debian-user:
I had the need to zero-fill a Seagate Constellation ES.2 3 TB SATA
magnetic hard disk drive using an Intel DQ67SW motherboard, Intel Core
i7-2600S processor, 8 GB dual-channel memory, StarTech PEXSAT32 adapter,
and Debian:
2024-09-08 08:05:02 root@bullseye-bios
~/hardware/seagate/ST33000650NS/REDACTED
# cat /etc/debian_version ; uname -a
11.10
Linux bullseye-bios 5.10.0-32-amd64 #1 SMP Debian 5.10.223-1
(2024-08-10) x86_64 GNU/Linux
When done, I ran some benchmarks to compare sequential write performance
for various synchronization methods and block sizes:
1. Using dd(1) with option oflag=sync:
2024-09-08 09:19:27 dpchrist@laalaa ~/hardware/seagate/ST33000650NS/REDACTED
$ tail -n 214 log.txt | perl -pe 's/^\s+//' | egrep -A 3 'oflag=sync' |
egrep 'time|GiB'
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1G count=1
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.3181 s, 147 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256M count=4
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.39608 s, 145 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=64M count=16
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.48021 s, 144 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=16M count=64
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.92566 s, 135 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=4M count=256
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 8.97546 s, 120 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1M count=1K
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 15.3814 s, 69.8 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256K count=4K
oflag=sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 40.8931 s, 26.3 MB/s
2. Using dd(1) with sync(1):
2024-09-08 09:19:38 dpchrist@laalaa ~/hardware/seagate/ST33000650NS/REDACTED
$ tail -n 214 log.txt | perl -pe 's/^\s+//' | egrep -A 3 '&& sync' |
egrep 'time|GiB'
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1G count=1 && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.3975 s, 145 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256M count=4 && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.21795 s, 149 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=64M count=16 && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.21845 s, 149 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=16M count=64 && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.20049 s, 149 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=4M count=256 && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.11058 s, 151 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1M count=1K && sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.12372 s, 151 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256K count=4K &&
sync
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.10426 s, 151 MB/s
3. Using dd(1) without explicit synchronization:
2024-09-08 09:20:45 dpchrist@laalaa ~/hardware/seagate/ST33000650NS/REDACTED
$ tail -n 214 log.txt | perl -pe 's/^\s+//' | egrep -A 3 time | egrep
'time|GiB' | egrep -v -A 1 '(MB\/s|sync)$' | egrep -v '^--'
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1G count=1
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.30077 s, 147 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256M count=4
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.27323 s, 148 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=64M count=16
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.21564 s, 149 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=16M count=64
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.17308 s, 150 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_Z294MZFA bs=4M count=256
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.20907 s, 149 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=1M count=1K
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.11303 s, 151 MB/s
# time dd if=/dev/zero
of=/dev/disk/by-id/ata-SEAGATE_ST33000650NS_REDACTED bs=256K count=4K
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 7.13726 s, 150 MB/s
Additional observations:
1. The Bash shell 'time' built-in command and the per-second/
per-transfer performance values displayed by dd(1) option
'status=progress' can show the interaction between dd(1) option
'oflag=sync', kernel I/O buffering, dd(1) write completion, and sync(1).
2. dd(1) does not exit until the final block has been written.
Conclusions:
1. dd(1) option 'oflag=sync' causes block size to affect write
performance -- increasing the block size increases the performance. The
effect is non-linear, with a knee at around 30 IOPS. For best
performance, block size should be tuned to produce 30 IOPS or less.
2. sync(1) is unnecessary.
3. Use dd(1) as-is, without 'oflag=sync' or sync(1).
David
