Postgres Performance - New Connections

Last in the the PostgreSQL Performance series:

Please read more about Test Particulars / Chart Naming methodology from the previous post in the series.

Takeaway:

• New Connection performance has been constant (and at times have mildly deteriorated)
• i.e. Pgbench with -C

• I tried to use all possible combinations to find whether a corner case got better over the releases, but almost every test gave the same result.
• Possibly Tom and others don't consider this a practical use-case and therefore a non-priority.
• Unrelated, in the future, I'd club / write about such tests in a better fashion, rather than posting them as separate posts. I guess I got carried away by the results! Apologies about that.

Postgres Performance - Default Pgbench configurations

Continuing the PostgreSQL Performance series:

Please read more about Test Particulars / Chart Naming methodology from the previous post in the series.

Takeaway:

• Unrelated to the Read-Only performance mentioned earlier, which grew slowly over each Major release, these numbers have grown considerably specifically in 9.5
• 9.5 Branch is at times 35-70% faster than 9.4 Branch
• To reiterate, this test had no Pgbench flags enabled (no Prepared / no Read-Only / etc.) besides 4 Connections & 4 Threads.

Postgres Performance - Read Only

Continuing the PostgreSQL Performance series:

Please read more about Test Particulars / Chart Naming methodology from the previous post in the series.

Takeaway:

• Read-Only Performance numbers have consistently grown from (at least) 9.1 onwards
• 9.5 Branch is 35%-50% faster than 9.1 Branch

Postgres performance - File + ReadOnly

Just wanted to see how Postgres performed when comparing its performance over the different Major releases. I had a spare Pi2 lying around and found it useful for such a performance test.

More inferences to follow, in future posts.
As always, any feedback is more than welcome.

TLDR:

• Despite a regression in 9.3 onwards, the combination of File + Read-Only has improved drastically in the 9.6dev branch
• 9.6dev branch is 
• 2x faster than 9.1 on some tests
• 50% faster than 9.5.2 (currently, the latest stable release!) on some tests
• Yay!!

Hardware:

• Raspberry Pi Model 2B
• 1GB RAM
• 900 MHz Quad-Core-ARM Cortex-A7 (ARMv7 Processor rev 5 (v7l))
• 32GB Class 10 SD Card

Software: Source used for this test

Note:

1. All configurations were run 10 times each
2. All configurations were run for 100 secs each
3. The Phrases in the name of each chart tells what Pgbench was run with:
1. ConnX: with -cX (For e.g. Conn64: with -c64)
2. Thread4: with -j4
3. Prepared: with -M Prepared 
4. File: External SQL file with one SQL command "SELECT 1;"
5. Readonly: with -S
6. 100secs: with -T 100

Using Pi as an home-based Media Server

This is among a series of articles on my experience with the Pi.

This article is about using a Pi as a primitive low-end File-Server for your home network:

Expectations:

• Torrent-Server
• Download Torrents
• Store on a File-Share
• Windows Share
• Serve the File-Share as a Windows Share Drive
• Allow Read / Write to this Windows Share Drive
• Use File-Share as Media-Server
• Using any Smartphone / Laptop
• Play Movies using VLC
• View all Photos / Home-Videos

Effectively:

1. Always on
1. Always accepting new Torrent requests
2. Instantly start downloading 
2. In Real-time
1. Allow user's to view torrent download status
3. Use any UPnP Phone App to play Video content over WiFi on a SmartPhone
4. Use VLC (Network Streaming) to play any Video over WiFi on Laptop / Desktop
5. Use Windows Share Drive and view all Photos / Home-Videos as needed

How-To:

• On Server
• Install Torrent-Daemon
• Configure Torrent-Daemon to listen on RPC requests
• Here's the howto for that
• Configure Samba
• Set the Download folder to be shared
• On Windows
• Install Transmission-GUI-Remote
• Desktop / Smartphone
• Configure GUI to use the RPC based Torrent-Daemon server
• Make this application the default for .torrent & magnet files
• On Linux
• Install Transmission-Remote
• sudo apt-get install transmission-remote
• Configure that to use Daemon (instead of downloading directly with transmission-cli)

Pros/Cons:

• Pros
• Once torrent download has begun, client can disconnect / shutdown client computer
• Server continues to get torrents, after a restart
• miniDLNA serving speed pretty decent
• Watching a movie (over WiFi) on VLC
• CPU ratio barely 0.01 which is pretty decent
• Should be able to easily serve a small army :)
• If no other IO is happening
• If WiFi isn't the bottleneck 
• Cons
• Storage on Pi needs to be managed from time-to-time
• Currently is highly adhoc based
• Truly taking RAID concept to heart!!
• Have 6 Pen Drives (ranging from 4GB to 16GB)
• 8GBs are INR ~170 ( $3 )
• All connected via 3 USB Hubs (both USB 2.0 and USB 3.0)
• One Powered, two non-powered hubs
• Most on Btrfs
• Pretty stable, surprising that still get 1+ MBps with Pi's CPU
• Some VFAT fs since have need of moving stuff off of Pi to a Windows Laptop
• All mounted under /disk
• Very temporary arrangement
• Ideally am looking for a LVM solution (which allows me to remove / add pen-drives on the fly and thus can be called as one) that actually is suited for this purpose.
• But miniDLNA picks up Photo / Audio / Video pretty well from all different mounted folders
• Download speed limitations
• Internet Speed = 2 MBps
• Daemon Download speed capping = 1Mbps
• But PI never reaches it :D !
• Just imagine the poor configuration
• Pi + Btrfs + USB 2.0 + 3 USB Chain + Unpowered Hub
• Still consistent at 450kbps! Impressive!
• Lack of Transmission-Daemon configuration tool means all configuration has to be done via black-screen configuration files
• Careful configuration
• Give all access to 'all' users only if you're sure that all users are going to be careful

Magnifier in Chromebook

Off lately I've started to use the C720 (one of Acer's first Chromebooks) and am I in love with it or what.

While using the Chromebook to view an online Training that was created in a Flash environment (probably using Adobe Connect) I couldn't help myself get frustrated with the fact that I can't do simple things such as Zoom-in on the training video (which happened to be a Shell session) and had to really concentrate on a small part of the screen to read what the font wanted to say.

Most browsers that aren't from the prehistoric era, support zoom-in / zoom-out but the presentation application is 'smart' enough to ensure that that doesn't work as expected. So although the HTML does get enlarged but the presentation stays the same size (just re-centered) to the new zoomed in/out screen space.

A second option (I knew existed in Ubuntu since its early days) had a nifty feature for these situations, where you could just zoom-in and enlarge the screen (unbeknownst to the browser and all applications below the UI layer) this meant that anything rendered on the screen was magnified.

Now Chromebook was smart, pretty compact and an awesome little product, but I really thought expecting graphics related jugglery would be an overkill... and I couldn't find such a feature either.

... Until I read the 'Accessibility' feature in Chromebook (which is a simple little checkbox) and Voila!

Steps:

1. Click User-Image (bottom right)
2. Click Settings
3. Click 'Advanced Settings'
4. Under 'Accessibility' options -> Enable Screen Modifier
5. Zoom-in using .... Ctrl-Alt- button
6. Zoom-out using .... Ctrl-Alt- button

Am still to find things that I can't do on this ultra-cheap / ultra-light / long-lasting-battery / neat laptop!

A Life ... that just happens to have a name.

Zohra Sehgal (1912-2014)

Ae kafir, qadr ki qadr na ho to na sahi,
Ae nadaan, Umr ki fikr na ho to na sahi,

Gar ranjish ho is sadi se ya pichla koi,
To rukh kar, Ja ban ke dikha Zohra koi.