Date: Mon, 05 Feb 2007 09:23:20 +0100 From: Indigo <indigo@voda.cz> To: "questions@freebsd.org" <questions@freebsd.org> Subject: Re: Dumb filesystem idea Message-ID: <op.tm9n86r95sheu4@spyro.eiecon.net> In-Reply-To: <op.tm9n571w5sheu4@spyro.eiecon.net> References: <op.tm8veaqj5sheu4@spyro.eiecon.net> <df9ac37c0702042123i45d9d66ajcfd29f10647d0101@mail.gmail.com> <op.tm9n571w5sheu4@spyro.eiecon.net>
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> On 2/4/07, Indigo <indigo@voda.cz> wrote: >> Hello Everyone, >> Im about to try a disklayout experiment and I wanted to ask everyone >> if >> Im trying things that are pointless or if I should extend the experiment >> somehow. >> >> Hardware: >> Highpoint RocketRAID 2320 >> 2xWD Raptor 74GB >> 5xWD Caviar 320GB >> >> Original idea for the setup: >> 74GB RAID1 (Raptors) >> /,/var,/usr >> 50GB RAID0 (Caviars[10GB from each - maybe less]) >> swap,/usr/obj,/tmp,[/var/audit] >> 1TB+ RAID5 (Caviars[the rest]) >> /home (or just general storage) >> >> The goal is to waste as few fast/reliable space as possible on things >> that >> CAN be lost and to generally reorganize the filesystem by file purpose. > > It looks to me like you are wasting system drive channels. That is, > IDE can only have two drives per channel, SATA can have one drive per > channel. SCSI is too expensive to waste on 10GB drives. So while you > might be moving low-use data off of a high-use file system you are > losing the ability to have a high-capacicy file system. > >> Known issue is that I'll need some script to recreate the RAID0 >> filesystems when they crash. > > Shouldn't be a prolem with gvinum. Except that some applications > /will/ crash if /tmp dissipears, and you certainly don't want swap to > dissipear if it's being used either. > >> Am I onto something here? I feel like running in circles - it's dumb to >> put /var/obj on the RAID1 where it just eats valuable space. But it's >> also >> dumb to put things on a RAID0 where they will crash a running system in >> the event of disk failure. I know my idea won't work but I wanted to ask >> if anyone was playing with similar ideas. > > The trick is to balance your performance requirements and your fault > tolerance with the data usage and system security requirements. The > fault tolerance of RAID 1 and RAID 5 are nearly the same, each can > survice exactly one drive failure. In your example above, the Raptor's > are fast, but depending on what the system is used for you might need > that speed in /var, swap, or some other mount point, most of the time > IO on / and /usr is pretty low. On the other hard, RAID 5 is fine for > a file server, but if you have a database on that volume you might > want to go with RAID 10. > > So no, your idea isn't dumb, you just didn't give enough information > to make a meaningful assessment. > Some more detail then: The HighPoint card is very decent, it can make the whole setup I described appear as three SCSI disks (da0-2). Ill make one slice on each and then partition those slices as I described. So FreeBSD will only see 3 SCSI disks(74GB,50GB,1TB) it shouldn't see the original SATA disks like it does with on-board controllers. da0s1a / da0s1d /var [mail] da0s1e /usr [homes,databases,htdocs] da1s1b swap da1s1d /usr/obj da1s1e /tmp da2s1d /usr/store [public storage/fileserver] Does anyone know how the system will react to da1 failing? Thanks, Vasek
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