I am going to buy my first laptop soon (Dell 1505n). I understand that notebooks typically have slow hard disks, and that USB-mounted flash drives are much faster. I also guess that they would use less energy, though I haven't seen any pages documenting those facts.

So, I am interested in putting my Linux distribution on a flash drive. I am wondering about partitioning. I read that you don't want the swap partition on a flash drive, because it will use up all the read/erase cycles that the flash memory can take. Is there anything else that shouldn't be mounted on the drive? Perhaps /dev?

Also, I was thinking of the USB drive as a security measure. Put the bootloader on the USB drive instead of the hard disk and if someone steals your laptop, they can't boot the machine up! Of course, that is only if this works in the first place.

Thanks in advance for feedback and discussion on this topic.

Not true. I assume you are talking about drive speed in RPM versus throughput. A 7200 RPM drive is supposed to be ~14% faster then a 5400 RPM drive so Dell says. But that is hard to believe.

An IDE interface using UDMA 133 is 133 Megabytes per second versus USB 2.0 at 60 Megabytes per second. BTW Serial ATA is 150 Megabytes per second. There are other factors like access times that also effect how fast data is read from a hard drive but a USB drive will not be faster.

Yes, it is possible to boot linux from a USB Flash drive however, IMO just having the boot loader on the USB drive is not a good security practice. A flash drive will not be big enough to hold much data and so anyone with some basic knowledge could still gain access to your information. Encrypting the drive is the best method.

While the transfer rate indicates absolute maximums, I'm not so sure they represent typical, real-world transfer rates. *If* the USB drive is able to use 90% of it's available bandwidth, while the conventional laptop hard drive is only able to use 10%, the USB drive will be much quicker. Either way, USB drives should have much less latency as hard drive spin-ups should take much more time than whatever form of electronic scanning a flash drive uses. However, with the increase in HD cache, perhaps the mobile drives can offer comparable latency.

This article tests some mobile hard disks.

http://www.storagereview.com/2005notebook.sr?page=0%2C0

Unfortunately, they don't compare them to USB flash memory. The disks they review have access times that are measured at 14-18 ms, even though they are all listed around 12ms. Transfer rates are in the 20-40 MB/s range, and they tend to have 300-400 IO/s.

Dell's site lists the cheap HD (which I would probably get) as being SATA interface, 5400 RPM, 12 ms access time, 2 MB buffer, and a 5 second spindle starts time. So, because of the smaller buffer, it will probably be a little slower than the hard disks reviewed in the article, and will not come close to maxing out the SATA bandwidth.

Unfortunately, I have yet to find people doing this kind of testing on USB flash drives. I think I will test the flash drives I have, and then post the data.

Hi,

I'm also interested in putting a linux distro on a usb flash drive. I'm not concerned with security, as much as I am concerned with performance and noise. I know there are quiet hard drives out there, but I have specific reasons for a usb flash drive.

Like HawkeyeCoug asks, what paths need routinely available write access so I can place those in the hard disk, off of the flash drive? I only want as many read-only paths as possible to reside on the flash drive.

And, instead of creating multiple partitions for each of these paths on the hard disk (and consequently losing space on the drive), can I mount loopback files that can grow and shrink for these paths?

Thanks for any help you can offer,
Sam

I still haven't found any articles directly comparing USB drives and laptop drives. However, I did find a review by Ars on flash drives. Here is the original:

http://arstechnica.com/reviews/hardware/flash.ars/6

Here is their "updated" article, though it is still only 2005:

http://arstechnica.com/reviews/hardware/flash2005.ars/8

In the first article from Ars the drives peaked out at around 10 MB/s transfer, and in their second they peaked out at about 20 MB/s. My guess is that new drives probably have slightly faster flash, and probably peak out at around 25 MB/s. Even then, the transfer rate of USB flash drives looks to be around half of that for laptop hard drives, depending on file size. It looks like flash memory used in USB devices is slower than I anticipated, and it is not just the USB bus slowing it down.

I will still test boot times when I get my laptop, but I don't anticipate significant speedups.