Archive
Posts from 2011
To iPad or not to iPad, that is the question for my readers
Even though I'm your typical IT geek, I'm not one to jump on technology just because it's new. I like to wait until technology stabilizes, prices drop and the lines at your favorite geek store decrease in size. I'm fortunate to have a Macbook Pro, and use it for just about everything I do. While I love my laptop the size and weight have always been a draw back for me…
$ read more →Checking ext3 file system consistency on production systems
As an admin, there is nothing worse that the feeling you get when you determine you are dealing with file system corruption. Wether it's a lost inode or a corrupted superblock, I always get a big knot in my stomach when I figure out that corruption exists. With modern file systems like ZFS it's trivial to check the file system consistency while the server is online. But with older file systems (ext3, ext4, etc.) you typically needed to unmount the file system, run fsck and wait (sometimes for hours!) to throughly check the consistency of the file system…
$ read more →Using the ZFS scrub feature to verify the integrity of your storage
There have been a number of articles written over the past few years that talk about how silent data corruption can occur due to faulty hardware, solar flares as well as software defects. I've seen some oddities in the past that would probably fall into these categories, but without sufficient time to dig deep it's impossible to know for sure. With ZFS this is no longer the case. ZFS checksums every block of data that is written to disk, and compares this checksum when the data is read back into memory…
$ read more →Good write up Linux consistent network device naming
In RHEL 6.1 the default names assigned to Dell server network interfaces changed from ethX to emX and pXpX. The new names describe where a network interface physically resides in the system, and will have the following format: emX the X (first, second, etc.) onboard interface pXpY PCI device X port Y Dell wrote a really good white paper on this, and the following text from the document summarizes how the pieces fit together: "A naming mechanism that can impart meaning to the network > interface‟s name based on the physical location of a network port in > concordance to the intended system design is necessary. To achieve that, > the system firmware has the ability to communicate the intended order > for network devices on the mother board to the Operating System via > standard mechanisms such as SMBIOS and ACPI. > > The new naming scheme uses 'biosdevname' udev helper utility , developed > by Dell and released under GPL, suggests new names based on the location > of the network adapters on the system as suggested by system BIOS." I like the new format, and this will definitely be a nice addition to hardware provisioning systems…
$ read more →Using collectl on Linux to view system performance
I recently needed to figure out what process was generating a bunch of I/O requests on a Linux system. On Solaris, there are a ton of tools available in the DTraceToolkit that can pin down i/o performance consumers. Using iostat in Linux, I can see that the drives are spinning like mad, but I really want to know which process on the machine is driving the disk. Using collectl, we can view this…
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