Date: Thu, 24 Nov 2011 14:29:41 -0500 From: APseudoUtopia <apseudoutopia@gmail.com> To: Matthew Seaman <m.seaman@infracaninophile.co.uk> Cc: freebsd-questions@freebsd.org Subject: Re: Setting up ZFS - Filesystem Properties and Installing on Root Message-ID: <CAKOHg=PxYFJC2uOD04%2BaxHUziaxXofU-qfyvS_Xm-NqNnWtCSw@mail.gmail.com> In-Reply-To: <4ECE9A7F.9000107@infracaninophile.co.uk> References: <CAKOHg=PEqeMPN_2dfQ%2B4msi1j7CMUu=iO%2BpSuezRoa_CELzQtw@mail.gmail.com> <88f3d8e819b3420f8e61723bee90ba5e.squirrel@www.magehandbook.com> <CAKOHg=N4yt0vdac8aZMUTK%2B8EnoSwxhK%2ByWmy7MsOXvKrWEmyw@mail.gmail.com> <4ECB580E.20203@infracaninophile.co.uk> <CAKOHg=PWcpqHdyvaS%2BoRwghA5m-A-rMxF-wqw3ZAPERzmO%2BpRw@mail.gmail.com> <4ECE9A7F.9000107@infracaninophile.co.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Nov 24, 2011 at 2:26 PM, Matthew Seaman <m.seaman@infracaninophile.co.uk> wrote: > On 24/11/2011 19:19, APseudoUtopia wrote: >> On Tue, Nov 22, 2011 at 3:06 AM, Matthew Seaman >> <m.seaman@infracaninophile.co.uk> wrote: >>> On 22/11/2011 02:09, APseudoUtopia wrote: >>>> Another quick question about swap: If I have 4 drives, with 512MB >>>> swap, the system uses all 4 swap partitions, correct? So it's not like >>>> it'd be going to waste? I'd have a total of 2 GB swap? >>> >>> Well, yes. =C2=A0If you just declare those raw partitions to be swap ar= eas, >>> that will be the case. =C2=A0However, doing this is asking for trouble:= you >>> subvert any resilience features obtained by using ZFS with raidz1. =C2= =A0If >>> any one of the drives fails, your swap area will break and your system >>> will probably crash. >>> >>> Better to set up two pairs of gmirrors for swap -- the procedure is >>> described here: http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/Mirror >>> in section3 "Finish Install." =C2=A0This will effectively give you a ra= id10 >>> for your swap, with a total size of 1GB. >>> >> >> I'm not sure I understand this. How would that negatively affect the >> raidz1? The swap isn't in the zpool. I understand the system may crash >> if the OS was using the swap space and the drive failed. But would you >> not be able to reboot into a degraded zpool state and still have a >> usable system? >> > > No -- it means a failed disk can cause your system to crash. =C2=A0That's= not > resilient behaviour. =C2=A0Yes, the data on the ZFS raidz1 should survive= the > crash and the reboot, but the point is ZFS raidz1 should be able to > survive a disk failure like that /without/ a system crash. > Ah! I understand. Thank you for the explanation.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAKOHg=PxYFJC2uOD04%2BaxHUziaxXofU-qfyvS_Xm-NqNnWtCSw>