# dd if=/dev/ad4 of=/dev/null bs=128k
This block size may be (very) slow, unless it's an old disk. Is there any good reason for that?wblock said:# dd if=/dev/ad4 of=/dev/null bs=128k
# zpool scrub
# zpool status
Beastie said:This block size may be (very) slow, unless it's an old disk.
% man dd | less +/sizes
Is there any good reason for that?
Yes, but what I meant is why are you not using bigger block sizes, such as 1m or so.wblock said:It's 128k, not 128.
% man dd | less +/sizes
Reading multiple blocks at a time greatly reduces overhead, making it much faster.
Beastie said:Yes, but what I meant is why are you not using bigger block sizes, such as 1m or so.
% time dd if=/dev/ada0 of=/dev/null bs=64k count=64k
65536+0 records in
65536+0 records out
4294967296 bytes transferred in 37.826251 secs (113544620 bytes/sec)
0.020u 0.873s 0:37.82 2.3% 29+1242k 65536+0io 0pf+0w
% time dd if=/dev/ada0 of=/dev/null bs=128k count=32k
32768+0 records in
32768+0 records out
4294967296 bytes transferred in 37.830190 secs (113532797 bytes/sec)
0.000u 0.684s 0:37.83 1.7% 27+1166k 32768+0io 0pf+0w
% time dd if=/dev/ada0 of=/dev/null bs=1m count=4k
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 37.838443 secs (113508034 bytes/sec)
0.000u 0.637s 0:37.83 1.6% 23+977k 32768+0io 0pf+0w
wblock said:Brute force:
# dd if=/dev/ad4 of=/dev/null bs=128k
Watch for errors. See also sysutils/smartmontools, although SMART has been known to report no problems on drives with known problems.