Daz's bits and bobs …bytes bits
I’m using the following crontab script to renice my squid process….
Put following in script and call via cron (i’m doing every 10 mins)
*/10 * * * * /home/user/renice.sh
(renice.sh)
renice -15 $(ps -C squid3 -o pid=)
renice -15 $(ps -C unlinkd -o pid=)
I hit this as a problem recently. One of my disks died in my raidz so i ran down to the store and grabbed me a replacement WD10EARS (Western Digital 1Tb Green) drive.
BUT…
The one thing the store didn’t mention to me is the new 4K cluster sizing on the drive. I guess they assume most people run windows (though the issues are also present in XP). See these posts…
http://blog.temeletry.co.uk/2010/05/wd-green-wd10ears/
Unfortunately they really don’t work as well as you’d like in a server
- They come with a 5 second head spin down setting that causes them to park their heads if they have been left idle for more than 5 seconds. As it takes a second or two to spin back up this can result in a very laggy experience during interactive sessions.
- They do not have NCQ or any form of command queing/optimisation. This means that (on FreeBSD at least) you are stuck in the LOOK elevator. In particular this was noticed when doing sequential read & write (think dump|restore tar|untar etc) and interactive tasks simultaneously
- They really suck with FreeBSD and ZFS…
While the other 512-byte sector HDDs were reading/writing at 30MB/s sustained, this EARS model did not exceeded the 1MB/s barrier.
I know for sure that this is related to the 512-byte sector firmware emulation, because the disk works perfectly well if I partition it in a 4k-sector alignment.
The thing is that even in that way, using it in a ZFS RAIDZ configuration the performance is very poor because RAIDZ uses a dynamic stripe size.
The bottom line here is that folks like me, that use different versions of Unix, need the firmware to present the disk as a 4K-sector disk to unleash the full potential of the technology. The OS is already prepared to support that sector size, no need for emulation here.
http://opensolaris.org/jive/thread.jspa?threadID=125702
Some preliminary testing that I have done…the WD20EARS (2TB advanced format drives) actually presents emulated 512byte sectors to the host o/s.
The drive documentation indicates that jumpers 7-8 should be enabled if the o/s does not support advanced format drives – the drive still present 512 bytes sectors.
I have attempted to raise a support ticket querying this, and how one can disable 512byte sector emulation in the drive (perhaps through a firmware upgrade) but I have not received any response to date.
Hopefully is enough people raise support tickets, WD may release firmware that allows the drive to natively present 4k blocks. Other doco indicates several other jumper combinations – all do not seem to make the drive present 4k byte blocks.
Perhaps someone internal to sun that has a relationship with WD may be able to shed some light on this? It would be fantastic to find out that I was just doing something wrong -> then I can get the drives to be seen on 32bit systems (ie – our embedded kit for osol, velitium)
Tested using b133 (64bit intel).
Try to avoid the green drives in ZFS for now. Remember to do your research before you buy a bunch of disks. I was caught off guard by this small change (works fine in win7 etc) which kills performance in ZFS. Ouch.
I’ve had some problems since my upgrade to virtualbox 2.2.0 on OpenSolaris. After some time all of my linux boxes seem to just die. The virtual machine just stops responding. Strangely there was no problem with my windows vms after the update.
From what i can tell it looks like the upgrade turned off “IO APIC” – this is the bit that seemed to cause the problem. Re-enabling this on all of my linux boxes seems to have fixed the problem. I’ll continue testing for another week and update this post if any problems re-occur.
Updated : 01/09/2009
Here is a bit more on IO APIC from the virtualbox wiki… (from a windows perspective)
http://www.virtualbox.org/wiki/Migrate_Windows
The hardware dependent portion of the Windows kernel is dubbed “Hardware Abstraction Layer” (HAL). While hardware vendor specific HALs have become very rare, there are still a number of HALs shipped by Microsoft. Here are the most common HALs (for more information, refer to this article: http://support.microsoft.com/kb/309283):
Hal.dll (Standard PC)
Halacpi.dll (ACPI HAL)
Halaacpi.dll (ACPI HAL with IO APIC)If you perform a Windows installation with default settings in VirtualBox, Halacpi.dll will be chosen as VirtualBox enables ACPI by default but disables the IO APIC by default. A standard installation on a modern physical PC or VMware will usually result in Halaacpi.dll being chosen as most systems nowadays have an IO APIC and VMware chose to virtualize it by default (VirtualBox disables the IO APIC because it is more expensive to virtualize than a standard PIC). So as a first step, you either have to enable IO APIC support in VirtualBox or replace the HAL. Replacing the HAL can be done by booting the VM from the Windows CD and performing a repair installation.
Updated : 5/09/2009
I’ve had even more problems with opensolaris crashing completely after upgrading to the newer versions of virtualbox (3.0.4), and have since reverted back to 2.2.0 which has fixed alot of the hanging issues i have encountered
If you are having problems starting apache on a non-standard port you might find that the problem is related to selinux.
Type this command to check to see what http ports are currently allowed; (remove filter to show all rules)
semanage port -l|grep http
To add another port type the following (with the port you wish to add etc);
semanage port -a -t http_port_t -p tcp 81
If you want to disable selinux completely then go into /etc/selinux/config and set selinux=disabled. Save then reboot.
Setting up LAMP on fedora 11… First install the required modules.
yum install -y httpd.i586 mysql.i586 mysql-server.i586 php.i586 php-mysql.i586 php-gd.i586
Next i’m copying my web source from another linux machine. I’ve run these commands from the destination machine…
cd /var/www/html
rsync -ave ssh 192.168.9.10:/var/www/html/ .
Now my mysql data…
cd /var/lib/mysql
rsync -ave ssh 192.168.9.10:/var/lib/mysql/ .
Accept the certificate and enter the source root password. Next fire up the services… I usually just go into “setup” then “system services” and enable both httpd and mysqld
Reboot. Done
