Partitioning scheme ideas
dom at helenmarks.co.uk
Thu Apr 19 10:30:10 BST 2007
On Thu, 19 Apr 2007 10:04:41 +0100 (BST)
Robert Watson <rwatson at FreeBSD.org> wrote:
Robert & Richard, many thanks for taking the time to reply.
> On Thu, 12 Apr 2007, Dominic Marks wrote:
> > With that in mind I have purchased a box with four hot-swap drives and a 3
> > year parts+labour warranty from HP. I also have an iLO unit installed. So
> > far so good.
> I have two server boxes in the US and live in the UK, and had similar
> long-term concerns. Other than the normal redundant drives and power supplies
> (i.e., moving parts), the main concerns are proper software configuration and
> remote console/power access if needed. I've been very impressed with iLo on
> the HP hardware I've used in the past, and recommend it highly. I'm much less
> impressed with the lower end generic remote management parts in cheaper HP
> hardware, where the BIOS's tend to contain incorrect information, you get
> stuck with serial-over-lan, etc.
Well, I'm optimistic I will have avoided that. It is certainly
branded as iLO so if I have been sold some cheaper rubbish then
I will not be a happy man!
> > As I've said I have four 80GB SATA drives (the Businesses data capacity
> > requirements are not that great).
> > My current plan is to put the system (OS & Applications) on to a small
> > mirror which is spread over all four drives. This should give me the
> > absolute maximum level of protection and not waste much space either.
> > Looking at the existing system (which is being replaced) 4GB would be more
> > than sufficient for / and /usr/local. The number of installed applications
> > will be constant for the life time of the system so I am not risking much
> > here.
> Sometimes people make the mistake of not putting swap on the RAID. Don't make
> that mistake. :-)
Indeed. Just after I sent the initial message it occurred to me
that I should have mentioned I would be doing mirrored swap too.
> > The remaining disc space is used by only two other things. Samba file shares
> > (~30GB) and E-Mail (~15GB). To get a good balance for these I could go with
> > two, two drive RAID1 mirrors, or one, four drive RAID10. I don't have
> > hardware RAID5 available, I'm not using geom_raid3 again (that is in use at
> > the moment and its really, really slow) and I haven't played with the
> > experimental graid5 module.
> I think it's all about the number of failures you want to tolerate. For
> long-haul survival of the system where over-committing resources isn't a
> problem, a mirror with many replicas seems like a pretty good model. There
> have been varying opinions expressed over time regarding hot spares and I'm
> not sure whether the current wisdom is to leave the drive idle and use it as a
> rebuild target after a failure of one of the online drives, or simply to have
> all drives online all the time.
>From what I have read recently, specifically Google's disc
audit report, it seems that disc activity has little or no
bearing on life time. Which makes hot spares a luxury I can
live without. Certainly this has been the case in my
> > I've briefly flirted with the idea of running CURRENT on it to get ZFS and
> > making use of it for this, but when it is a remote system which (will not be
> > redundant) I shied away from it. Especially so after being on the
> > zfs-discuss mailing list where there quite a few people posting about
> > corruption and panics in Solaris ZFS.
> While ZFS looks like it will be excellent technology to use in this scenario
> in the future (with nice properties like being able to set the level of
> replication per volume, and error detection/healing), it's definitely
> experimental on both Solaris and FreeBSD. I would not deploy it in production
> at this point for systems I'm unable to tolerate partial or complete failure
> for. Maybe in six to twelve months with 7.1 out the door, it will be a less
> risky proposition.
I'm sure all FreeBSD users are chomping at the bit for
7.0-RELEASE now! I know I am.
> > So, any thing obviously wrong, anything I haven't considered? The entire
> > data set is backed up off-site on a nightly basis and the system will be
> > protected with a UPS. I have roughly two weeks before I start the build.
> iLo should address both the remote power and remote console concerns. Get
> your partitioning right up front, and do set up enough swap so you can get a
> crash dump if you need to. Make sure you always keep a /boot/kernel.good
> around so you can back out remote kernel upgrades, and you might consider
> keeping a spare /rescue.good around in case you need to recover. If you
> configure a firewall to "default to deny", consider also keeping a
> kernel.good.GENERIC in your / so you can boot a kernel without the firewall in
> the event you need to pull down replacement files over the network after a bad
> upgrade. While that's a pretty unlikely scenario, in the event it happens
> it's a lot easier to do that than try to figure out how to get the files onto
> the disk without network access :-).
I have experienced this particular level of hell before,
several times. It is even less fun when you don't have a
remote console and the system is not in co-location.
Luckily for this project a firewall will not be required.
> Finally, consider how you're going to handle backups -- remote backups are a
> pain to deal with if your data size substantially exceeds available bandwidth.
> Some colocation centers provide backup facilities, but usually at significant
> cost. With modern broadband and a relatively small data size, perhaps you're
> fine with backing up over the network; in my case I storage 1/3TB of e-mail on
> one of the remote servers, and that makes things a bit more tricky :-).
I am fortunate to have high-bandwidth connections at both ends
- and rsync is a miracle worker!
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