On Tue, 18 Dec 2007, Thiemo Nagel wrote:

Dear Norman,

quoted

quoted

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


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Quite slow?

10 disks (raptors) raid 5 on regular sata controllers:

# dd if=/dev/md3 of=/dev/zero bs=128k count=64k
65536+0 records in
65536+0 records out
8589934592 bytes (8.6 GB) copied, 10.718 seconds, 801 MB/s

# dd if=bigfile of=/dev/zero bs=128k count=64k
27773+1 records in
27773+1 records out
3640379392 bytes (3.6 GB) copied, 6.58454 seconds, 553 MB/s