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Re: [K12OSN] Re: RAID 10



Owen O Donovan wrote:

(Aside) Thanks for the reference to the  material re rocketraid.  I'm
interested is setting up a bunch of NAS boxes and was looking at that as an
option.

The following are some notes about raiding focused around smaller terminal
server systems (30 - 60) users on 2 to 4 drives.   It seems to me that going
beyond that number is where you want to pull out the storage component and
make it independent of the terminal server hardware.

In addition to the redundancy benefit of a mirror (RAID1) which Jim spoke to,
the read access behaves just like striping. So a 2 drive mirrored system is
capable of supporting many more users than a single drive. Since common usage
patterns are  generally "attribute intensive" (listing directories, getting
file sizes etc)and reading smaller files, the net impact of using a simple
mirror is substantial. Stats from hdparm bear this out

Applications and usage patterns make a difference. On a small box, RAID1 holds
its own for home directories because most accesses are attribute reads. As the
size of your server goes up, RAID 5 is good economical home directory
solution: Your added cost for redundancy is only 1 additional drive/partition
(or 2 drives/partitions if you want hot spares).




so, are you saying that your idea of a small terminal server is 30-60? do you mean 30 to 60 logged on at any one time?

I have almost 500 users, but never more than 35 connected at the most, at any one time. 400 of the users are elementary students, and they don't really use the system that heavilly. Their home directories are virtually empty. the 150 or so high school students directories are used , but like I say, only at a maximum of 35 users at any one time. I only have 35 terminals.

Someone else told me that 30 users at a time was doable on an EIDE system, with acceptable performance. Not great performance. but acceptable

I thought if I added a raid configuration I could get halfway decent performance out of my server. along with data redundancy


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