G-Technology G-RACK 12, Руководство пользователя

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F.A.Q.
p. 259
Like:
• Performance - it›s usually good, and it generally «does the right thing» with ssds.
• It doesn›t eat RAM the way zfs does.
• Subvolumes make volume management and snapshot management easy.
• Can de-fragment (unlike zfs)
• Can dedupe out-of-band, so unlike zfs this can be done without huge memory requirements
Dislike:
• Not fully stable. Don’t get me wrong. I do believe it’s ready for day to day usage even for
production systems. But you still have to be cautious. You should look up known problems or
limitations before using some features. For example the conversion from ext seems to have
problems since Linux 4. Some of them are not problems/bugs in BTRfs but other programs that
have not been found yet.
• General growing pains (not everything supported on every configuration.)
• qgroups (every time I›ve hit a bug, it›s been here.)
Hate:
• Performance with virtual machine images and databases is simply bad. I know about NoCow but
it turns off checksumming.
• Encryption has been talked about for years, but is nowhere on the road map.
• RAID is limited to two disks of redundancy, and this might be by choice since a patch to allow
nearly arbitrary levels of redundancy in RAID was submitted years ago. I keep hoping this is just
attributed to growing pains and BTRfs RAID›s immaturity, but I can›t be sure.
Why BTRfs is awesome?
Ok, so BTRfs is stable enough to be trusted. Or at least with companies whose judgment has way
more value than most like Facebook and SuSE Linux experts. At this point, if you still don’t trust it,
stop reading this post and keep using ext4 or xfs, no problem.
But if you are thinking “maybe I can use BTRfs on my next Linux deployment”, why should you
consider it? Well, because it has some great features! The page linked at the beginning has the
complete list, here I’m going to list the ones I prefer the most.
BTRfs has been designed from the beginning to deal with modern data sources, and in fact is able to
manage modern large hard disks and large disk groups, up to 2^64 byte. That number means 16 EiB
of maximum file size and file system, and yes the E means Exabyte. This is possible thanks to the way
it consumes space: other file systems use disks in a contiguous manner, layering their structure in a
single space from the beginning to the end of the disk. This makes the rebuild of a disk, especially