Thread (11 messages) 11 messages, 3 authors, 2005-05-03

Re: Any way to Increase MD_SB_DISKS=27 ? I need 31 devices

From: Tyler <hidden>
Date: 2005-05-03 22:28:58

Okay, I will give that a try paul... but i've actually tryed using mdadm 
v2.0-devel to create an array with a version 1 superblock, using only 3 
drives in a raid5 array.  It hasn't worked so far, read my 2 bugreports 
to the mailing list, to see whats happening.. and maybe draw some 
insight from them?  I'm at a loss as to why mdadm is failing right now.. 
even without going over the 27 drive limit.  Neil hasn't responded to 
any emails I've sent regarding this either..

Thanks,
Tyler.

PS - Can you see any kind of order to the "applied" patches on Neil's 
site? .. I can't tell which ones are for the 2.0-devel version and which 
are for 1.9.x .. and one says 1.8 ... etc..

Paul Clements wrote:
Tyler wrote:
quoted
Isn't the superblock still limited to 27 drives though? .. is there 

The version 0.90 superblock is limited to 27 drives. Version 1 
superblock is limited to about 2000 drives, because Neil shrunk the 
amount of per-drive data stored in the superblock drastically. The 
check in mdadm, is in the file mdadm.c, just grep for the message that 
you got ("invalid number of raid devices"). Comment out that code and 
recompile mdadm. Everything should work after that. The kernel you 
have already has support for version 1 superblocks.

-- 
Paul
quoted
maybe a patch for version 1 superblocks that i don't have in 
2.6.12-rc3-mm2, that changes the max drives in the md_p.h and md.c 
driver?  There is only 4096 bytes earmarked for superblocks, and 
within that amount, there isn't enough room to list more than 27 
drives that may be part of the same array.

Do I need some more patches for this to work, that aren't in the -mm 
tree yet?  I was under the impression (from the mdadm v2.0 announce 
file, that anything *after* 2.6.11-rc3 in the -mm tree would have the 
required patches.

Also, where can I disable the check in mdadm?

Thanks,
Tyler.

Paul Clements wrote:
quoted
Tyler wrote:
quoted
PS - I've tryed the latest 2.6.12-rc3-mm2 kernel, with mdadm 
v2.0-devel, using the --metadata 1.0 option on the create line, and 
still get:


quoted
# mdadm -C -e 1.0 -l 6 -n 31 /dev/md0 /dev/hdb /dev/hdc /dev/hdd 
/dev/sda /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg 
/dev/sdh /dev/sdi /dev/sdj /dev/sdk /dev/sdl /dev/sdm /dev/sdn 
/dev/sdo /dev/sdp /dev/sdq /dev/sdr /dev/sds /dev/sdt /dev/sdu 
/dev/sdv /dev/sdw /dev/sdx /dev/sdy /dev/sdz /dev/sdaa /dev/sdab
mdadm: invalid number of raid devices: 31



As far as I can tell, mdadm just shouldn't give this error when 
you're using a version 1 superblock. If you disable that check in 
mdadm.c, I think everything will work. Version 1 superblocks allow 
something like 2000 disks in an array.

-- 
Paul


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