q: BLOCK_SIZE
This is a repost, basically. When I posted this question for a first time (8 Dec 2000), noone answered, but there was a way low traffic on this list that time...
Little question that I already posted here a long time ago. What drawbacks can suffer if one changes BLOCK_SIZE in include/linux/lvm.h from 1024 (or 4096 on S/390) to 512? I can't understand from code what't a real purpose of this constant, -- lvm seemed to work well with BLOCK_SIZE=512, no troubles so far, -- but i'm still not shure if it is "legal" to change that. At least there is some purpose on having different values for this constant on S/390 and other platforms, -- again, can't see that purposes...
This is about using lvm with rawio -- on 2.2, rawio wan't work with i/o size be not a multiple of blocksize, while on 2.4 it works. Or at least this was on Dec-2000.
Oh yes, this is about 2.2 kernel and lvm-0.9.
Thank you.
Regards,
Michael.
Quoted 3 lines · Michael
Little question that I already posted here a long time ago. What drawbacks can suffer if one changes
BLOCK_SIZEininclude/linux/lvm.hfrom 1024 (or 4096 on S/390) to 512?
On S/390 it would appear that the DASD block devices have a 4096 byte sector size. However, on most other systems there is only a 512 byte sector size, so I don't see any reason there would be problems with BLOCK_SIZE = 512.
I think Andrea Arcangeli was complaining about this as well.
Quoted 4 lines
This is about using lvm with rawio -- on 2.2, rawio wan't work with i/o size be not a multiple of blocksize, while on 2.4 it works. Or at least this was on Dec-2000. Oh yes, this is about 2.2 kernel and lvm-0.9.
If it works for you at 512 bytes, leave it then. Maybe Heinz will let us know why it is set to 1024 bytes.
Cheers, Andreas
Signature · 3 lines
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- DogbertQuoted 11 lines · Andreas Dilger
Quoted 3 lines · Michael
Little question that I already posted here a long time ago. What drawbacks can suffer if one changes
BLOCK_SIZEininclude/linux/lvm.hfrom 1024 (or 4096 on S/390) to 512?On S/390 it would appear that the DASD block devices have a 4096 byte sector size. However, on most other systems there is only a 512 byte sector size, so I don't see any reason there would be problems with
BLOCK_SIZE= 512.I think Andrea Arcangeli was complaining about this as well.
I checked Andrea's patch into cvs, try and see.
- Joe
Quoted 10 lines · Andreas Dilger
Quoted 3 lines · Michael
Little question that I already posted here a long time ago. What drawbacks can suffer if one changes
BLOCK_SIZEininclude/linux/lvm.hfrom 1024 (or 4096 on S/390) to 512?On S/390 it would appear that the DASD block devices have a 4096 byte sector size. However, on most other systems there is only a 512 byte sector size, so I don't see any reason there would be problems with
BLOCK_SIZE= 512.
Quoted 8 lines
I think Andrea Arcangeli was complaining about this as well.
Quoted 4 lines
This is about using lvm with rawio -- on 2.2, rawio wan't work with i/o size be not a multiple of blocksize, while on 2.4 it works. Or at least this was on Dec-2000. Oh yes, this is about 2.2 kernel and lvm-0.9.
If it works for you at 512 bytes, leave it then.
Yep.
Quoted 2 lines
Maybe Heinz
will let us know why it is set to 1024 bytes.
It is basically an approach to support larger LV sizes than 2T :)
Because the Linux kernel supports 2^32 blocks per block minor up to version 2.4, this is one approach (with tradeoffs for sure) to raise that limit.
With the 4k block size on S/390 DASD devices this means 16T per LV!
Sure: we won't have a satisfying solution before Linux 2.5.
Quoted 10 lines
Cheers, Andreas
Signature · 7 lines
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert _______________________________________________ linux-lvm mailing list [email protected] http://lists.sistina.com/mailman/listinfo/linux-lvm
Signature · 15 lines
Regards,
Heinz -- The LVM Guy --
*** Software bugs are stupid.
Nevertheless it needs not so stupid people to solve them ***
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