Re: Scrub CPU usage ...

[George Mitchell <george@chinilu.com>]

On 05/05/2013 02:22 AM, Martin Steigerwald wrote:
> Hi George!
>
> Am Samstag, 4. Mai 2013, 11:39:59 schrieb George Mitchell:
>> the next update.  I am using btrfs raid 1 across five 500GB Seagate
>> nearline drives and btrfs single on a Seagate 4TB backup drive.  I am
>> absolutely delighted with how this system is working.  This is my
>> primary day in and day out system.  I have to date hard crashed this
>> system at least three times without sustaining any apparent damage to
>> the filesystems.  Perhaps I have just been extremely lucky, but it seems
>> like most of the major holes have been closed at this point.  Actually I
>> have only two significant issues currently with btrfs.
> Are you aware that BTRFS RAID-1 works differently than block based RAID? BTRFS
> will only be holding two copies of every data or metadata chunk on two
> different drives, regardless how many drives you use. So only one drive may
> fail.
>
> Well, I think you will have notices with df output for the filesystem, but I
> thought I mention it, just in case.
>
> Thanks,
Yes indeed!  I was aware of this from the beginning.  All I am looking 
for is duplication across hardware.  The advantage of more than two 
drives is that in case you lose a drive, you don't end up losing a lot 
of space, and you are much less likely to end up in an unduplicated 
state for a significant amount of time.  But thanks for your thoughts!  
What I am NOT missing about the old 3ware card is the resyncs.  I used 
to spend half a day doing drive resyncs when a drive dropped out for 
some reason.  Hardware RAID is great when it works, but I much prefer 
btrfs.  Software RAID has its own problems.  Its gotten better I hear, 
but when I used it for a long time, I was a pain.  But both forms of 
block RAID saved me from ever losing data.  - George