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Apr
15
comment Can BTRFS stripe RAID arrays?
A quick review of the btrfs wiki (btrfs.wiki.kernel.org/index.php/…) indicates that, once it is stable, btrfs will be able to reshape raid arrays, i.e. add and remove elements from a raid array without loss of data. This is a piece missing from ZFS so clearly makes it the better choice.
Apr
15
comment Can BTRFS stripe RAID arrays?
Thanks for the information. After playing with the btrfs space allocator its clear that the information I was missing was that btrfs automatically stripes the data. AFAIK, md can only use equal size elements (in fact the current version warns if any element differs in size by more than 1%). If I understand correctly, btrfs automatically does the equivalent of mdadm /dev/md0 -C lraid5 -n4 /dev/sd{a,b,c,d}1;mdadm /dev/md1 -C -lraid5 -n3 /dev/sd{a,b,c}2;mdadm /dev/md2 -C -lmirror /dev/sd{a,b}3 plus create the volume. I obviously need to read up on it a bit more! (as well as waiting a while...)
Apr
11
awarded  Nice Answer
Apr
8
comment Does ZFS for Linux over stress VirtualBox?
Thanks for the comment. That's the information I was looking for. I suspect that most people who've run ZFS (or ZoL) in a VM have just tried a few simple operations and haven't tried moving hundreds of files into pools running on raid sets. The only reference I found said it was a timing issue in VirtualBox which it was thought had been fixed, but was then reopened. I suspect ZFS is just pushing the simulation to its limit, expecting it to behave like real hardware. Now I've got most files in place in the VM, the errors have (mostly) stopped.
Apr
7
revised Does ZFS for Linux over stress VirtualBox?
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Apr
7
awarded  Curious
Apr
6
revised Does ZFS for Linux over stress VirtualBox?
Added ZFS version
Apr
6
asked Does ZFS for Linux over stress VirtualBox?
Mar
25
awarded  Nice Answer
Mar
17
comment What are the overheads of using multiple smaller raid devices versus partitioned raid devices as physical volumes?
Having got into the habit of using separate VGs (and moving them occasionally), I've since created them for other things, e.g. keeping all GIT repositories separate. I am thinking of merging some now as the separation serves less purpose since I changed hardware, but I currently have a few which are only a few dozen Gigabytes, which is wasteful of a 700Gb PV, hence my question.
Mar
17
comment What are the overheads of using multiple smaller raid devices versus partitioned raid devices as physical volumes?
Mostly historical. Original VGs were OS, home directories, MythTV recordings, ISO+disk images and backup. OS/home separation was from install. Recordings were separate simply to keep a better handle on usage and allow them to be moved to bigger disks as I changed hardware. The ISO and virtual disk images were put in their own VGs so they could be on faster physical disks (I intended to put them on SSDs, but never got around to it). Backup was separate to put VG on 2 mirrored USB drives - keeping a long term backup simply meant unplugging a drive, replacing it and letting the mirror rebuild.
Mar
16
comment What are the overheads of using multiple smaller raid devices versus partitioned raid devices as physical volumes?
@Bratchley I didn't think that multilevel partitioning would have a noticeable performance impact but was looking for confirmation. This is a home system and they are local disks. Over the past few years, I've been in the habit of separating different sets of files onto different volume groups, but as my setup has evolved, the majority of raid (md) devices are about 700Gb in size (after partitioning the underlying 3Tb disks into 12). I'd rather keep some of the volume groups significantly smaller than this, hence the sub-partitioning of the raid devices. Thanks for the input.
Mar
14
asked What are the overheads of using multiple smaller raid devices versus partitioned raid devices as physical volumes?
Mar
6
answered What is the correct way to set up sw RAID1 so either drive boots?
Mar
5
comment Can BTRFS stripe RAID arrays?
@Bratchley thank for the edit - comes from typing late and night, cutting and pasting and poor proofreading...
Mar
5
comment Can BTRFS stripe RAID arrays?
That's something that surprised me. Although BTRFS is included in many (most?) distros as standard, it's not really considered "stable". Meanwhile, ZFS, which seems much more stable, mature and functional is still an add-on (although I suspect part of this is use of none-free code somewhere). I think I'll stick with ext4/lvm2/md for now (as it's really stable/tested/etc and I understand what it's doing) and just run the others on test systems. I'd still be interested to know if BTRFS can create the filesystem I'd like to use.
Mar
5
asked Can BTRFS stripe RAID arrays?
Nov
4
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18
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Jun
17
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