Incidentally, that paper came up in a ZFS-related thread on Ars Technica just the other day (as did the link to the FreeNAS forum post). Let me just quote what I said there:
> The conclusion of the paper is that ZFS does not protect against in-memory > corruption, and thus can't provide end-to-end integrity in the presence of > memory errors. I am not arguing against that at all; obviously you'll want > ECC on your ZFS-based server if you value data integrity -- just as you would > if you were using any other file system. That doesn't really have anything to > do with the claim that ZFS specifically makes lack of ECC more likely to > cause total data loss, though. The sections you quote below basically say that while ZFS offers good protection against on-disk corruption, it does *not* effectively protect you against memory errors. Or, put another way, the authors are basically finding that despite all the FS-level checksumming, ZFS does not render ECC memory unnecessary (as one might perhaps naively expect). No claim is being made that memory errors affect ZFS more than other filesystems. On Feb 26, 2014, at 10:24 PM, Philip Robar <philip.ro...@gmail.com> wrote: > Thank you for your reasoned and detailed response and subsequent followup. > This was exactly what I was hoping for. > > I'm curious, have you read, End-to-end Data Integrity for File Systems: A ZFS > Case Study by Zhang, et al? > > Abstract: present a study of the effects of disk and memory corruption on > file system data integrity. Our analysis focuses on Sun’s ZFS, a modern > commercial offering with numerous reliability mechanisms. Through careful and > thorough fault injection, we show that ZFS is robust to a wide range of disk > faults. We further demonstrate that ZFS is less resilient to memory > corruption, which can lead to corrupt data being returned to applications or > system crashes. Our analysis reveals the importance of considering both > memory and disk in the construction of truly robust file and storage systems. > > ...memory corruptions still remain a serious problem to data integrity. Our > results for memory corruptions indicate cases where bad data is returned to > the user, operations silently fail, and the whole system crashes. Our > probability analysis shows that one single bit flip has small but > non-negligible chances to cause failures such as reading/writing corrupt data > and system crashing. > > Phil > > > -- > > --- > You received this message because you are subscribed to the Google Groups > "zfs-macos" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to zfs-macos+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out.
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