Re: [CinCV] grand'ma proxy / RAID
Christian Thaeter <ct@...
2012-05-05 21:54:25 GMT
Am Sat, 05 May 2012 16:10:27 -0500
schrieb Tim Copeland <tim@...>:
> 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@...>:
> > > 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
> 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 :)).
> > 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.
> > >
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