On 03/14/2011 01:02 PM, Mohit Anchlia wrote: > What RAID level is this? Would RAID 10 or RAID 6 help in such scenarios? Not so much ... if the underlying block device gets corruption, the file system atop it might not be able to survive writing to or reading from a corrupt region. RAID6 could work if you have a read after write function built into the RAID to guarantee that what gets written is what was committed to disk. Most (actually all) hardware on the market at the moment doesn't have this. Some do talk about capability like this, but the real test is to take the write, cache it, compute md5 or similar sums, perform the write, then force a non-cached re-read of the data, and compute then compare the md5 or similar sums. If the sums are incorrect, then reallocating the write to another location and iterating this. Technically, GlusterFS could do this in a translator. Realistically, this would kill performance. RAID10 doesn't compute parity, so you need checksums to see if the data is correct. RAID6 does compute parity (2 different mechanisms), but the implementations can't really identify a failed write/read, as the parity is recomputed at write time, so if corruption occurred in the RAID card (say a failing cache chip, or data cable, or ...), its possible bad data was committed, and the parity data wouldn't reflect a problem. Regards, Joe -- Joseph Landman, Ph.D Founder and CEO Scalable Informatics Inc. email: landman at scalableinformatics.com web : http://scalableinformatics.com http://scalableinformatics.com/sicluster phone: +1 734 786 8423 x121 fax : +1 866 888 3112 cell : +1 734 612 4615
