What are the replacement options for an IDE hard disk for a DOS based system?
I have got a few "embedded" systems running MSDOS 6.2 which boot from and store data to IDE hard disks. Since these drives are nearing their end of life, the question arises how we can replace them.
The requirements are:
- DOS must be able to install and boot from these drives.
- They must be able to sustain heavy (mostly) write access.
- If possible, they should be able to survive moderate vibrations (not too bad since the current hard disks have survived several years of that)
I considered the following options so far:
- other ide hard drives: Unfortunately modern IDE drives are too large so DOS cannot boot from them even if I create small partitions. Older IDE drives are just that: old, so they are probably not the most reliable ones any more.
- SSDs: There are a few SSDs with IDE interface available. I have not yet tried them. Does anybody have any experience with them? They look like the ideal replacement provided that DOS can boot from them and that writing speed does not deteriorate too much (the old hard disks are no race cars either).
- Compact Flash: There are adapters for using CF with IDE controllers and they work fine. DOS can boot from them and they have no problems at all with vibrations. What I am not sure about is their durability. DOS uses FAT so some very few sectors are written every time the medium is being written to.
- IDE to SATA converters: I have no idea whether they are any good. Has anybody tried them? It might be an option to use one of these to connect an SATA SSD to the system.
Are there any alternatives that I have missed? (We are working on replacing these systems, but it will still take a few years.)
This is not really an answer to the question but I want to describe what we actually did so somebody else might profit from it as well:
In one of the systems the hdd died. We have replaced the drive with a CompactFlash to IDE adapter. As a safeguard against failure we have provided a second CompactFlash with an image copy of the original so if it goes bad it is easy to replace. The data written to it is copied to another system at least once a day so the most we stand to lose is one day's data. Not ideal but it could be worse.
It has been working fine since March 2011.
We will replace the CompactFlash on a yearly basis to reduce the probability of failure.
I use Emphase IDE Flash Modules that I purchase from Logic Systems. They are based on the more reliable SLC flash memory technology, and are designed as hard disk drive replacements in embedded systems. They are a little larger that the connector itself (40 or 44-pin), and generally plug right into the board or at the end of the cable with no fuss. They are available in small 256MB, 512MB, and 2GB sizes to work with legacy system limitations.
This is the short description from the site:
The new Emphase FDM 4000X series flash module is the ideal medium for developing embedded, solid state platforms. It plugs directly into a standard 40-pin IDE port to act as a hard drive. With no moving parts, wide temperature range, Master/Slave switch selectable, and R/W endurance of 2,000,000 times, the FDM 4000X increases the range of environments and operating configurations your system can withstand. The wear-leveling algorithm extends the module's lifetime and performance by evenly spreading the media usage across all pages in the flash. Also, the FDM 4000X supports most operating systems, including Windows XPe and Linux.
They have high read/write speeds (40MB/20MB), and SMART functions to warn you as you are approaching the 2 million write limits, something you won't get with a generic IDE to xFlash adapter. I have used them with Classic Mac OS, DOS, Linux, and Amiga OS based systems.
They have built in ECC, and an MTBF of 3 million hours. I have yet to have one fail over the past 3 years.
Have you considered IBM Microdrives in conjunction with a CompactFlash > IDE adapter? These moving-parts hard drives were the basis for the old iPod Nano, so are certainly good for the job if it involves a some movement and vibration. Sadly these will probably have to be sourced via eBay but they are pretty handy.
You might also want to consider what software may potentially offer good write caching for DOS. If there's some way you could virtualise the software on these systems in something like VirtualBox, the in-built statistics will give you a good profile of how much wear leveling you'll require of your replacement device.
You might try creating a bootable DOS environment using the Win98SE Bootable Floppy method. (You may need to have a computer running win98SE)
Copy himem.sys and emm386.sys from c:\windows\command to the root of the new drive if needed. Use notepad to create a config.sys and type
device=himem.sys
device=emm386.sys
It will boot to DOS just fine. It should be able to run all the old DOS programs, recognize FAT32, and create larger partitions than 2 gb.
IDE hard drives should still be available. I have seen an IDE to sata controller recently as well.