From mboxrd@z Thu Jan 1 00:00:00 1970 From: Remco Hosman Subject: weekend of btrfs findings Date: Tue, 03 Apr 2012 21:11:26 +0200 Message-ID: <4F7B4B5E.4050902@hosman.xs4all.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed To: linux-btrfs@vger.kernel.org Return-path: List-ID: hi, after getting a USB enclosure that allowes me to access each of its disks as individual devices, i played around with btrfs a weekend, and here are some questions i hit, but could not find an answer for. Setup: 4 disks, 2x 500gig, 2x1500gig, connected to a SATA port multiplier backplane to a SATA<->USB converter. PC is a i686 Celeron M, running 3.4.0-rc1, running the latest btrfs tools from git. *) at first, i created the volume as raid10. i started filling it up, and when the 2 500gig disks where full, i got ENOSPC errors. which makes me wonder: what is the advantage of raid10 over raid1? *) i added a 16gig SD card to the array *) with `btrfs balance start -dprofile=raid1 /vol` (the syntax of the -d parameter is not clear in the help --full or man page). this operation completed quite quickly. *) i continued to fill it, and i could put another 100gig orso on the volume before i hit ENOSPC again. but this time, there is plenty of space on the 2 1500gig disks that should be usable right? *) i deleted the 16gig SD card from the array. when i watched this process with dstat, i noticed that its doing lots of writes to the device beeing deleted. why is this? after a while, it failed claiming there was not enough free space. *) i started a rebalance, when i watched this with `btrfs balance status /vol` i showed that is planned to process 549 chunks, when i paused and resumed it, (the pause takes quite a while), it only planned to do 80 chuncks. If i should do more specific tests or provide specific details, please let me know. i have little experience in 'official' testing these kind of things. Remco