[Users] so, what do you want next in oVirt?

[Karli Sjöberg]

fre 2013-09-06 klockan 09:46 +0200 skrev NOC:


On 09/06/2013 08:11 AM, Karli Sjöberg wrote:
> What about swap? Don´t they have any swap file, or partition at all?
> Swap-file over NFS must suck quite badly, no? We have bought
> semi-cheap SSD's for our Hosts to use as swap to get more out of them
> from memory overprovisioning.

I don't quite see the point, unless you have mirrored ssd's. Data
corruption on ssd's is more frequent than on spinning disks and
disastrous when it happens in a swapped out page...


Yes they absolutely need to be mirrored. I disagree though that modern SSD's are more failure-prone than spinning disks. I would rather say that they about as failure-prone as any other disk:
http://www.tomshardware.com/reviews/ssd-reliability-failure-rate,2923-9.html

And if you know which one's to buy, and which ones to watch out for, they may even last you longer:
http://www.hardware-revolution.com/best-ssd-best-hdd-for-your-money-may-2013/



(And why not add
more RAM?)


Well, for us, it´s mainly since we are extremely budget-constraint, using old, worn out servers that can´t handle putting in that much RAM. Also older servers require older RAM, which in turn are harder- and more expensive- to come by.




But why use swap at all? I'm assuming you dimension a node to its
intended use, so I guess lots of memory and CPU cores (in our case
anyway) and you can allocate the available memory to the VMs until it's
finished. I don't see much need for swap there.

Perhaps my view is different than usual, I see swap as the gravelly
escape roads on steep hills for trucks/cars who have failing breaks. It
just reduces the damage in case of unexpected failures.


Is there a down-side to reduce damage in case of unexpected failures?:)



Swap isn't
something to use on a regular basis as cheep memory, as RAM is not that
expensive anymore and magnitudes faster.

/Simon



--

Med Vänliga Hälsningar
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Karli Sjöberg
Swedish University of Agricultural Sciences
Box 7079 (Visiting Address Kronåsvägen 8)
S-750 07 Uppsala, Sweden
Phone:  +46-(0)18-67 15 66
karli.sjoberg at slu.se<mailto:karli.sjoberg at adm.slu.se>
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