Hello,
I ahve problem under Linux with random periods of time WD MyBook 1TB 1012 has transfers rates about 3MB/s
and blocks any other read/writes attempts and aplications stop running while are waiting for IO.
This is also when PC is idle… it looks like there is some communication with MyBook and tried different kernels
and the same strange thing happends from time to time.
Nowadays, I’m using Fedora 12 with latest stable Linux kernel (customized by $ make oldconfig)
$ uname -a
Linux aslin 2.6.39.1-aslin_server #1 SMP Thu Jun 9 18:16:36 CEST 2011 x86_64 x86_64 x86_64 GNU/Linux
Below stats from period of time where no problems with WD MyBook 1TB-nice write transfer about 30MB/s.
dd if=/dev/zero of=zero.1gb bs=1024k count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 34.0652 s, 31.5 MB/s
dd if=/dev/zero of=zero.1gb bs=1024k count=512; sync
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 15.8287 s, 33.9 MB/s
Linux system monitoring tool “dstat” in 1 second periods reports good transfers (writes in 8th column).
Note, that I followed “sync” to try to flush data to this usb disk drive, because of system could cache this data
and flush later…
dstat
usr sys idl wai hiq siq| read writ| recv send| in out | int csw
0 0 0 100 0 0| 0 600k| 0 0 | 0 0 | 131 102
0 0 0 100 0 0| 0 0 | 0 0 | 0 0 | 99 46
0 0 0 100 0 0|8192B 4560k| 0 0 | 0 0 | 340 466
0 0 0 100 0 0| 0 0 | 0 0 | 0 0 | 96 49
0 0 0 100 0 0|4096B 872k| 0 0 | 0 0 | 138 140
0 2 0 98 0 0|4096B 2040k| 0 0 | 0 0 | 219 236
0 0 0 100 0 0| 0 0 | 0 0 | 0 0 | 84 42
0 0 0 100 0 0| 0 2880k| 173B 221B| 0 0 | 260 309
0 0 0 100 0 0| 0 0 | 76B 64B| 0 0 | 91 54
1 0 0 100 0 0| 0 2040k| 0 0 | 0 0 | 214 236
1 1 0 99 0 0| 0 2192k| 0 0 | 0 0 | 218 245
0 0 0 100 0 0| 0 0 | 0 0 | 0 0 | 94 46
1 0 0 100 0 0| 0 960k| 0 0 | 0 0 | 183 214
0 0 0 99 0 0| 0 1440k| 0 0 | 0 0 | 182 180
1 1 0 99 0 0| 0 2280k| 0 0 | 0 0 | 214 253
0 1 0 99 0 0| 0 10M| 0 0 | 0 0 | 626 967
0 2 0 97 0 1| 0 28M| 0 0 | 0 0 |1514 2590
0 1 0 98 0 1| 0 26M| 0 0 | 0 0 |1431 2434
0 3 0 96 0 1| 0 22M| 0 0 | 0 0 |1252 2071
0 2 0 98 0 0| 0 28M| 0 0 | 0 0 |1529 2619
0 3 0 96 0 2| 0 28M| 0 0 | 0 0 |1523 2589
1 2 0 96 0 1| 0 28M| 0 0 | 0 0 |1598 2751
1 3 0 94 0 3| 0 28M| 0 0 | 0 0 |1587 2716
0 1 0 98 0 0|4096B 16M| 0 0 | 0 0 | 910 1480
0 2 0 97 0 1| 0 28M| 0 0 | 0 0 |1527 2623
0 2 0 96 0 1| 0 28M| 0 0 | 0 0 |1525 2612
1 1 1 98 0 1| 0 28M| 0 0 | 0 0 |1689 2718
1 1 1 98 0 1| 0 24M| 0 0 | 0 0 |1551 2326
But, as mentioned above from time to time-have no idea why-even idle system has above 80% wait IO
and then write rates are below 5MB/s and there are no 25MB/s transfers, and what is much worse but could wait
if were able to use apllications without delays,but
system is UNUSABLE, and this very slow write operation hungs up system for several seconds-
when tried this 1GB write test followed by sync… had to try to break this command below by ctl-c , because
was not able to open any other file or write even smal ammout of data…
dd if=/dev/zero of=zero.1gb bs=1024k count=1024; sync
records in
565+0 records out
592445440 bytes (592 MB) copied, 151.356 s, 3.9 MB/s
Above had to ctl-c this operation, because of could do enything about move mouse cursor and switch windows-
!!! Looks like some system process (maybe “sync” sheduled by system from time to time, I guess)
tries AT ONCE write all cached data and there is no room for other reads or even small writes !!!
Also tried other IO schedulers by passing to linux kernel during boot:
elevator=deadline
and setting /dev/sda IO scheduler to other like default “cfq” “noop”
($ echo “noop” >/sys/block/sda/queue/scheduler )
and increasing number of requests ($ echo “1024” >/sys/block/sda/queue/nr_requests )
$ lsscsi
[0:0:0:0] disk WD My Book 1012 /dev/sda
[0:0:0:1] enclosu WD My Book Device 1012 -
But from time to time still this WD MyBook 1TB (only USB 2.0 port)
blocks system for several seconds…
Also disconnected other USB devices from PC (motherboard Asus M2A-VM $GB RAM).
Have no idea why this happends and why this IO write operations block read operations and make system
look like frozen for several seconds…
Regards.
Szan.