Slashdot Mirror
Cluster Harddrive Using Firewire?
Ironstorm asks: "Recently I've started to see Firewire harddrives being sold from companies like Maxtor & Western Digital and now I'm pondering firewire storage solutions for high-availability clusters. Does anyone know if it would be possible to share a harddrive between two cluster nodes on a Firewire bus? Or have a node mount another node's Firewire drive if the other node has failed?"
In the fc/scsi world, you can send reserve, release, and reset signals. Server 1 goes down, server 2 trys reserve, if server 1 died too fast to release, reserve fails, server 2 resets ownership (blows reserve away), server 2 reserves, server 2 up and running with storage. I am not sure how firewire storage works (are the ops scsi like, the same fc ops are?), but I would geuss you would have something similar. Not it just depends if the host OS supports an application sending this ops accross. Then a cluster manager application can handle it. Perhaps the cluster manager needs to run at or in conjunction with some clustering device drivers but you get the picture. Should work...
-- soldack
NTFS and I believe FAT 32 (don't know about FAT 16) partitions retain memory of what their letter was. Win2k and NT4 will simply try that letter, if it is in use it will move up until it runs out. This keeps applications in line that reference the c: style notation. The problem is that c: is really just a symbolic link to a disk number and partition number. This link is not a UNIX one that is made through the file system but made at the device driver level.
The problem occurs when some software does not use a file system and does direct disk access. Some databases do this for example. This type of software usually does not use a drive lettered partition. It relies on disk and partition numbers and may or may not get broken when the numbering changes. Win2k disk and partition numbering is simpy based on discovery order. This in turn is based on the order in which drivers are loaded and where hardware is located on PCI and storage buses (SCSI/FibreChannel/FireWire). Put a new FibreChannel card in front of your old scsi and suddenly the database doesn't work. Write a special driver for you superduper disks that loads before the standard win2k driver and you may screw things up.
As others of noted Win2k supports mounting now. This lets you just have C as a sort of "/".
As for driver letters on firewire things should go like this in the win2k world:
PCI (if firewire pci card) or root bus driver (built into mother board) finds firewire bus, loads firewire bus driver.
Standard firewire bus driver finds device.
An additional driver or two will load some or all of which would be vendor specific. It could run like the standard scsi port driver/ vendor scsi miniport combonation. It would present an upword interface the same as presented by the normal scsi port/miniport combo but send firewire out the bottom.
This would let the standard pnp disk, partition, and file system drivers load on top.
They would talk scsi ops down the stack where the firewire scsi port/miniport would translate and encapsulate as needed and send it out, using the Firewire bus driver. Numbering occurs as things are discovered. Letters are assigned to partitions trying to use what was stored, moving up letters if a conflict occurs.
-- soldack
A firewire network is not restricted to a single 'host'. Several computers can be plugged into a firewire network and share the peripherals on it. Similarly, the computers can communicate with each other as well. The only problem I can see is that only one computer can actually mount a drive at the same time. However, a system that would allow a second computer to mount a drive if the first failed should be trivial to implement.
in NT (4.0 or 2000) you can directly assign letters to hard drives with the hard disk manager. I don't known if win9*/ME does honor these flags.
Nobody uses it. Apple, even though they use FireWire, is still into Little Boxes All Over The Table. Granite Microsystems sells some small Device Bay racks and a very few devices to put in them. As far as I know, nobody else actually has Device Bay products.
1394 - Ask for it by Number.
A (long, Flash-based) message from the 1394 trade association.
Yes. Dual hosting the SCSI bus to keep the storage available even if a node fails has been available for at least ten years, if not even longer. I can't possibly imagine that such wouldn't work with firewire, too.
Umm... wait. You are using VMS, right? Or do you want to give us some clue what kind of operating system and hardware you plan to use this on?
Slashdot is jumping the shark. I'm just driving the boat.
Okay...
Slightly off topic
How does windows assign drive letters to these drives? My "cold swap" pullout IDE drives require a reboot (in win 9x/nt/2k ) so the drive letters can be assigned. Even worse, the drive letters change on my Primary Master drive when I add/remove my secondary Slave drive.
FYI, Linux doesn't require a reboot as long as a hard drive was detected on bootup. And obviously drive letters & Mount points are not a problem.
Does windows require some add on software for Firewire Drives? Or will it simply just add a drive letter for each partition.
Anybody care to share their 2¢?
Apparently, according to Maxtor (skip to Q-17), sharing of devices between multiple computers is not an available ability.
You can accomplish anything you set your mind to. The impossible just takes a little longer.