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Re: [K12OSN] backend raid 1, raid 5 or none of the above?



Thanks to everyone for the ideas and advice.

On 8/7/07, Huck <dhuckaby paasda org> wrote:
> If backups are your main concern...checkout BackupPC...
>
> Then you can mirror the OS...
> and use BackupPC for /home
>
> --Huck
>
> Terrell Prudé Jr. wrote:
> > john wrote:
> >> Hi all,
> >>
> >> I am waffling on a question that I hope you all will be able to help
> >> me come to a resolution about. Should my backend file storage system
> >> be software raid 1 or software raid 5 or non of these? OS is Linux of
> >> course. My LTSP server resides on a different machine entirely.
> >>
> >> I've already setup a RAID5 system with 3 active disks and one hotswap
> >> by following a very good howto
> >> http://www.debian-administration.org/articles/512
> >>
> >> My final setup uses /dev/md0 in a raid 1 config using 10 Gb to host
> >> the OS and mbr
> >> and /dev/md1 in a 1 tb raid 5 to host the file system which has been
> >> partitioned with separate /home, /tmp , /usr, /var
> >>
> >> However the more I think about it the more I am worried that I am
> >> setting myself for pain in the future. I am thinking about dumping the
> >> whole setup and going to  raid 1 for the following reasons:
> >>
> >> 1. My reading tells me that RAID 1 has a longer MTBF
> >> http://en.wikipedia.org/wiki/RAID_1#RAID_1
> >>
> >> 2. RAID 1 offers redundancy similar to raid5 but also relative
> >> simplicity because I can clone one of the disks and keep a copy around
> >> in case of problems
> >> 3. RAID 1 offers comparable disk read times when compared to RAID 5
> >>
> >>
> >> On the other hand:
> >>
> >> RAID 5 offers large volume sizes which we are looking for
> >> RAID 5 offers comparable disk read times when compared to RAID 1
> >> RAID 5 doens't offer comparable MTBF rates as RAID as you factor in extra disk
> >> RAID 5 may be more complex to administer or rebuild than a "simple" mirror
> >>
> >> Perhaps if I am such a coward I should go with a single 500 gig disk,
> >> and make a backup image with G4U or a hardware disk cloner (which we
> >> have) and keep it on hand and do a incremental backup of student files
> >> every night (which we intend to do anyway). That way, although
> >> students might not have access to their resources for a day, at least
> >> I would have a path to recovery that I already understand.
> >>
> >> As a side note we have frequent power outages do to weather, isolation
> >> etc, and I haven't looked into setting up linux to talk to UPS's. Is a
> >> raided system more intolerant of having the plug pulled than a normal
> >> Linux box running ext3?
> >>
> >>
> >> waffle, waffle, waffle :-)
> >>
> >> I hope folks will set me straight!
> >>
> >> Thanks,
> >>
> >> John
> >
> > If I were you, I'd go with hardware RAID 5 with, say, an LSI Logic
> > MegaRAID card or something similar.  I imagine that the ability to
> > replace a failed disk quickly--preferably on the fly--is important,
> > since you're considering something like RAID.  Others may differ, but I
> > find that, for me, hardware RAID 5 offers the best balance of capacity
> > per disk, speed, quick recovery from a failed disk, and expense.
> >
> > Actually, my own RAID (I built one recently) is a RAID 5 with six SATA
> > disks and an LSI MegaRAID 150-6.  It works quite nicely indeed and
> > didn't break the bank.
> >
> > If you need something *very* reliable, then RAID 50 would be your bet.
> > If you need balls-out speed and good reliability, RAID 10 is your bet.
> >
> > --TP
> >
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> >
> >
>
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