[arch-general] mdadm: RAID-5 performance sucks
karol at babioch.de
Wed Apr 10 08:18:27 EDT 2013
I guess I was too vague with some of the details regarding the setup, so
I will try to be more specific now.
Am 09.04.2013 18:20, schrieb Chris Down:
> I assume you're using Linux software RAID
> I've experienced this when using RAID6 and a suboptimal stripe cache
I already have tinkered with the stripe cache size, but probably should
approach this more systematically. I've found a "tuning" script at ,
but although it increased performance on Ubuntu by a bit, it hadn't any
impact on Arch :(.
Am 10.04.2013 02:35, schrieb Rafa Griman:
> What filesystem?
> What "benchmark" are you running?
Simple and plain "old" dd, just as described at .
> Stripe size?
In both cases the chunk size is 512K, which is quite big, but it is
primarily used for video files and works with Ubuntu just fine.
> HDDs connected to a PCI(e|X) RAID controller or on board controller?
Its an onboard controller. To be more specific, this is what lspci says:
00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset
Family SATA AHCI Controller (rev 05)
> Those 70 MB/s and 35 MB/s are from a client node or local?
I've measured them in both cases (Arch & Ubuntu) locally, but from a
client I get very similar results.
> If they're from a client node, what are you using: FTP, SAMBA, NFS, ...?
I've only tried SMB so far, but given the fact that the results are bad
as they are locally, it shouldn't matter here.
> Config files?
Which ones? Pretty much everything is measured out of the box, partially
even using the live environments, so I haven't configured too much at
all. As said I've played around with the sysctl settings, but haven't
configured anything else that should matter here.
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