0.7MiB/s, is this slow scan rate normal for a single 5400rpm hard disk?

Hi there,

I started using syncthing yesterday and currently at the process of completing the initial scan of my 2.7TB of data, from a single SATA 5400rpm hard disk.

My setup: OmniOS VM running on ESXi host, the physical 5400rpm SATA hard disk is connected to a LSI2008 HBA card that is pass-through’ed from ESXi to OmniOS. This hard disk forms a single disk zfs pool in OmniOS.

OmniOS has been given 4 vCPUs and 48GB of RAM.

I have seen extremely slow scanning speed from this hard disk. From the syncthing log, it shows:

    2020-05-28 09:13:31 real to hash: Setup/BTW_hlp.chm
    2020-05-28 09:13:31 Walk oeit5-ptrea [] current progress 136619995756/2488826695378 at 0.7 MiB/s (5%)
    2020-05-28 09:13:33 Walk oeit5-ptrea [] current progress 136620126828/2488826695378 at 0.7 MiB/s (5%)
    2020-05-28 09:13:35 Walk oeit5-ptrea [] current progress 136621175404/2488826695378 at 0.7 MiB/s (5%)
    2020-05-28 09:13:36 real to hash: Setup/btrez.dll
    2020-05-28 09:13:37 real to hash: Setup/btw_hlp.chm
    2020-05-28 09:13:37 Walk oeit5-ptrea [] current progress 136623608591/2488826695378 at 0.7 MiB/s (5%)
    2020-05-28 09:13:39 Walk oeit5-ptrea [] current progress 136623739663/2488826695378 at 0.7 MiB/s (5%)
    2020-05-28 09:13:41 Walk oeit5-ptrea [] current progress 136624132879/2488826695378 at 0.7 MiB/s (5%)

I understand the scanning and hashing tax processor and hard disk heavily. I have checked and can confirmed the bottleneck appears to be the hard disk. As there is next to nothing activities happening to the processor, but the disk utilisation is 100% all the time.

Below is the iostat output:

iostat -xtc tank sd2 5
                 extended device statistics                    tty         cpu
device    r/s    w/s   kr/s   kw/s wait actv  svc_t  %w  %b  tin tout  us sy dt id
tank     26.9    8.3 3167.9  489.4 74.6  4.6 2246.4  96 100    0    4   1  1  0 98
sd2      27.0   10.3 3169.5  489.6  0.0  4.6  124.0   0 100
                 extended device statistics                    tty         cpu
device    r/s    w/s   kr/s   kw/s wait actv  svc_t  %w  %b  tin tout  us sy dt id
tank      3.4    1.8  390.4   83.0 75.5  4.4 15395.5 100 100    0   87   0  1  0 99
sd2       3.4    2.4  390.4   83.0  0.0  4.4  767.4   0 100
                 extended device statistics                    tty         cpu
device    r/s    w/s   kr/s   kw/s wait actv  svc_t  %w  %b  tin tout  us sy dt id
tank     18.0    3.4 2284.6  190.8 75.1  5.7 3768.6 100 100    0   62   0  1  0 99
sd2      18.0    4.2 2284.6  190.8  0.0  5.7  256.3   0 100

My question is: Is this normal for a 5400rpm hard disk, hashing at 0.7Mbps? Note that I have done some benchmarking on this hard disk, it can easily saturate 1Gbps network when doing read from another server, from the same zfs pool.

Thanks.

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