> On Apr 24, 2009, at 12:52 AM, Leslie Rhorer wrote:
> > I've done some reading, and it's been suggested a 128K chunk size
> > might be a
> > better choice on my system than the default chunk size of 64K, so I
> > intend
> > to create the new array on the raw devices with the command:
> >
> > mdadm --create --raid-devices=10 --metadata=1.2 --chunk=128 --level=6
> > /dev/sd[a-j]
>
> Go with a bigger chunk size. Especially if you do lots of big file
> manipulation. During testing (many years ago now, admittedly) with
> Dell for some benchmarks, it was determined that when using linux
> software raid, larger chunk sizes would tend to increase performance.
> In those tests, we settled on a 2MB chunk size. I wouldn't recommend
> you go *that* high, but I could easily see 256k or 512k chunk sizes.
I went ahead and selected 256K. There's something a little odd, though.
mdadm is reporting a device size of 2T. These are 1T drives. The overall
array size is correct but the device size is goofy. I hope this doesn't
cause any problems. As I believe I mentioned before (or maybe it was on
another list), I once had problems with ext3 trying to read beyond the
physical end of the array.
RAID-Server:/Backup/Personal_Folders# mdadm -Dt /dev/md0
/dev/md0:
Version : 01.02
Creation Time : Sat Apr 25 01:17:12 2009
Raid Level : raid6
Array Size : 7814098944 (7452.11 GiB 8001.64 GB)
Used Dev Size : 1953524736 (1863.03 GiB 2000.41 GB)
Raid Devices : 10
Total Devices : 10
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Sat Apr 25 01:20:47 2009
State : active, resyncing
Active Devices : 10
Working Devices : 10
Failed Devices : 0
Spare Devices : 0
Chunk Size : 256K
Rebuild Status : 0% complete
Name : RAID-Server:0 (local to host RAID-Server)
UUID : 5ff10d73:a096195f:7a646bba:a68986ca
Events : 1
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 16 1 active sync /dev/sdb
2 8 32 2 active sync /dev/sdc
3 8 48 3 active sync /dev/sdd
4 8 64 4 active sync /dev/sde
5 8 80 5 active sync /dev/sdf
6 8 96 6 active sync /dev/sdg
7 8 112 7 active sync /dev/sdh
8 8 128 8 active sync /dev/sdi
9 8 144 9 active sync /dev/sdj
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