[linux-lvm] Mirror: write operations and consistency checking

Ray Morris support at bettercgi.com
Fri Jun 3 03:18:50 UTC 2011

It is safe to use a flash drive. The first generation flash drives had an endurance of only about 50,000 writes, but current devices test better than magnetic disks, lasting for about 51 years of continuous writes. Part of that is better chips. Part is that even inexpensive flash devices now have wear leveling, so it rotates blocks, not writing to the same physical block even if you write to the same logical block.
Ray Morris

vincent <lvmml at vinvin.dyndns.org> wrote:

>Greeting LVM developers and users,
>I've been using the LVM mirror on several LVs and for some time now,
>using a core log. I'm tired of the resource intensive initialization on
>each boot, and I'm considering using a flash device as the third disk
>for the mirror's log.
>My question is thus: are there some write operations happening onto the
>log while there is no activity on the mirror's files? Is there some
>of periodic background thread checking for the consistency of the
>and writing the status to the log, or is it safe to use a flash disk
>low activity mirrors?
>>From what I understood, a bit is used on the log for each region
>(512k-default) on the mirror. Does It means that if a 100M file is
>written on the mirror, the log will be written 200 times on the same
>block? Or is there a queue that holds log write operations and syncs
>them to the log disk periodically to prevent that? That would be nice,
>and even nicer if it was adjustable.
>linux-lvm mailing list
>linux-lvm at redhat.com
>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

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