<office@xxxxxxxxxxx> writes:
> I would like to know your opinion on the viability of a SW RAID 1 powered
> Xen node. The CPU is a i7-920 Quad core, 2.66Ghz, 8MB cache and 8GB of RAM.
> The 2 HDDs are absolutely normal (no raptor, 10k-15k etc - just normal
> SATA) and there's no HW RAID. I was thinking to allocate some 70% of the
> resources to VEs and the rest to the node itself.
Yes. I did fairly extensive tests on hw vs software raid 1 and 1+0
and even with a battery backed cache (only 64MiB at the time, this
was a few years back) the hw raid was slightly slower than the
linux MD raid. It was about the same.
Now, with a larger (and battery-backed) cache and raid5 or 6 rather
than raid 1 or 1+0, the story may be different, but if you only
have two spindles, in my opinion, it's better to spend the money
on more spindles.
Me, all my servers have 8 cores (a single 2.0ghz G34 opteron)
32GiB of registered ecc ram and 4 "enterprise" sata disks in a 1+0
linux MD raid.
The big thing you've gotta watch for are people who use a bunch
of disk IO. even one guest can make I/O suck for a lot of people
(and when I have better tools for doing that, I'll post them here.
Ideas are appreciated.)
but overall, my system seems to work fairly well, even when I put 31GiB
worth of 512MiB, 256MiB, 128MiB and 64MiB guests on the same host.
I/O does suck, but I don't think we're going to get around that
without spending a whole lot on a raid card.
I have been looking at bcache[1]... when it's done, it will be
pretty awesome, but I don't know how "done" it is just yet.
[1]http://bcache.evilpiepirate.org/
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