Re: Storage server
Am Samstag, 8. September 2012 schrieb Veljko:
> On Fri, Sep 07, 2012 at 01:26:13PM -0500, Stan Hoeppner wrote:
> > On 9/7/2012 11:29 AM, Veljko wrote:
> > > I'm in the process of making new backup server, so I'm thinking of
> > > best way of doing it. I have 4 3TB disks and I'm thinking of
> > > puting them in software RAID10.
> >
> > ["what if" stream of consciousness rambling snipped for brevity]
> >
> > > What do you think of this setup? Good sides? Bad sides of this
> > > approach?
> >
> > Applying the brakes...
> >
> > As with many tech geeks with too much enthusiasm for various tools
> > and not enough common sense and seasoning, you've made the mistake
> > of approaching this backwards. Always start here:
> >
> > 1. What are the requirements of the workload?
> > 2. What is my budget and implementation date?
> > 3. How can I accomplish #1 given #2 with the
> > 4. Least complexity and
> > 5. Highest reliability and
> > 6. Easiest recovery if the system fails?
> >
> > You've described a dozen or so overly complex technical means to some
> > end that tend to violate #4 through #6.
> >
> > Slow down, catch your breath, and simply describe #1 and #2. We'll
> > go from there.
>
> Well, it did sound a little to complex and that is why I posted to this
> list, hoping to hear some other opinions.
>
> 1. This machine will be used for
> a) backup (backup server for several dedicated (mainly) web servers).
> It will contain incremental backups, so only first running will take
> a lot of time, rsnapshot will latter download only changed/added files
> and will run from cron every day. Files that will be added later are
> around 1-10 MB in size. I expect ~20 GB daily, but that number can
> grow. Some files fill be deleted, other will be added.
For rsnapshot in my experience you need monitoring cause if it fails it
just complains to its log file and even just puts the rsync error code
without the actual error message there last I checked.
Let monitoring check whether daily.0 is not older than 24 hours.
Did you consider putting those webservers into some bigger virtualization
host and then let them use NFS exports for central storage provided by
some server(s) that are freed by this? You may even free up a dedicated
machine for monitoring and another one for the backup ;).
But well any advice depends highly on the workload, so this is just guess
work.
> Dedicated servers that will be backed up are ~500GB in size.
How many are they?
> b) monitoring (Icinga or Zabbix) of dedicated servers.
Then who monitors the backup? It ideally should be a different server than
this multi-purpose-do-everything-and-feed-the-dog machine your are talking
about.
> c) file sharing for employees (mainly small text files). I don't
> expect this to be resource hog.
Another completely different workload.
Where do you intend the backup for these files? I obviously wouldn´t put it
on the same machine as the fileserver.
See how mixing lots of stuff into one machine makes things complicated?
You may spare some hardware costs. But IMHO thats easily offset by higher
maintenance costs as well at higher risk of service outage and the costs
it causes.
> d) Since there is enough space (for now), and machine have four cores
> and 4GB RAM (that can be easily increased), I figured I can use it
> for test virtual machines. I usually work with 300MB virtual machines
> and no intensive load. Just testing some software.
4 GiB RAM of RAM for a virtualization host that also does backup and
fileservices? You aren´t kidding me, are you? If using KVM I at least
suggest to activate kernel same page merging.
Fast storage also depends on cache memory, which the machine will lack if
you fill it with virtual machines.
And yes as explained already yet another different workload.
Even this ThinkPad T520 has more RAM, 8 GiB, and I just occasionaly fire up
some virtual machines.
> 2. There is no fixed implementation date, but I'm expected to start
> working on it. Sooner the better, but no dead lines.
> Equipment I have to work with is desktop class machine: Athlon X4,
> 4GB RAM and 4 3TB Seagate ST3000DM001 7200rpm. Server will be in my
> office and will perform backup over internet. I do have APC UPS to
> power off machine in case of power loss (apcupsd will take care of
> that).
Server based loads on a desktop class machine and possibly desktop class
harddrives - didn´t look these up so if there are enterprise based ones
with extended warranty ignore my statement regarding them?
> In next few months it is expected that size of files on dedicated
> servers will grow and it case that really happen I'd like to be able to
> expand this system. Hardware RAID controllers are expensive and
> managers always want to go with least expenses possible, so I'm stuck
> with software RAID only.
Well extension of RAID needs some thinking ahead. While you can just add
disks to add capacity – not redundancy – into an existing RAID the risks
of a non recoverable failure of the RAID increases. How do you intend to
grow the RAID? And to what maximum size?
At least you do not intend to use RAID-5 or something like that. See
http://baarf.com
> But, one of dedicated server is slowly running out of space, so I don't
> think they will go for cheapest option there. I'll have to take care of
> that too, but first things first.
So the customer is willing to use dedicated servers for different web sites
and other services, but more than one machine for the workloads you
described above is too much?
Sorry, I do not get this.
Serious and honest consulting here IMHO includes exposing the risks of
such a setup in an absolutely clear to comprehend way to those managers.
Are these managers willing to probably loose the backup and face a several
day downtime of fileserver, backup and monitoring services in case of a
failure of this desktop class machine?
If so, if I would be in the position to say no, I would just say "no
thanks, search yourself a different idiot for setting up such an insane
setup". I understand, you probably do not feel yourself being in that
position…
> And, of course, thanks for your time and valuable advices, Stan, I've
> read some of your previous posts on this list and know you're storage
> guru.
It wasn´t Stan who wrote the mail you replied to here, but yes I think I
can learn a lot from him regarding storage setups, too.
I would love to learn more about those really big XFS installations and
how there were made. I never dealt with more than about 4 TiB big XFS
setups.
I read and write in these mailinglists to learn new stuff.
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
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