Re: [MooseFS-Users] changelogs: Writes per day

[Gandalf C. <gan...@gm...>]

Il giorno gio 7 giu 2018 alle ore 18:08 Zlatko Čalušić
<zca...@bi...> ha scritto:
>
> Hello Gandalf,

Hi

> That is just impossible to answer without knowing your workload + your
> parameters (noatime mounts or not?). You're the only one that can see
> that for yourself and decide appropriately. You can never go wrong with
>  >1 DPWD datacenter grade SSD, becuase you always get what you paid for.

I know that would be impossible, but it's also impossible to forecast
metadata operations
in a brand new cluster.

That's why I've asked. If, on heavy cluster, maybe with hundreds of
VMs or a lot of maildirs
(that should do metadata operation more than VMs), an average is more
or less 100GB per day,
any enterprise-grade SSD (even the read-intensive) would be ok.

On the other hand, if that cluster is making 1 TB per day, I'll be
better to buy a write-intensive SSD
or a much bigger read-intesive SSD

Anyway, the disk space requirements shown in the following formula:
SPACE = RAM * (BACK META KEEP PREVIOUS + 2) + 1 * (BACK LOGS + 1)

talks about "RAM". Is "RAM" the current metadata usage or the server RAM ?

In example, If I have a master server with 64GB ram but i'm only using
2GB for metadata, the space requirement
is evaluated by using "2GB" or "64GB" ? There is a lot of difference
in needed space and in costs (when using datacenter grade SSDs)