I'm trying to figure out the correct settings for a 7+1 (1TB SATA) RAID5 mdadm software RAID5 setup on SLES 11 SP1.
I'm having a few questions:
1) I notice that "pvcreate" does not support the "--dataalignment" option, which is referenced in several Linux software RAID howto's and wikis ??
2) What would be the best way to setup a ext3 filesystem, without LVM (see 1 - and I can live with it being a single big filesystem).
Currently, what I think about doing is:
a) On each of the 8 disks, create a single primary partition starting at sector 2048 (should solve 512/4096 byte sector stuff)
b) create a RAID5 array (without spare disk) using
mdadm -C /dev/md/mdraid5 --chunk 128 --level 5 -n 8 --force /dev/sda1 .... /dev/sdh1
c) create an ext3 filesystem on the RAID5 device as follows:
mkfs.ext3 /dev/md/mdraid5 -b 4096 -E stride=32,stripe-width=224
(according to 'man mkfs.ext3', stride is the number of filesystem blocks in a RAID chunk, which is 128k/4k = 32. stripe-width is the numer of filesystem blocks in one RAID data stripe, which is (8-1)*128k/4k = 224) about 12
Does anyone have a well-informed opinion about
i) the raid5 chunk size to use (I thought about 128k, this filesystem will mostly host large files, order of GB size)
ii) whether my ext3 parameter derivations make sense
iii) how you would do it (ie setup RAID5 software raid, highest performance possible for a large-file filesystem, on SLES 11 SP1 with 8 1TB SATA disks)
iv) why pvcreate in SLES 11 SP1 is missing the "--dataalignment" option, whether it would still be needed (or the equivalent of it in SLES 11 SP1, what is it?) when using LVM on the RAID5 device
v) is ext3 a good enough filesystem for what I want to do (or is ext3 + software raid5 in this setup bound to be sluggish)? Should I look into ext4/xfs for software raid5 on SLES 11 SP1?