ZFS write speed

[Stefan Bethke]

Am 27.10.2010 um 22:51 schrieb S.N.Grigoriev:

> Hi list,
> 
> I've got very low write speed using ZFS on a SATA disk.
> My HDD configuration is:
> ad4: 70911MB <WDC WD740BLFS-01YBU0 04.04V01> at ata2-master UDMA100 SATA 3Gb/s
> ad6: 78532MB <Hitachi HDS728080PLA380 PF2OA60A> at ata3-master UDMA100 SATA 1.5Gb/s
> ad8: 1430799MB <WDC WD15EARS-00MVWB0 51.0AB51> at ata4-master UDMA100 SATA 3Gb/s

The EARS has 4k sectors, if I'm not mistaken.  I don't recall the eventual outcome, but there was a long thread on stable or hackers on how to ensure proper alignment and (minimun) 4k-sized writes to make sure the disk doesn't have to do a read-modify-write cycle, so try and search the archives.

> ad4 and ad6 are single-slice disks (UFS2 with soft updates)
> 
> ZFS configuration is following:
> zpool create Z ad8
> zfs create Z/music
> zfs create Z/video
> All ZFS parameters are default.
> kern.maxvnodes = 1000000
> 
> To test my configuration I recursively copied from ad6 to ad8 two directories.
> The first one contains MP3 files (average size = 10MB).
> The second one contains AVI files (average size = 1GB). 
> 
> To compare performance I repeated above tests with ad8 using UFS2 with soft updates.
> 
> 18GB of MP3 files required 10m35s to copy to UFS2 and 21m40s to copy to ZFS.
> 30GB of AVI files required 16m6s to copy to UFS2 and 1h2m39s to copy to ZFS.
> 
> I used for tests FreeBSD 8.1R amd64. Amount of RAM on my machine is 6GB.
> 
> Any tips?
> 
> -- 
> Regards,
> Serguey.
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-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811