Monday, 30 May 2011

Case-sensitive Filenames

Linux filenames are case-sensitive, and hence ext filesystems allow files which are only different by upper vs. lower case. Okay, this is to be expected. More interestingly, it is possible to have a directory Test and a file test within the sampe parent directory.

Does not look like we can resolve it gracefully, because under Windows we have to rename one of those. Obviously, it seems better to rename a file. However, this still breaks the program which used a file named test to contain some catalog of the folder named Test.

Wednesday, 25 May 2011

RAID6 progress revisited

The automatic RAID6 recovery algorithm currently in the works will most likely require at least N-1 disks for successful recovery. This is because the Reed-Solomon calculation depends on the order of disks, from which the chicken-and-egg problem results. If two disks are missing, the chicken-and-egg problem seemengly cannot be resolved automatically.

Even as it is with the N-1 requirement, the algorithm looks quite heavy CPU-wise. Looks like the RAID6 recovery implementation would be CPU-bound unlike all other RAID types, which are I/O-bound.

Tuesday, 17 May 2011

Uh oh.

Current progress on RAID6 is that just now looking at the log files I found the latest 48-hour test run botched.

Monday, 9 May 2011

x64 data recovery

We have a 5TB raid 5 ... I think the MBR got messed up and windows server 2003 no longer is able to view the contents of the virtual disk... ... recovery software ... will fail due to the large amount of files we have, about 64 million files.
Some raid software will save the recovered files to another disk.. however 5TB is a large amount of data to save and we do not have any disks or other virtual disks that large.
(from ServerFault)

I suppose we can do that 64 million files, should be interesting to test.

As far as pricing goes, 5 TB swap space is just 3x 2TB WD Caviar Green in RAID 0. At a cost of 4x Caviar Greens you get the same swap space protected by RAID5. At about $60 a pop, the entire lot would cost about $250. The initial cost of purchase is then further offset by putting the temporary drives to use as a backup media.

Monday, 2 May 2011

Simple things first

What is the first troubleshooting step given the following situation

A drive disappeared Windows Explorer. In Drive management the drive are being detected but Volume and Filesystem Type are blank. Everything else is OK (Simple, Basic, Healthy disk and Active, Primary partition).

Actually some of the fancy suggestions were flying around, including, but not limited to bad boot secotors, specific controller model issues, SATA 3 issues, and PSU problem.

Select a white space below to see what was the correct troubleshooting action.

In Disk Management, use Change Drive Letters and Paths and assign the drive letter.

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