Re: Raid over 48 disks

[Thiemo Nagel <thiemo.nagel@ph.tum.de>]

Dear Norman,

>> So... we're curious how Linux will handle such a beast. Has anyone run 
>> MD software RAID over so many disks? Then piled LVM/ext3 on top of 
>> that? Any suggestions?
>>
>> Are we crazy to think this is even possible?

I'm running 22x 500GB disks attached to RocketRaid2340 and NFORCE-MCP55
onboard controllers on an Athlon DC 5000+ with 1GB RAM:

9746150400 blocks super 1.2 level 6, 256k chunk, algorithm 2 [22/22]

Performance of the raw device is fair:
# dd if=/dev/md2 of=/dev/zero bs=128k count=64k
65536+0 records in
65536+0 records out
8589934592 bytes (8.6 GB) copied, 15.6071 seconds, 550 MB/s

Somewhat less through ext3 (created with -E stride=64):
# dd if=largetestfile of=/dev/zero bs=128k count=64k
65536+0 records in
65536+0 records out
8589934592 bytes (8.6 GB) copied, 26.4103 seconds, 325 MB/s

There were no problems up to now.  (mkfs.ext3 wants -F to create a 
filesystem larger than 8TB.  The hard maximum is 16TB, so you will need 
to create partitions, if your drives are larger than 350GB...)

Kind regards,

Thiemo Nagel