Re: όταν οι δίσκοι κάνουν σιωπηλά λάθη τι μας σώζει?

[Nick Demou]

Φυσικά μετά από αυτά που έπαθα έψαξα πιο σοβαρά το btrfs και από ότι
φαίνεται θα βοηθούσε ΠΟΛΥ εφόσον φρόντιζα να ελέγχω με κάποιον τρόπο
τα logs (ομολογώ ότι δεν το έκανα και ο αναμάρτητος ας μου πετάξει την
πρώτη πέτρα) -- ορίστε τι βρήκα:

https://btrfs.wiki.kernel.org/index.php/FAQ
<< What checksum function does Btrfs use?>>

# Currently Btrfs uses crc32c for data and metadata. The disk format has
# room for 256bits of checksum for metadata and up to a full leaf block
# (roughly 4k or more) for data blocks. Over time we'll add support for more
#  checksum alternatives.


http://www.linuxfoundation.jp/jp_uploads/seminar20081119/JapanLinuxSymposiumFSTalk.pdf
<<Next Generation File Systems and Data Integrity,
rwheeler at redhat.com, November 2008>>

# BTRFS supports checksumming of all data
# Checksums are validated on read
# With internal mirroring, a block with a bad checksum or IO error can
#  be requested from the other mirror


http://ptspts.blogspot.com/2010/06/does-btrfs-survive-silent-disk-data.html
<<2010-06 Does Btrfs survive silent disk data corruption in RAID1 mode?>>

# Some of my experimenting with Btrfs in Linux 2.6.34 yielded the
following results:
#
#     * If only one disk (out of two) contains corrupt data, then Btrfs detects
# some checksum failures, and then recovers (overwriting the corrupt data
# with the corresponding good data from the other disk).
# This works even if the corruption happened while the filesystem was mounted.


http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg03756.html
<<Re: What protection does btrfs checksumming currently give?>>
jim owens, 07 Jan 2010

# First, understand that a checksum only says "this block is good or bad".
# The checksum can not be used to "reconstruct" the data.
# Checksums are present for all btrfs blocks unless you explicitly shut
# them off with mount/ioctl/fcntl options.
# To have a good copy you can use as a replacement block, you must
# use either btrfs raid1 or raid10.
# [...]
# If you have btrfs raid, it will find the good block on a read, but
# AFAIK we don't have tools yet to automatically reallocate the bad one.


-- 
"The software is licensed, not sold" -- MICROSOFT LICENSE TERMS