[H-GEN] Idea for journalling filesystems

[Christopher Biggs]

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Jason Parker-Burlingham <jasonp at panix.com> moved upon the face of the 'Net and spake thusly:

> What I would like to know is whether a USB drive or some similar
> technology would present a good block device to use as a journal which
> lives off-disk.

My experience with USB flash drives.

1.  They present as SCSI block devices.

2. They're really slow, at least when using USB1.x.  USB 2.0 
   devices cost quite a bit extra.

3.  At least on 2.4.2x kernels, you can't trust the kernel's idea of
    the disk size, if you're hot swapping cards of different size
    (eg, remove a 64M card insert a 32M one, kernel still thinks
    /dev/sda is 64M).

4.  They do have a limited life, 10^4 to 10^5 write cycles.

--cjb


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