Date: Fri, 25 Feb 2011 16:09:27 -0700 From: Modulok <modulok@gmail.com> To: Terje Elde <terje@elde.net> Cc: freebsd-questions@freebsd.org Subject: Re: GELI reliability Message-ID: <AANLkTik5R4EaCg6yStPNODmn=5uuBoAuwQ6yicOxwuFH@mail.gmail.com> In-Reply-To: <0847F66E-F541-4604-8238-A869CCDEE163@elde.net> References: <0847F66E-F541-4604-8238-A869CCDEE163@elde.net>
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>> I've used ZFS over GELI in the past, but never had any hardware issues to see how it plays out. I have no idea on that kind of a setup. If I were you I'd make a test system, start an scp command to copy some file from another machine, then start unplugging hard drives. When done, run a diff on the copied file and the original (or at least a checksum) to see if it worked out. I'd do it for you and report back, but at the moment I don't have the hardware to spare. Let us know how it goes ;-) -Modulok- On 2/25/11, Terje Elde <terje@elde.net> wrote: > Hi, > > I'm curious about GELIs theoretical behavior when faced with errors, and > also any experience anyone might have. > > As an example, if I run ZFS with raidz over X drives, then the zpool should > have no issue surviving the complete loss of a full disk. Also, the > familiar "FAILURE - READ_DMA" or READ_DMA48 errors from a disk having a bad > day should also be no issue, certainly not an issue that would result in > crash, or worse still, loss of data. > > What I'm wondering is how much worse off the data would be if I were to > slide inn a GELI layer between the physical drives, and the zpool. > > That is, if I use GELI directly on the individual drives ( /dev/ada0, > /dev/ada1 etc), then make a raidz pool on top of the .eli devices ( > /dev/ada0.eli, /dev/ada1.eli etc). > > For READ_DMA type errors, I suppose GELI could just forward the same errors > up the stack, and that'd be that, the errors wouldn't be any more severe > than what I'd have anyway? > > One exception could be if GELI sector size is larger than disk sector size. > Not being too familiar with GELIs internal workings, I'm not sure that has > to be the case though. GELI sectors have a new IV pr. sector, but the > crypto itself is still done in 128 or 256 bit blocks, so given a single > faulty disk sector, the rest of the GELI sector could still be read and > decrypted? Or are entire GELI sectors faulted if a (smaller) underlaying > sector is unreadable? > > And finally, what if an entire drive dies a cruel and horribly death, all of > it's data returning to the large bit bucket in the sky? Would GELI simply > relay the same errors upstack to ZFS, so ZFS would be able to handle it as > well as it would have without GELI? > > > I've used ZFS over GELI in the past, but never had any hardware issues to > see how it plays out. > > I'm considering deploying it for more stuff now, and reliability wise, from > what I know, I could loose very little by using GELI, or it could be time to > buy napkins, because the risk of a grown man crying while trying to mop up > spilled bits from the floor is increased significantly. > > (backups should avoid the need for tears though, besides, I don't have a > mop) > > Terje > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >
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