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

[Huck]

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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