FR1 2.15b

FR1 is a Linux kernel driver that adapts the kernel's own software RAID1 driver.
FR1 is a Linux kernel driver that adapts the kernel's own software RAID1 driver.

It's intelligent in that it doesn't blindly resynchronize a whole mirror component when only a few blocks need resyncing. That can save hours of resync time on a large device. In addition, it always chooses the fastest device to read from on reads.

The driver keeps a bitmap of pending writes in memory, and writes them to the mirror component that's just been repaired when it comes back on line. The bitmap is two-level and created pagewise on demand, so it's not too expensive.

A terabyte sized device with blocks of 4K will cost max 32MB of memory per mirror component, thus 64MB max for a two component mirror.

But in practice only a few pages of bitmap will have been allocated by the time you come to fix the device.

Limitations:

Ditto for arrays with spare components. The 2.4 kernel code is very obscure in the area of array management and I can be excused! The situation has bettered in 2.6, but it is still not perfectly obvious code.
I really don't know what to do about mirror components that have a nonzero offset recorded for them in the array metadata. I've never seen it in the field. Probably things will go horribly wrong.

last updated on:
October 14th, 2005, 8:05 GMT
price:
FREE!
developed by:
Peter T. Breuer
homepage:
www.it.uc3m.es
license type:
GPL (GNU General Public License) 
category:
ROOT \ System \ Operating Systems \ Kernels

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