Udo Kaune schrieb am 21.04.23 um 18:59:
Am 21.04.23 um 16:59 schrieb Dr. Thorsten Brandau:
PS: Despooling seems unusually slow to me.
PPS: Please do not top-post.
I have noticed that both, spooling and despooling is very slow. I
have no idea why, the disc makes easily 300 MB/s and there is nothing
else going on on that raid.
I have no idea where to even look. When I start parallel other
processes, they can use the full power. iotop goes up to 300 MB/s
from time to time to drop then again to zero.
On another server where I go directly disc to tape it is faster (LTO-6).
Is your tape block size set to zero?
mt -f /dev/nst0 status | grep size
mt -f /dev/nst0 defblksize 0
mt -f /dev/nst0 setblk 0
It is set to 0
Tape block size0 bytes. Density code 0x60 (no translation).
Grab an empty tape and make some test:
Nothing will be faster than this:
# ddrescue -s 128G --force /dev/zero /dev/null
GNU ddrescue 1.21
Press Ctrl-C to interrupt
ipos: 127999 MB, non-trimmed: 0 B, current rate: 7029 MB/s
opos: 127999 MB, non-scraped: 0 B, average rate: 11636 MB/s
non-tried: 0 B, errsize: 0 B, run time: 11s
rescued: 128000 MB, errors: 0, remaining time: n/a
percent rescued: 100.00% time since last successful read: 0s
Finished
dd_rescue: (info): Summary for /dev/zero -> /dev/null
dd_rescue: (info): ipos:8226443904.0k, opos:8226443904.0k,
xferd:8092226176.0k
errs: 0, errxfer: 0.0k,
succxfer:8092226176.0k
+curr.rate:651293248kB/s, avg.rate:644669888kB/s, avg.load:
99.9%
How fast can we write to the disk (ever)?
# ddrescue -D -s 128G --force /dev/zero test.bin
GNU ddrescue 1.21
Press Ctrl-C to interrupt
ipos: 127999 MB, non-trimmed: 0 B, current rate: 228 MB/s
opos: 127999 MB, non-scraped: 0 B, average rate: 727 MB/s
non-tried: 0 B, errsize: 0 B, run time: 2m 56s
rescued: 128000 MB, errors: 0, remaining time: n/a
percent rescued: 100.00% time since last successful read: 0s
Finished
dd_rescue: (info): Summary for /dev/zero -> test.bin
dd_rescue: (info): ipos: 150554240.0k, opos: 150554240.0k, xferd:
16336512.0k
errs: 0, errxfer: 0.0k, succxfer:
16336512.0k
+curr.rate: 1542715kB/s, avg.rate: 964700kB/s, avg.load:
15.2%
=-........................................< 0% TOT:
0:00:17
(it does not write 128GB but does not find an end here - so I stopped it)
How fast can we read from the disk (ever)?
# ddrescue -d --force test.bin /dev/null
GNU ddrescue 1.21
Press Ctrl-C to interrupt
ipos: 134217 MB, non-trimmed: 0 B, current rate: 941 MB/s
opos: 134217 MB, non-scraped: 0 B, average rate: 986 MB/s
non-tried: 0 B, errsize: 0 B, run time: 2m 16s
rescued: 134217 MB, errors: 0, remaining time: n/a
percent rescued: 100.00% time since last successful read: 0s
Finished
dd_rescue: (info): test.bin is sparse (38%) , consider -a
dd_rescue: (info): expect to copy 351071360.0kiB from test.bin
dd_rescue: (info): ipos: 350896128.0k, opos: 350896128.0k, xferd:
350896128.0k
errs: 0, errxfer: 0.0k, succxfer:
350896128.0k
+curr.rate: 2124665kB/s, avg.rate: 1156943kB/s, avg.load:
7.9%
>----------------------------------------.< 99% ETA:
0:00:00
dd_rescue: (info): read test.bin (351071360.0kiB): EOF
dd_rescue: (info): Summary for test.bin -> /dev/null
dd_rescue: (info): ipos: 351071360.0k, opos: 351071360.0k, xferd:
351071360.0k
errs: 0, errxfer: 0.0k, succxfer:
351071360.0k
+curr.rate: 2136854kB/s, avg.rate: 1157213kB/s, avg.load:
7.9%
>-----------------------------------------< 100% TOT:
0:05:03
Lets generate a binary random file which is merely incompressible
# ddrescue -s 128G --force /dev/urandom test.bin
GNU ddrescue 1.21
Press Ctrl-C to interrupt
ipos: 127999 MB, non-trimmed: 0 B, current rate: 43843 kB/s
opos: 127999 MB, non-scraped: 0 B, average rate: 171 MB/s
non-tried: 0 B, errsize: 0 B, run time: 12m 27s
rescued: 128000 MB, errors: 0, remaining time: n/a
percent rescued: 100.00% time since last successful read: 0s
Finished
dd_rescue: (info): Summary for /dev/urandom -> test.bin
dd_rescue: (info): ipos: 140804864.0k, opos: 140804864.0k, xferd:
6587136.0k
errs: 0, errxfer: 0.0k, succxfer:
6587136.0k
+curr.rate: 238426kB/s, avg.rate: 306436kB/s, avg.load: 99.9%
=-........................................< 0% TOT:
0:00:21
It looks fitting to other services like Rsync. I am running on an
external RAID6, so I assume the discs and caching is just low, as I have
several file storages >80TB on that device. No SSD or so.
Initially I tested the drive with about 400MB/s, so that fits around the
maximum read speed of the discs coming from the raid.
Are there any tweaking parameters I could try?
Cheers
TB
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