Flash memory devices not ready to serve as OS drives

To speed boot times, some people try to use flash memory devices as operating system drives. But cost, transfer speed and durability issues make this prohibitively difficult.

To speed boot time, some people have been tempted to substitute flash memory devices for operating system drives. Unfortunately, the way flash devices work makes this prohibitively difficult.

Problem number one is cost. Although flash memory is getting cheaper, a flash drive with the capacity to hold an OS installation would be quite expensive compared to a conventional hard disk. A 4 GB flash drive currently costs approximately $100; a 75 GB Ultra320 SCSI drive from Hitachi currently goes for about $175.

The second issue is transfer speed, which is largely limited by the bus available to the flash device and the interface electronics. Most flash devices seem to top out at around 20 Mb/sec for their read speeds; an enterprise-class hard drive like the above-mentioned SCSI drive can do more than ten times that in both directions.

The third problem with using flash-memory devices as replacements for hard disks is long-term durability. Flash memory is not designed to sustain more than a certain number of write cycles. Most commercial flash-memory products are guaranteed to run for at least 1 million erase/write operations, but there are exceptions to such a norm—so many exceptions, in fact, that it's better to go with technology that has been built from the ground up to support the kind of work involved. Many people believe that flash memory is inherently better than hard drives because of a lack of moving parts. But lack of moving parts doesn't make something immune from wear.

On the other hand, a flash device that's been programmed with a bootable image (such as a bootable ISO for an OS distribution) will usually run many times faster than a CD or DVD of the same data. Since this data is typically read-only, the erase/rewrite cycle limitation doesn't come into play here, so this is a legitimately useful application for a flash device. Substituting one for a system hard drive, though, isn't—at least not yet.

Bottom line: As it stands right now, investing in more conventional solutions is a better investment of your time and money.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter. Check it out for the latest advice and musings on the world of Windows network administrators. He is also the author of the book Windows Server Undocumented Solutions.

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This was first published in June 2006
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