Messages in this thread | | | Date | Tue, 25 Aug 2009 16:48:45 -0700 (PDT) | From | david@lang ... | Subject | Re: [patch] ext2/3: document conditions when reliable operation is possible |
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On Tue, 25 Aug 2009, Ric Wheeler wrote:
> On 08/25/2009 07:26 PM, Pavel Machek wrote: >> >>>>> Basically, any file system (Linux, windows, OSX, etc) that writes into >>>>> the page cache will lose data when you hot unplug its storage. End of >>>>> story, don't do it! >>>> >>>> No, not ext3 on SATA disk with barriers on and proper use of >>>> fsync(). I actually tested that. >>>> >>>> Yes, I should be able to hotunplug SATA drives and expect the data >>>> that was fsync-ed to be there. >>> >>> You can and will lose data (even after fsync) with any type of storage at >>> some rate. What you are missing here is that data loss needs to be >>> measured in hard numbers - say percentage of installed boxes that have >>> config X that lose data. >> >> I'm talking "by design" here. >> >> I will lose data even on SATA drive that is properly powered on if I >> wait 5 years. >> > > You are dead wrong. > > For RAID5 arrays, you assume that you have a hard failure and a power outage > before you can rebuild the RAID (order of hours at full tilt).
and that the power outage causes a corrupted write.
>>> I can promise you that hot unplugging and replugging a S-ATA drive will >>> also lose you data if you are actively writing to it (ext2, 3, whatever). >> >> I can promise you that running S-ATA drive will also lose you data, >> even if you are not actively writing to it. Just wait 10 years; so >> what is your point? > > I lost a s-ata drive 24 hours after installing it in a new box. If I had MD5 > RAID5, I would not have lost any.
me to, in fact just after I copied data from a raid array to it so that I could rebuild the raid array differently :-(
David Lang
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