Dear All,
We have locked a case at VMware, please find their findings on the same.
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Following the webex session we just had, I've successfully uncovered the root cause of the reported issue to an underlying problem on the block device (either the logic disk, or a problem on the array) being presented to host the datastore in question.
In a nutshell, whenever we try to do raw reads from the disk (from sector 0 onwards), the same ones always fail when we reach the 30932992 bytes (31MB) mark with an IO error (this is consistent, it is always on this region of the disk that read operations fail, no more, no less). This outcome can be seen even when no partition is in the disk (using if=/dev/sdb instead of /dev/sdb1 with dd), and even after zeroing out all the sectors (dd if=/dev/zero of=/dev/sdb). Strangely, read operations work fine (be it writing zeros of random data) along the whole disk. Bear in mind that the tests I did were with non-VMware tools (I pretty much used only dd for these operations), which definitely rules out a VMware problem (in fact, if you were to try to boot the server with a Linux live CD and run the same tests as I did, you would see the same behaviour).
I know that there are no hardware reports of any wrong behaviour on the array, but the data collected with our tests today completely invalidates that. The next step is for you to take this to the server vendor to check for problems on the array or the disks, as they are definitely there and they are the reason for the problem you originally reported.
Please let me know if you have any further questions on this.
Thank you
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David Meireles
Technical Support Engineer
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Now we have locked a case at hardware vendor , let see what will be the next action.
regards
Mr VMware