Making a Flash Raid thing

[derchris]

How about that:

Quad-CF PCI Controller from Addonics

[scombo]

Hi Funkstar,

1) Yes, I checked before buying. The Transcend and A-Data 266x CF cards are all locked in "True IDE" mode (unlike all Sandisk 266/300 cards which are set to "removable").

2) All of the 266x Transcend cards will (should!) support fixed disk installations. Looking about it should be possible to format the card in FAT32 then just stick it on the IDE connector and treat it like any other formatted HDD. That's the theory, anyway. Yet to be proven until I get that adaptor from HK.

If my tests go well then it's a couple of 8GB cards on my christmas list. Or perhaps one 8GB 266x and one 16GB 133x UDMA4 card (similar price). One for system and one for work/data. The 133x card has a transfer rate of 25MB/s read/write which isn't unlike the old Tosh 1.8" HDD in the laptop now. Still might suck so I'm considering sticking with 16GB overall.

Hi Mikerr,

I see we're not being "cutting edge" then.. How depressing. Still, at least you show that the theory is sound! The difference today I suppose is that the fastest CF cards are able to rival or beat HDD's for overall perfomance as well as sound/heat/energy/robustness. If not beating them in pound per gigabyte..

-Stuart

[scombo]

derchris,

Thanks. That's a wicked looking product! Interesting comment at the bottom of that page that Agent might be interested in:

"*note: Only fixed disk Compact Flash can be used to create RAID sets. Removable type CF can only be used as individual drives. Use the SilCfg Management utility to see whether the CF card is fixed disk or removable type CF. Otherwise, use Diskpart which is included with Windows XP."

Seems there is a difference between removable and fixed disk CF cards.

-Stuart

[Agent]

Just spent about an hour reading up on this (never come across if before!)...there seems to be loads of misinformation out there

From what I can tell, there is no electronic / technical difference from a fixed type compared to a removable. It seems that its just a flag thats set on the device itself.

There also seems to be some references to a tool made by San-Disk that can change this flag, but its under NDA. Some searching might be able to find it...

Programming the CompactFlash card / Memory Stick

A Memory Stick simulates a "big diskette", so with the FAT specifications and the lay-out of the boot sector in hand, we have all the information that we need. It is a different story with a CompactFlash card, though: a CompactFlash card mimics a hard disk (or "fixed disk" if you are used to IBM terminology). That means that a CompactFlash card is partitioned, just like a hard disk.

For a hard disk (and on a CompactFlash card), every partition is like a large diskette. A FAT partition has a boot sector, which contains a BIOS Parameter Block; it has one or more reserved sectors, two FATs and a root directory. The information about the partitions themselves, however, is in another table, inside another boot record: the Master Boot Record (MBR). The Master Boot Record is also a 512 byte sector. This sector contains a partition table with four entries starting at offset 446. Each partition table entry is 16 bytes long. The first 446 entries typically contain a bootstrap program that the BIOS uses to, well, boot the machine; the last two bytes are a signature and should contain 0x55aa (the same signature as for a standard boot sector).

Initially, disks were addressed with values for the cylinder, the head (platter) and the sector; this is called CHS-addressing. With a single byte for each of the number of cylinders, the number of heads and the number of sectors per cylinder, the maximum addressable size for a disk is 224, or 16777216 sectors. With a sector size of 512 bytes, the maximum disk size could never exceed 8 GiB (if you look up references on CHS addressing, you will find that the sector and cylinder values are packed together in a single 16-bit word, but for the back-of-the-envelope calculation it comes up with the same result). To accommodate large disks, an alternative addressing scheme was developed: LBA (Logical Block Addressing). This is essentially a linear sector number. Fortunately, the partition table contains the start of the partition and its size in both CHS and in LBA values.

On a CompactFlash card, you must therefore first browse through the partition table (which starts at the absolute offset 0x1BE, from the start of the disk) and find the start of the partition. When jumping to the partition, you will then stumble upon a boot record containing a BIOS Parameter Block. Then you can proceed to locate and decode the FAT and the root directory, keeping in mind that all offsets in this BIOS Parameter Block are relative to the start of the partition.

CF Adapter General FAQ
Also has a bit more, but very vague info.

Seems I was somewhat incorrect Funkstar

Now, I'd love to have a look at 2 CF cards, one being removable and one being fixed. I wonder how far could be got (changing their type) by looking at them with some of the low level disk editing tools out there...?

[Agent]

A computer with no hard drive based on flash memory: Page 2 - 59Hardware

General public Compact Flash cards are usualy recognized as removable hard drives under Windows, the Extreme IV being one as well. Indeed, only SanDisk's industrial series are recognized ase fixed disks under Windows. In reality the removable or fixed state of the cards depends on a flag located within the firmware, modifiable under msdos environment using some rare programs.

Modifying the default firmware, as done on our extreme IV, is a delicate operation not to be taken lightly. However, this step is essential in order to successfully install Windows on the card.

So those tools are out there

[Funkstar]

Misinformation? In the tech industry? really?

it's one of the reasons i decided not to use a couple of Extreme IVs for booting my media box. I couldn't justify spending all that cash and now have it work.

I'll have a proper read of those links later Agent. That last link sounds interesting

[this_is_gav]

I've got a VIA Eden (or something) based system somewhere around here that has a CF adapter mounted directly to the motherboard. I've never tested as those systems are crap for anything beyond a router or something (and the largest CF card I have is a 512mb at most I think), but I assume it works.