[Techtalk] formatting half a mirrored raid...

Walt pippin at freeshell.org
Fri Jun 13 14:49:54 EST 2003

Maria Blackmore wrote:
>can you post the contents of your raidtab for md0 please?

The entry for this raid is...

     raiddev /dev/md0
     raid-level              1
     nr-raid-disks           2
     persistent-superblock   1
     chunk-size              32

     device                  /dev/hda1
     raid-disk               0
     device                  /dev/hdd1
     raid-disk               1

>You may wish to consider an external storage array that uses u160 SCSI as
>the bus protocol to communicate with the host computer, but you stack it
>full of cheap, commodity IDE drives.

Well, I have an external 8-bay SCSI 160 case
and I was planning on stacking it full of SCSI
drives as they were needed... Apparently I should
have asked for input here first.

Our theory was that since the case only cost $150,
and storage costs are dropping (plus we've had
some miserable reliability experiences with IDE in
the past that were NOT operator related :-Þ) adding
new SCSI drives will gradually become cheaper...

>The idea being that because you have
>hot spares online and ready to go, and would be using RAID5, the loss of a
>less reliable IDE drive will not be harmful, and can be quickly and
>automatically rebuilt on the spare drive.  The loss of an individual drive
>will not harm anything else, since all the caddies are hotswappable, and
>each drive is on a seperate IDE bus.

Okay, so what is this kind of device called?
What do I look for if I want to buy one? That is
what I was hoping to find, some inexpensive
way to string IDE drives together, but everything
I found seemed to start at $2500 and rapidly
climb from there...

>Failing that, I have a friend who's selling a pair of EMC storage arrays,
>good for 18 TB each. :)

Emailing you off-list...

>I always advocate the use of backups, in which case a small DLT changer
>would probably work out quite well for you, though there are better
>technologies starting to appear nowadays.  A single DLT cartridge should
>be good for 40 GB of uncompressed data.

We have DLT now, 12/24. If I used that, it would take
8 tapes just to make one backup of our main server.
(2:1 compression never really seems to happen...)
Not only that, but tapes still cost c. $10-15 each. So
every two backups, I could have purchased a new
120 gb IDE hard drive.

What we are considering is an external IDE firewire
drive that we will just switch out IDE drives in to
make backups. Plus tapes take forever!

>The cost of a ... SCSI convertor...

And I didn't see something like this! I need to
find better sources for information. Well, or better
utilize the ones I have. I tried searching google
(more informative than the wretched retailer's sites)
but end confused at the dramatic price range
between products that sound like their doing the
same thing: http://www.allmediait.com/html/pricing.html

Anyway... *sigh* thanks for your help and patience!



     Millions long for immortality who do not know what to do with
     themselves on a rainy Sunday afternoon.
                         Susan Ertz 

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