disk bandwidth
- Stephen M. Rumble
Sequential bandwidth across an entire disk (ST3500514NS)
Random 8MB Segment bandwidth (ST3500514NS)
"Optimal" read/write bandwidths are 129.85MB/s and 130.5MB/s, respectively. This represents the best the disk can do anywhere, so they're really optimal numbers for the lowest sectors (outer-most tracks of the disk). Note that these are with write caching on, which increases sequential write bandwidth by about 10-15%.
Disk Range ??(first seg, last seg) |
Avg Read BW |
Read PCT Optimal |
Avg Write BW (wr cache on, off) |
Write PCT Optimal |
|---|---|---|---|---|
Whole disk (0-58000) |
87MB/s |
67% |
71.8MB/s, 85.7MB/s |
55%, 66% |
First half (0-29000) |
103.5MB/s |
79.7% |
80MB/s, 102.7MB/s |
61%, 79% |
First quarter (0-14500) |
107.9MB/s |
83.1% |
90.4MB/s, 107.6MB/s |
69%, 82% |
First 1GB (0-120) |
114.6MB/s |
88.3% |
102.7MB/s, 114MB/s |
79%, 87% |
Note that there appears to be a significant random access write penality when the disk write cache is enabled (hdparm -W1 /dev/foo).
Cluster Hard Disk Bandwidth August 2011 (rc01-rc60)
Putting this data up in case we plug our disks back in and want to see if performance has changed much over time.
Note 'rcXX-2' indicates the second disk. rc01-rc40 have a WD2503ABYX enterprise disk in the first slot and a desktop Seagate ST3500418AS in the second. rc41-rc60 have only WD disks (which is pretty obvious in the fans high graph).
Fans at normal speed (typical vibration):
Fans at highest speed:
