I am looking into performance issues we are having.
We currently have a 4 drive RAID5 (3+1 fail over) and read performance sucks.
Looking at RAID1 with 2 drives (maybe more, any benefit?) but from what I have read around, RAID1 with madam doesn't seem to give any more performance over reads than a single drive, eg it would split the reads over the 2 drives.
Is linux software RAID1 better performance than single drive?
Best Answer
Single-threaded application performance on mdadm RAID1 is indeed no better than using a single disk. That's because mdadm chooses one of the disks in the array to satisfy a given read request. So if your workload consists of a single process reading sequentially from a single file, then mdadm RAID1 will not outperform a single disk.
However, if your workload instead consists of many parallel file accesses---such as would occur in a file server being hit by multiple users at once---then RAID1 will be faster than a single disk because the concurrent read requests are allocated across multiple disk spindles.
In summary, whether or not mdadm RAID1 will be faster than a single disk depends a lot on your particular mix of workloads.