Your SATA RAID has a 56% chance of data loss
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Re: Your SATA RAID has a 56% chance of data loss
#2ZFS however would protect against this, in that it checksums each chunk of data. And "zfs scrub poolname" will go through and do the checksums for you in the event you are storing a lot of data and not necessarily reading/writing it often.
Re: Your SATA RAID has a 56% chance of data loss
#3Note that it mentions that SATA has a higher bit-error rate than SAS/SCSI. Apparently through the use of fewer ECC bits.
But yeah, ZFS rocks.
Re: Your SATA RAID has a 56% chance of data loss
#4ZFS however would protect against this, in that it checksums each chunk of data. And "zfs scrub poolname" will go through and do the checksums for you in the event you are storing a lot of data and not necessarily reading/writing it often.
Well, maybe I should look into transition my home server from Ubuntu and XFS to Nexenta or OpenSolaris and ZFS...
I'd hate to lose some of the data on that thing, though I'm currently not doing any RAID. Just a disk of important stuff rsnapshotted every 4 hours to another disk.
Re: Your SATA RAID has a 56% chance of data loss
#5You could also set smartmon tools to do a short self test every day, and a long one (which reads the entire disk) every week.
At least you'll know if there was an error.
Re: Your SATA RAID has a 56% chance of data loss
#6This is what keeps encryption impractical, especially for laptops.
Re: Your SATA RAID has a 56% chance of data loss
#7Wow. If you have an 8TB raid, that's 7TB of data so 61,572,651,155,456 bits
A hard disk has a bit error rate of 10^15:
1,000,000,000,000,000
That's about 16 times higher.
That's horrible.
Taken to a single 750GB disk that means you can read the entire disk an average of 155 times before you'll encounter an error! That's shockingly bad.
Re: Your SATA RAID has a 56% chance of data loss
#8This is what keeps encryption impractical, especially for laptops.
Why? Assuming you're using CBC mode within each sector, you wouldn't lose any additional data due to a sector error compared to an unencrypted disk.
Re: Your SATA RAID has a 56% chance of data loss
#9ZFS however would protect against this, in that it checksums each chunk of data. And "zfs scrub poolname" will go through and do the checksums for you in the event you are storing a lot of data and not necessarily reading/writing it often.
No, but it will notify you of a problem. However, I suspect that smartmontools would do an even better job of notifying you of a problem before it even occurs.
If you want something that will actually protect against bit level errors well, generate some extra data using an appropriate Error Correcting Code for your important archives/files. Something like what par2repair generates. This is incredibly slow compared to simple erasure codes like RAID uses, though. There are some filesystems that do this for you automatically, I wrote one:) Actually, other than that I don't know of any filesystems that do this.
If the above is impractical for performance reasons, Google recommends mirroring everything on three disks...
Re: Your SATA RAID has a 56% chance of data loss
#10This is what keeps encryption impractical, especially for laptops.
Why? Assuming you're using CBC mode within each sector, you wouldn't lose any additional data due to a sector error compared to an unencrypted disk.
These are bit level errors. So instead of losing a bit or two, you lose a massive chunk. That's the difference between a strange character in your Doc file and losing the whole thing.
I think it's 128 bits for truecrypt, although internet searches point to many people using higher (1024 and 4096). And if the bit level error rates are as high as he says, looks bad.