On Sat, 2012-05-05 at 23:54 +0200, Christian Thaeter wrote:

Am Sat, 05 May 2012 16:10:27 -0500 schrieb Tim Copeland <tim-pq2sHRfyv0yACnhNS6V4X+TW4wlIGRCZ@public.gmane.org>: > On Fri, 2012-05-04 at 18:32 +0200, Christian Thaeter wrote: > > > Am Fri, 04 May 2012 17:45:21 +0200 > > schrieb Haldun ALTAN <altan-39ZsbGIQGT5GWvitb5QawA@public.gmane.org>: > > > > > Well that was no more, for a long time, about Grand'ma proxy but > > > about RAID > > > > > > May be this not the exact place to talk about RAID but indirectly > > > offers a better use of cinelerra. I think :)) > > > > > > I just wanted to send a link about a very good tuto on how to > > > RAID on ubuntu or others. It's just like the vidéo but very much > > > more specifique. > > > > > > http://www.dedoimedo.com/computers/linux-raid.html > > > > apart from that tutorial, here are some tips for the raid level and > > setup from my experience: > > > > for anything valuable (aka, your work) you want raid10 > > with 3 or more drives. Thats not mentioned on the tutorial above > > but the linux kernel can do raid10 since quite some time. > > > You can use RAID 10 on only 2 drives. > > > > > This gives fast read speed, average write speed and redundancy on > > the cost of 50% storage utilization. Speeds scale up as more drives > > you add. > > > > If you have only 2 Drives then choose Raid1, Performance and safety > > is comparable to the Raid10 above. > > > > This is not the case. Yes you get the safety but no you don't get the > performance. > Linux RAID 1 only reads from a single disk, so the performance is > comparable to a single drive. > It was thought at one time that Linux RAID 1 did parallel reads, but > this is false. I have personally > done the benchmarking and my findings were conclusive. Plus you can > find modern documentation > to support my findings. > > If you seek redundancy and performance, use RAID 10. > Linux RAID 10 is supported on as few as 2 drives. nice to know that, I never benchmarked raid1 as I only use it for boot/system partitions but not data (except on our server .. maybe I shall change that? do you know if raid1 is upgradeable to raid10? i am being to lazy to rtfm now :)).

Thats a good question. Unfortunately, that is not possible as far as I know.  That will require
a lot of scary data juggling. Your question prompted me to poke around a bit to see what I
could find on the topic. Here is an interesting post from others doing that type of migration.

http://www.burgundywall.com/tech/convert-raid1-to-raid10-with-lvm/

On a side note:
When the new btrfs file system goes main stream, it supports many neat RAID and LVM type features natively.
I do believe converting from one RAID type to another on the fly will be possible then. Heavy development is surrounding
btrfs , and is looking to be nothing short of impressive. Kernel support already exists, so its possible to play around with it
on a test system. However, it wont be viable for real world until they get the check disk finished for it. I highly recommend
keeping look out for this. I cant wait for this file system to mature.

> > > If you have a fast computer with lots of RAM and lots of HDD's (4+) > > then you may try to evaluate raid5 or raid6, but be aware that write > > speeds are quite low and benchmark this before you using it > > seriously. Reading scales well with the number of disks you have. > > Makes a good vault for archiving files but might be too slow for a > > working area (considering video work). Anyways this once worked for > > me. > > > > Finally stay away from Raid0, it brings double (or more) the speed > > for double (or more) the risk. HDD's *WILL* fail eventually, its > > only matter of time and Murphy's law tells this happens when you > > are least expect it! This makes only sense for data you can > > *extremely* easy recover like volatile cache files (Background > > rendering), Files you grabbed from a cam and which are still > > available on a fast medium (no you don't want to grab all tapes > > again!). For anything else, don't even consider it. > > > > Don't forget to make regular Disk checks (regular badblocks > > (readonly) checks and then Raid-resyncs with mdadm in daemon mode) > > which will try to repair damaged data. Having a smartd running is > > nice to find out about if one of your drives will fail soon in few > > cases, but doesn't substitute for the disk checks above as > > smartchecks don't enforce a repair of damaged data and abort on the > > first found error, leaving any potential bad data ahead > > undiscovered. > > > > And finally: RAID redundancy is only an insurance against Harddisk > > failures but does *not* substitute for a backup, one manual mishap > > destroying data can not be undone. > > > > Christian > > > > > > > > Hope helps. > > > > > > Haldun. > > > > > > _______________________________________________ > > > Cinelerra mailing list > > > Cinelerra-0LiWvn2yMWjUKW2QJMybhA@public.gmane.org > > > https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra > > > > _______________________________________________ > > Cinelerra mailing list > > Cinelerra-0LiWvn2yMWjUKW2QJMybhA@public.gmane.org > > https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra > > _______________________________________________ Cinelerra mailing list Cinelerra-0LiWvn2yMWjUKW2QJMybhA@public.gmane.org https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra