Bu Blogda Ara

15 Kasım 2011 Salı

10 Ekim 2011 Pazartesi

Open source software for building private and public clouds

Worth looking at. Led by very strong companies, collobration is high and license is Apache!

29 Haziran 2011 Çarşamba

2 Haziran 2011 Perşembe

Information about Red-Hat 32-bit kernels from Memory Management Perspective

Until today Red-Hat had support for 3 types of kernels no-smp,, smp (pae) and hugemem kernels. Of these 3 kernels hugemem kernel was released for Red-Hat 3 and 4 versions but dropped after that. I will explain the reason I found for that below but first of all lets try to understand the need for hugemem kernel. Lets look at the limitations of kernels:

NO-SMP kernels, memory space usage
* Generally 16MB DMA, 896MB low memory and rest is high memory.
* Max supported phy. memory is 4GB

1.0 GB Text/code
1.7 GB available process memory for mmap, malloc / address space
(e.g. usable by shared Pool)
0.3 GB Stack
1.0 GB Kernel space (all low memory + some portion of high memory)

SMP kernels, memory space usage is same as NO-SMP except that the total mem is increased upto

* Still 16MB DMA, 896MB low memory and rest is high memory.
* Max supported phy. memory is 64GB. Although 16GB is recommended; this is because kernel-space should know and hold reference for user-space resources and because of this when user-space usage increases over 16GB the kernel space's starts to consume all the low memory part thus OOM killer tries to kill user-space processes to free up space in the kernel space and the system can fall into a hang state finally.
* CPU's address extension and kernels pae support together provide more User space for the processes but kernel space and memory space partitioning

1.0 GB Text/code
1.7 GB available process memory for mmap, malloc / address space
(e.g. usable by shared Pool)
0.3 GB Stack
1.0 GB Kernel space

Hugemem kernels, memory space usage
* It is memtioned that low memory configuration changed but I could not find a definite number yet. As far as the kernel space increased upto 4GB 4 times larger than before low memory should also have been increased. If I can find a hugemem kernel installed I will cat /proc/meminfo
* Hugemem kernel support was introduced in RedHat 3-4 but droped later. This is because highmem patches were never accepted upstream. The guys in the Red Hat team assumed that 64bit architecture is wide spreading and the hugemem effort to cure the 32+4 bit architecture sickness should not be carried on.

1.0 GB Text/code
2.7 GB available process memory for mmap, malloc / address
space (e.g. usable by shared Pool)
0.3 GB Stack
4.0 GB Kernel

So if you take a look at the official Red Hat Enterprise Linux Technology capabilities and limits page you will see that max phy memory support drops 16GB from 64GB for Redhat 5 and later on 32-bit architecture. You should remember that 64GB still possible for SMP PAE kernel but dangerous for consuming kernel resources and bringing the system in a hang state.

Remember that 64-bit arch treats all memory as low memory and memory limit is theoretically upto 8TB and practically 250GB-1TB for linux kernels. And I think its important to align the development strategies for 32-bit or 64-bit with RedHat teams strategic decisions; if you are developing software for this platform.

9 Mayıs 2011 Pazartesi

rsync with ssh for resumable scp behaviour

Dont you get annoyed when you have a fragile vpn or internet connection to a site where you are trying to download a large file via scp and the transfer is broken on the half way or even when you are about to finish %99 lol.

So this happened to me these days so I discovered rsync with ssh option to continue downloading from where just the download was interrupted.

sudo rsync --partial --progress --rsh=ssh username@ipaddress:/path_to_file /path_to_target_folder

If you have a different port than default ssh port

sudo rsync --partial --progress --rsh='ssh -p12321' username@ipaddress:/path_to_file /path_to_target_folder

Note: This also works after when scp transfer was broken. You still continue to download from where you remained.

18 Nisan 2011 Pazartesi

How to extend a Virtual Box Image Hard Disk Size

1-) Use clonezilla latest.iso and boot from Virtual Machine the iso.

2-) Copy the source disk to target disk with Expert mode and k1 mode selected which is for scaling up the existing virtual disk to target virtual disk.

3-) When finished open the virtual machine with a latest gparted.iso image.

4-) Enter the commmand line mode and pvscan the virtual hard disk and Note your virtual harddisk path such as /dev/sda2

5-) sudo pvresize /dev/sda2 This is done for resizing the outer LVM2 type Virtual Disk partition.

6-) lvscan to discover internally mapped virtual ext3 or ext2 linux partitions such as /dev/mapper/virtual-disk-name

7-) sudo lvresize -L /dev/mapper/virtual-disk-name This will extend your inner mapped linux partition.

8-) resize2fs /dev/mapper/virtual-disk-name This will resize the filesystem.

5 Mart 2011 Cumartesi

Graph Visualization tool for Ant makefiles.

I recommend Grand as a graph visualization tool for Ant files.

17 Ocak 2011 Pazartesi

Tips for installing memcached on Red-Hat 4

1-) web access :)

2-) rpm -ihv ftp://ftp.pbone.net/mirror/ftp.pramberger.at/systems/linux/contrib/rhel4/archive/x86_64/libevent-1.3e-4.el4.pp.i386.rpm

3-) rpm -ihv htp://ftp.pbone.net/mirror/ftp.pramberger.at/systems/linux/contrib/rhel4/archive/i386/memcached-1.4.5-1.el4.pp.i386.rpm

Dont install memcached 1.2 versio0n and the stupid libevent 1.3b beta release than you will get EAGAIN resource temporyliy unavailable erro when trying to asyncroushly write to memcached server.

11 Ocak 2011 Salı

Our Coreopsis Rota Video Monitoring Deprecated Latest release

We stopped developing the Coreopsis Project on 2007. This is the latest release of our Windows Based Ip Camera management system (2007). From the below link download Setup1_05.zip. Only Windows XP Windows 2000 and Windows 2003 servers are supported. The software is for free....