Storage Features: Where Are They?

By Henry Newman

I know the economic situation has been poor for three-plus years, but a host of technologies are needed to address critical issues, and these technologies were all promised before the downturn. The two critical ones in my opinion are ANSI T10 Data Integrity Field AKA Protection Information (DIF/PI) and declustered RAID. The T10 DIF passes a checksum from the HBA to the disk, which is checked at the disk and back at the HBA on the return. It works only with SAS or Fibre Channel drives and cannot work with SATA drives. With the addition and validation of this checksum, the potential for silent data corruption goes way down. My understanding is about seven orders of magnitude better detection of silent data corruption.

Declustered RAID is in the same boat. I wrote about this over two years ago in "RAID's Days May Be Numbered". In that time, not much has changed except disk drives have gotten bigger, and we are closer to hitting the wall and going splat. With 4 TB drives announced and nearing the market, I think vendors that do not have declustered RAID are about to get a rude awaking when data loss will be commonplace.

Both of the features have been promised by many vendors time and time again, with little to no movement forward. I totally get the economic situation, but just making new denser faster products does not help underlying reliability and data integrity issues. I am hearing more and more cases of data loss with failures of RAID-6 LUNs. The solution is well known and has been thoroughly discussed. It is just waiting for the vendors to solve. The question is when? We must to require these technologies when we write specification or at least an upgrade path.

This article was originally published on September 27, 2011