On Thu, 12 Jun 1997, Dave Hitz wrote:
In order for a RAID reconstruction to complete, you have to read all of the data on all of the other disks. So RAID reconstruction time is proportional the the amount of data, not proportional to the number of disks.
I noticed that even on an F220 with raid.reconstruct_speed set to 10, sysstat reports the CPU is only about 60% busy. Was this a conscious design decision, to reserve some CPU for its normal NFS duties? The disk write speed is barely 1MB/sec, so it shouldn't be a physical drive limitation. Is the SCSI bus saturated, perhaps?
In some cases it may be beneficial to have the NetApp just go all-out on rebuilding on a spare drive and forget about doing any NFS until it leaves degraded mode. I suppose this is another "hang-onself- with-enough-rope" issue. ;-)
f220> sysconfig -r RAID Disk DISK_ID# HA.SCSI# Used (MB/blks) Phys (MB/blks) --------- -------- -------- -------------- -------------- parity 0 0.0 4000/8192000 4095/8386728 data 1 1 0.1 4000/8192000 4095/8386728 data 2 2 0.2 4000/8192000 4095/8386728 data 3 3 0.3 4000/8192000 4095/8386728 data 4 10 0.5 4000/8192000 4095/8388312 data 5 9 0.4 4000/8192000 4095/8388312 data 6 8 0.6 4000/8192000 4095/8388312 data 7 7 9a.1 4000/8192000 4095/8388312 (reconstructing, 1% done) data 8 6 9a.2 4000/8192000 4095/8388312 data 9 4 9a.0 4000/8192000 4095/8388312 f220> sysstat 1 CPU NFS CIFS HTTP Net kb/s Disk kb/s Tape kb/s Cache in out read write read write age 53% 0 0 0 0 0 9216 992 0 0 >60 54% 0 0 0 0 0 8928 992 0 0 >60 59% 0 0 0 0 0 8928 1024 0 0 >60 58% 0 0 0 0 0 8928 960 0 0 >60 60% 0 0 0 0 0 8928 992 0 0 >60 61% 0 0 0 0 0 8928 1024 0 0 >60 61% 0 0 0 0 0 8208 1024 0 0 >60 55% 0 0 0 0 0 8928 992 0 0 >60 62% 0 0 0 0 0 9216 992 0 0 >60