On 10/01/12 8:39 PM, Keith Keller wrote: > The controller node has two 90GB SSDs that I plan to use as a > bootable RAID1 system disk. What is the preferred method for laying > out the RAID array? a server makes very little use of its system disks after its booted, everything it needs ends up in cache pretty quickly. and you typically don't reboot a server very often. why waste SSD for that? I'd rather use SSD for something like LSI Logic's CacheCade v2 (but this requires you use a LSI SAS raid card too) > 2) With large arrays you often hear about "aligning the filesystem to > the disk". Is there a fairly standard way (I hope using only CentOS > tools) of going about this? Are the various mkfs tools smart enough to > figure out how an array is aligned on its own, or is sysadmin > intervention required on such large arrays? (If it helps any, the disk > array is backed by a 3ware 9750 controller. I have not yet decided how > many disks I will use in the array, if that influences the alignment.) I would suggest not using more than 10-11 disks in a single raid group or the rebuild times get hellaciously long (11 x 3TB SAS2 RAID6 took 12 hours to rebuild when I ran tests). if this is for nearline bulk storage, I'd use 2 disks as hot spares, and have 2 seperate RAID5 or 6 of 11 disks, then stripe those together so its raid 5+0 or 6+0. if this is for higher performance storage, I would build mirrors and stripe them (raid 1+0) re: alignment, use the whole disks, without partitioning. then there's no alignment issues. use a raid block size of like 32k. if you need multiple file systems, put the whole mess into a single LVM vg, and create your logical volumes in lvm. -- john r pierce N 37, W 122 santa cruz ca mid-left coast