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Why does my sequential speed differ so much?

XigmaNAS Basic Tune-up
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Why does my sequential speed differ so much?


Post by superapan »

Hi there, new user of NAS4Free. I have tried the competition, but I get better speeds, and this is so much cleaner and much less bloated. I even donated! :)

Anyways, I have a question. If I transfer an ISO file between ZFS datasets shared with CIFS, I easily saturate my gigabit network at 110+ MB/s. If I transfer an .mkv file, the speed flucturates between 30-60 MB/s. Why is this? Are they not both just simple sequential reads and writes?

Any insight is greatly appreciated.
HP ProLiant MicroServer Gen8 | Intel Xeon E3-1265Lv2 | 16 GB ECC RAM | IBM M1015 (IT) | ESXi 6.0

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Re: Why does my sequential speed differ so much?


Post by Parkcomm »

I'm going to guess, based on no evidence is the level of fragmentation (the more recent and/or the larger file will probably have more fragmentation). Fragmentation means random reads/writes.

Another reason could be the amount of data in the ARC as opposed to on disk.
NAS4Free Embedded - Prester (revision 2003), HP N40L Microserver (AMD Turion) with modified BIOS, ZFS Mirror 4 x WD Red + L2ARC 128M Apple SSD, 10G ECC Ram, Intel 1G CT NIC + inbuilt broadcom

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