In my system I am running a few virtual systems, currently they reside in raw files. Initially I created a raid1 partition, with an ext4 file system on top of the whole partition. /dev/md/md85 from /dev/sda5 /dev/sdb5 mirror 120G However I know from experience that raw files can be a bit slow (totally different setup, raid6), so I wondered about the possibility of creating 3 individual partitions on top of the raid and if this would improve performance. Having read the man, it seems that partitions on top of raid are fine, and no special options are required in the raid creation. Now the questions. Alignment... Now I understand that the base disk partitions require alignment based on the drive... and I assume mdadm then creates its internal structure so that it is also aligned, or does it? My wondering here is that I know mdadm has an area that holds data bout the raid, then another area that holds the data... if the data area (chunks? I may have the wrong term) was not aligned to the underlying drives then would a write of "chunkX" potentially partially write to disk area62 and disk area63 (for example) causing the underlying disk to do a RMR. If we assume that raid/base disk is all hunky dory alignment wise, this then brings me on to partitions on top of the raid... As raid when partitioned pretends to be a block disk device; when I used gdisk to look at it without performing anything except a look at its layout it reports its a normal disk, 512bytes, first usable sector 34, partitions will be aligned on 2048 sector boundaries. So my question is am I correct in thinking that "md85 partition 01" will align to (an imaginary) 2048 boundary on "md85" which will align to the real 2048 boundary on "sda5/sdb5"? I may just stick with raw files but as I am in the process of upgrading it piqued my interest and might be worth converting to partitions, or possibly LVM which seems the preferred or most documented option (bit I'm not sure I want to add a whole new set of skills and learning curve at the moment). My intention is to add 2 more disks to the mirror raid, which while not changing the write performance I believe will improve the read performance... at least as far as I can tell, again is this assumption correct? Thanks in advance. Jon. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
