[opensuse] mirroring & striping thoughts
Hi, all -- I can finally talk to my two new 4T drives (see my GPT post); yay. Now to think about data protection. I have for a long time used "poor man's mirroring" by mounting two devices and keeping content in sync across them. Not only does it give me undelete capability because operations happen on each dev separately, but it also ensures that I'll have a working disk if my system dies and I have to start over with, say, some live-image build. The other thing I usually do is carve off a small partition at the back end of the disk in which to store device and content information; that's a simple DOS FS readable by anything and so no matter what I can find what pieces are what. On the other hand, it's a pain to keep the two in sync. Now that I've discovered SuSE Studio and shouldn't ever have to fall back to a generic ISO boot, perhaps it's time to think about actual mirroring, or even striping and mirroring. I have these 2ae 4T drives plus a pair each of 500G and 400G drives; I could at least stripe the smaller ones into almost-1T virtual disks, or maybe I string together all three (do I actually stripe, or merely concatenate, since other than that they are all SATA I don't really know the relative speeds?) on each side to get almost 5T (which of course would look like 4.5T in binary numbers; stupid disk manufacturers!) of uninterrupted space. But I'm a newbie as well as easily worried :-) Meanwhile, disks only get bigger (and stay full :-) and so I expect that I'll be swapping smaller for bigger occasionally. If I've striped my two smallest disks onto my large one, how do I pull out one to replace it with Tomorrow's Big Guy? Maybe I leave the 4T alone and at most only stripe the smaller into 1T of "secondary" space; then I simply have to buy the next disk as bigger than my smallest chunk rather than bigger than my current total. Hmmm... What are your thoughts on software RAID in general, especially regarding striping & mirroring (which would definitely require RAID to recover) vs mirroring alone (which should allow me to just use the disk in any ol' system without RAID involved if I had to), and can you recommend any primers or HOWTOs for the nervous guy? :-) TIA & HAND :-D -- David T-G See http://justpickone.org/davidtg/email/ See http://justpickone.org/davidtg/tofu.txt
David T-G wrote:
What are your thoughts on software RAID in general, especially regarding striping & mirroring (which would definitely require RAID to recover) vs mirroring alone (which should allow me to just use the disk in any ol' system without RAID involved if I had to), and can you recommend any primers or HOWTOs for the nervous guy? :-)
I've been using software RAID for almost 10 years, no particular thoughts come to mind. It works. -- Per Jessen, Zürich (15.4°C) http://www.hostsuisse.com/ - dedicated server rental in Switzerland. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
David T-G said the following on 10/23/2013 06:59 AM:
I have for a long time used "poor man's mirroring" by mounting two devices and keeping content in sync across them. Not only does it give me undelete capability because operations happen on each dev separately, but it also ensures that I'll have a working disk
If recovering changes - undelete - is the issue then why not use 'snapper'? http://doc.opensuse.org/products/draft/SLES/SLES-admin_sd_draft/cha.snapper.... And not only with BtrFS... -- How long did the whining go on when KDE2 went on KDE3? The only universal constant is change. If a species can not adapt it goes extinct. That's the law of the universe, adapt or die. -- Billie Walsh, May 18 2013 -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
Anton, et al -- ...and then Anton Aylward said... % % David T-G said the following on 10/23/2013 06:59 AM: ... % >me undelete capability because operations happen on each dev separately, % >but it also ensures that I'll have a working disk % % If recovering changes - undelete - is the issue then why not use 'snapper'? % % http://doc.opensuse.org/products/draft/SLES/SLES-admin_sd_draft/cha.snapper.... Mainly because I hadn't heard of it :-) I've been a NetApp Filer user for years in my corporate life and have long wanted this. YIPPEE! I'll definitely be looking into this. % And not only with BtrFS... So, even though the doc says BtrFS only, XFS or ReiserFS will happily support snapper? Thanks again & HAND :-D -- David T-G See http://justpickone.org/davidtg/email/ See http://justpickone.org/davidtg/tofu.txt
В Wed, 23 Oct 2013 11:24:15 -0400 David T-G <d13@justpickone.org> пишет:
% And not only with BtrFS...
So, even though the doc says BtrFS only, XFS or ReiserFS will happily support snapper?
No. There is experimental support for ext4 with LVM snapshots but it requires special LVM tools that are not available in standard distribution.
Andrey Borzenkov said the following on 10/23/2013 12:50 PM:
В Wed, 23 Oct 2013 11:24:15 -0400 David T-G <d13@justpickone.org> пишет:
% And not only with BtrFS...
So, even though the doc says BtrFS only, XFS or ReiserFS will happily support snapper?
No. There is experimental support for ext4 with LVM snapshots but it requires special LVM tools that are not available in standard distribution.
Curious. Since the LVM snapshot mechanism works underneath the file system by copying the partition/logical volume, that seems odd. Could you give more details please. If you mean 'snapper', then yes, perhaps, since snapper works at the FS level and requires a COW FS. -- "He is the Napoleon of crime, Watson. He is the organizer of half that is evil and of nearly all that is undetected in this great city. He is a genius, a philosopher, an abstract thinker. He has a brain of the first order. He sits motionless, like a spider in the center of its web, but that web has a thousand radiations, and he knows well every quiver of each of them. He does little himself. He only plans. But his agents are numerous and splendidly organized. If there a crime to be done, a paper to be abstracted, we will say, a house to be rifled, a man to be removed -- the word is passed to the Professor, the matter is organized and carried out. The agent may be caught. In that case money is found for his bail or his defence. But the central power which uses the agent is never caught -- never so much as suspected." -- Sherlock Holmes, in "The Final Problem" -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
В Wed, 23 Oct 2013 13:26:03 -0400 Anton Aylward <opensuse@antonaylward.com> пишет:
If you mean 'snapper',
Yes, I do. The question was about what filesystems are supported by snapper. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
Andrey Borzenkov said the following on 10/23/2013 01:33 PM:
В Wed, 23 Oct 2013 13:26:03 -0400 Anton Aylward <opensuse@antonaylward.com> пишет:
If you mean 'snapper',
Yes, I do. The question was about what filesystems are supported by snapper.
Snapper works on COW file systems. Nothing to do with LVM. LVM has its own snapshot mechanism which works at the LV level regardless of the file system. COW - Copy On Write - is a feature used by SSD files systems and is available also on ZFS, BtrFS, ext3cow, http://faif.objectis.net/download-copy-on-write-based-file-systems ext3cow: https://www.usenix.org/legacy/events/fast04/wips/peterson.pdf http://www.ext3cow.com/ext3cow/Welcome.html ZFS: http://www.ext3cow.com/ext3cow/Welcome.html or in user-space http://user-mode-linux.sourceforge.net/old/UserModeLinux-HOWTO-7.html -- "The easiest thing to do in the world is to neglect the important and give in to the urgent." -- Denis Waitley -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
David T-G said the following on 10/23/2013 11:24 AM:
% And not only with BtrFS...
So, even though the doc says BtrFS only, XFS or ReiserFS will happily support snapper?
Red the detailed docs, not just that page. RESEARCH! Godaminit, Jim! WTF do you think google is for, eh? The requirement is a COW file system. Such as the ext3cow extension. Have a COW man. Production is not the application of tools to materials, but logic to work. --Peter F. Drucker -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
participants (4)
-
Andrey Borzenkov -
Anton Aylward -
David T-G -
Per Jessen