Michael> time.h and step through the six sensors.  Each sensor has an
Michael> internal temperature and an external temperature.

Michael> Table is like so:

Michael> id, sensor, timestamp, temp_inner, temp_outer.

Michael> With data types:

Michael> Integer, Integer, Integer, float, float.

Michael> If I can't get a row count in the C program, I have to pass it
Michael> in every time I do another round of readings.  I'm using
Michael> sqlite3.h for database access and manipulation.

Michael> I've been trying to answer this question on my own, but finding
Michael> sample C code that does this is not proving to be easy.

Why don't you make the (sensor,timestamp) combination the primary key instead?



-- 
Russell Senior, President
russ...@personaltelco.net
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Re: [PLUG] Multiple hard drive types in SAS raids.

[Tom]

Here is how I look at this...
There are couple of potential issues with mixing different disks and
speeds - 1. reliability 2. economy
1. Reliability - The level of risk depends mainly on whether you are
using software or hardware RAID.
  There is no additional risk for software RAID as long as the disks
work.
  The risk for hardware RAID comes from insufficient testing and not
following your HW RAID controller
  recommendations/spec. Check your RAID card manual and spec - that
should answer the risk level.
  In my somewhat limited experience with couple of hundreds drives -
there is rarely speed/manufacture
  requirement. It is just usual practice in the enterprise, not often
followed by the storage vendors themselves.
2. Economy - mixing fast and slow drive is waste of $$$ for the faster
drives - the RAID is only as fast as its
  slowest component.
Please note that there are other reliability issues to consider beside
mixing different drives and speeds - such as are all the drives
suitable for 24/7 operations, MTTF, max spin up counts, heat, etc.
Perhaps it is one of these monkey's wisdom cases: 
https://www.youtube.com/watch?v=y-PvBo75PDo
Tomas
On Tue, 2017-03-21 at 19:28 -0700, Thomas Groman wrote:
> It has become quite expensive to maintain all the same vendor and
> model
> 15K SAS drives in large raid arrays.
> 
> Would using different vendor SAS drives in the same array cause any
> problems/performance degradation/reliability/ differences?
> 
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Re: [PLUG] Raspbian sqlite project...

[Michael Christopher Robinson]

On Tue, 2017-03-21 at 21:18 -0700, Jonas Augusto wrote:
> Once you have the command line client running you can count the rows
> from a
> table with this query:
> 
> SELECT Count(*) FROM tblName
> 
> Please change the table name at the end (tblName)
> 
> On 21 Mar 2017 21:14, "Jonas Augusto"  wrote:
> 
> You can use the command line client for SQLite: https://www.sqlite.
> org/cli.html
> 
> Once it is connected to your database it is simple to make a SQL
> query. If
> you don't know how the query language works I can help you.
> 
> Jonas

I don't think I want to be doing this manually.  I need to find out the
row count in the C program so I can continue adding temperature data.
This is the program that actually probes the sensors, it needs to do
it's work quietly.  Want to be able to open the database, get the row
count, and continue adding rows to it.  I appreciate the suggestion on
the SQL statement I need, I just need to figure out how to use that
statement in C and what it returns?  I think you get an array back
instead of an int, but there is an int in the array?
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Re: [PLUG] Raspbian sqlite project...

[Jonas Augusto]

Once you have the command line client running you can count the rows from a
table with this query:

SELECT Count(*) FROM tblName

Please change the table name at the end (tblName)

On 21 Mar 2017 21:14, "Jonas Augusto"  wrote:

You can use the command line client for SQLite: https://www.sqlite.
org/cli.html

Once it is connected to your database it is simple to make a SQL query. If
you don't know how the query​ language works I can help you.

Jonas

On 21 Mar 2017 21:03, "Michael Christopher Robinson" <
mich...@robinson-west.com> wrote:

> I'm wondering how to count the number of rows in the database I'm
> creating from a C program.  The database has a row number or Id that
> is the primary key.  I need to know how many rows there are to know the
> next row number so I can add more temperatures to the database.  I'm
> developing on a Raspberry Pi 3 Model B 2016.  I have six USB
> temperature sensors hooked up that I read from in a loop.  I generate a
> timestamp using time.h and step through the six sensors.  Each sensor
> has an internal temperature and an external temperature.
>
> Table is like so:
>
> id, sensor, timestamp, temp_inner, temp_outer.
>
> With data types:
>
> Integer, Integer, Integer, float, float.
>
> If I can't get a row count in the C program, I have to pass it in every
> time I do another round of readings.  I'm using sqlite3.h for database
> access and manipulation.
>
> I've been trying to answer this question on my own, but finding sample
> C code that does this is not proving to be easy.
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Re: [PLUG] Raspbian sqlite project...

[Jonas Augusto]

You can use the command line client for SQLite:
https://www.sqlite.org/cli.html

Once it is connected to your database it is simple to make a SQL query. If
you don't know how the query​ language works I can help you.

Jonas

On 21 Mar 2017 21:03, "Michael Christopher Robinson" <
mich...@robinson-west.com> wrote:

> I'm wondering how to count the number of rows in the database I'm
> creating from a C program.  The database has a row number or Id that
> is the primary key.  I need to know how many rows there are to know the
> next row number so I can add more temperatures to the database.  I'm
> developing on a Raspberry Pi 3 Model B 2016.  I have six USB
> temperature sensors hooked up that I read from in a loop.  I generate a
> timestamp using time.h and step through the six sensors.  Each sensor
> has an internal temperature and an external temperature.
>
> Table is like so:
>
> id, sensor, timestamp, temp_inner, temp_outer.
>
> With data types:
>
> Integer, Integer, Integer, float, float.
>
> If I can't get a row count in the C program, I have to pass it in every
> time I do another round of readings.  I'm using sqlite3.h for database
> access and manipulation.
>
> I've been trying to answer this question on my own, but finding sample
> C code that does this is not proving to be easy.
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[PLUG] Raspbian sqlite project...

[Michael Christopher Robinson]

I'm wondering how to count the number of rows in the database I'm
creating from a C program.  The database has a row number or Id that
is the primary key.  I need to know how many rows there are to know the
next row number so I can add more temperatures to the database.  I'm
developing on a Raspberry Pi 3 Model B 2016.  I have six USB
temperature sensors hooked up that I read from in a loop.  I generate a
timestamp using time.h and step through the six sensors.  Each sensor
has an internal temperature and an external temperature.

Table is like so:

id, sensor, timestamp, temp_inner, temp_outer.

With data types:

Integer, Integer, Integer, float, float.

If I can't get a row count in the C program, I have to pass it in every
time I do another round of readings.  I'm using sqlite3.h for database
access and manipulation.

I've been trying to answer this question on my own, but finding sample
C code that does this is not proving to be easy.
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Re: [PLUG] Multiple hard drive types in SAS raids.

[Russell Senior]

> "Thomas" == Thomas Groman  writes:

Thomas> It has become quite expensive to maintain all the same vendor
Thomas> and model 15K SAS drives in large raid arrays.

Thomas> Would using different vendor SAS drives in the same array cause
Thomas> any problems/performance degradation/reliability/ differences?

I know people who refuse to use the same vendor's drives in a raid
array.  Or at least, never sequential serial numbers!  Systematic
errors--, diversity++!


-- 
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russ...@personaltelco.net
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[PLUG] Multiple hard drive types in SAS raids.

[Thomas Groman]

It has become quite expensive to maintain all the same vendor and model
15K SAS drives in large raid arrays.

Would using different vendor SAS drives in the same array cause any
problems/performance degradation/reliability/ differences?

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Re: [PLUG] two post racks for free

[Thomas Groman]

i might be interested. do you got any photos so i know what i'm lookin at?


On 03/20/2017 09:42 PM, Randall Gray wrote:
> Joe,
> Are these full-height racks?  Have you got anything shorter like the 12U or
> 24U desk-top models?
>
> Thanks!
>
> Randall Gray
>
> On Mon, Mar 20, 2017 at 3:39 PM, Joe Pruett  wrote:
>
>> we have a number of two post racks available if someone wants them. they
>> are disassembled, and i think i can find all the bolts to hold them
>> together, but you might have to make a trip to a hardware store.
>>
>> contact me directly if you're interested. they'll be going to a scrapper
>> soon.
>>
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Re: [PLUG] PLUG Advanced Topics Volunteer?

[Michael Dexter]

On 3/20/17 10:41 AM, Brian P. Martin wrote:
> I heartily second JJJ's sentiment regarding Michael!

Seven years at this? That can't be right.

Thank you Brian!

Michael
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