The blog post Linux I/O scheduler queue size and MyISAM performance explains a good way to increase performance when using Mysql and the Myisam database table engine. I have tried this an can confirm that it will increase performance for this typical application.
I have unfortunately discovered that it may not always increase the overall performance if you have other IO intensive operations besides an Mysql database running on your server. I have a system that runs both Mysql with Myisam and also a custom written database application that uses a lot (like 10000) small files to save data.
The system handles a stream of "messages". I measure performance by looking at graphs of how many messages are buffered (0 to 100000) and how many messages that has been discarded because the buffer is full.
For nr_requests = 128
For nr_requests = 10000
As seen from the graphs the configuration with default nr_requests (128) performs better. My advice is thus to benchmark if your specific application benefits an increased queue size.
16 April 2012
09 April 2012
There are a bunch of ssh clients in Apple App Store that costs money. If your looking for a free one for Ipad the number is reduced: a search for the "ssh" and Price = "Free" yields 9 hits. Out of these 9 only 2 is and actual ssh client: zatelnet and Rove Mobile Admin Client.
Out of curiosity I tried Rove Mobile Admin Client. It's main purpose is actually not to be an ssh client, but to be a remote management tool for their commercial server software. But that doesn't matter, since the ssh client part of the app is free to use standalone. I could successfully connect to my home Linux computer:
Don't expect miracles out of this app, since it is free it is probably a lot worse than some "real" non-free ssh clients. But you can do basic things.
- Can use private key for authentication
- Can edit files in nano (requires rather good terminal emulation and the abilities to send Ctrl sequences).
- Does maintain connection when you switch to another app
- Does not support UTF-8 (since Ubuntu uses this as default it can be a bit frustrating)
- Does not support select, copy and paste in the terminal emulation.
- Very slow (the time for a key press to "echo" is in the magnitude of 1 s).
- Can only have one open connection at a time
A side note: the app also includes an RDP client, but forget about using it, it is painfully slow.