Monthly Archives: January 2011

Firefox 3.6 – new tab opening order – fix

25-Jan-2011 Posted by Sonia Hamilton under
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… in Firefox 3.6 however only new tabs are opened at the far right of the tabbar while new tabs that are opened from existing tabs, e.g. by middle-clicking a link in an already open tab, are opened next to the tab containing the link … about:config … filter for the term tabs.insertRelatedAfterCurrent. The default value of the parameter is true which simply means that related tabs are opened after the current and not at the end. A double-click on the row will change the value to false indicating that related tabs will from then on be opened at the end of the tabbar just like new tabs

Full article at ghacks.net.

Solaris – increase tmpfs /tmp on the fly

24-Jan-2011 Posted by Sonia Hamilton under
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A useful script from BigAdmin for increasing the size of a tmpfs /tmp without rebooting. See also SoftPanorama, Talking about RAM disks in the Solaris OS.

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The RAID5 Write Hole

14-Jan-2011 Posted by Sonia Hamilton under , ,
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The latest edition of the venerable UNIX and Linux System Administration Handbook (Nemeth et al) has a good section discussing the “RAID5 Write Hole”:

Finally, RAID 5 is vulnerable to corruption in certain circumstances. Its incremental updating of parity data is more efficient than reading the entire stripe and recalculating the stripe’s parity based on the original data. On the other hand, it means that at no point is parity data ever validated or recalculated. If any block in a stripe should fall out of sync with the parity block, that fact will never become evident in normal use; reads of the data blocks will still return the correct data.

Only when a disk fails does the problem become apparent. The parity block will likely have been rewritten many times since the occurrence of the original desynchronization. Therefore, the reconstructed data block on the replacement disk will consist of essentially random data.

Further reading on the BAARF archive (Battle Against Any Raid 5), including why RAID10 and RAID3 should be chosen over RAID5. And then there’s ZFS and RAID-Z.

Using ZFS on Solaris to rapidly build systems

12-Jan-2011 Posted by Sonia Hamilton under
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A work colleagues used an interesting technique to rapidly build some Solaris systems. We usually use Jumpstart but due to the large number of identical systems to be built, he had to use a faster method. In a nutshell:

  • build the first system onto a single disk with a root zfs partition
  • export the root partition onto a second hard disk
  • on subsequent machines insert this second hard disk, import then re-export the root zfs partition
  • when finished, add a second hard disk to all machines and zfs mirror the root partition. Fix up hostname, network, etc

Another possible method would be to break mirroring, re-mirror on second machine, as so on.

Thanks Peter.

Blown my iPhone data usage…

04-Jan-2011 Posted by Sonia Hamilton under ,
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Oops, I’ve blown my iPhone data usage over Xmas/New Year. Was watching too much pr0n (aka Brazilian Jiu Jitu competitions).

The nice Telstra guy gave me a good tip – disable “Cellular Data” and “Enable 3G” in my network settings (until my next billing cycle), so as not to really blow out my usage and get a $1000 bill.

The Apple Discussions forum discusses the difference between the two settings – it seems disable “Cellular Data” stops internet access; disable “Enable 3G” forces MMS’s to be sent via the edge network. But I didn’t read the page in detail, as I’ve got lots more pr0n to watch, from my ADSL connection :-)