[luau] videl.ics.hawaii.edu disk failure - Your Help Needed

[Warren Togami]

On Wed, 2003-12-03 at 23:38, Thomas Ryan Gordon Sr wrote:
> >> We should get another 60GB drive to mirror the other 60GB drive.
> >> Preferably of the same model so they both run with similar speed and
> >> access times.  The exact model is $99 at local CompUSA, but I'm looking
> >> for better deals elsewhere.  newegg might be the best deal because after
> >> shipping it is lower than $99, without taxes.
> >
> >
> > I went ahead and bought us a 160 gb Seagate 7200 rpm ata100 8mb cache 
> > drive for the server.  We can mirror the other 60 gb drive and either 
> > add to our storage or mirror 100gb of it.  Let's determine who to give 
> > it to so that it can be installed.  A lack of redundancy makes me 
> > anxious, so it is ready when we are.
> >
> > --scott
> >
> Isn't it best to run an array with identical drives?  What kind of raid 
> controller are you using that won't waste 100G when mirroring a 60G?
> 
> Tom

RAID works most efficiently yes with identical drives.  Software RAID
works no problem with drives of different sizes and speeds, but
unfortunately efficiency is lost because the array must run at the speed
of the slower disk.

160GB 7200rpm 8MB cache
60GB  7200rpm 2MB cache
Unfortunately this means that Videl will still be limited in performance
to the 2MB cache of the smaller disk.  While the 60GB system drive
portion can be made redundant across both disks, using the non-redundant
100MB portion eats into the disk bandwidth on the larger disk, which
blocks and slows down the entire system.  This itself is not entirely
bad, just inefficient.

For the reasons above I am saddened that the drive was bought after
little discourse.  It was my belief that my proposed plan in my last
post with the new 60GB disk and moving the 120GB disk to Oceanic mirror
was the most effective use of money and resources, but since the drive
was already bought we *can* use it if Scott wishes it so.

How much did that drive cost Scott?

If the cost was low enough, it may actually be advantageous to buy
another identical 160GB drive and simply replace both 60GB drives
currently in Videl.  Otherwise, if the one 160GB drive was bought in
Hawaii and is currently unopened & easily returnable, I would much
prefer to simply replace the dead drive with an identical 60GB drive. 
That would have the lowest money cost, least amount of labor, and
greatest efficiency in operation.

Warren