Re: zfs: 9 vs current, and ZIL/L2ARC on ssd?
hello Greg. Zfs seems to be much more stable in -current than 9.x. In particular, if you're using xen, then you definitely want -current because ZFS and xen under 9.x use different maxphys values for data transfers, which leads to a lot of corruption and crashes when using zfs as backingstore for xen domains. Also, under -current, dom0 can be a multi-vcpu system, which should help performance significantly when it comes to i/o on the domu's, especially if running any kind of hvm or pvh domain. Hope that helps. -thanks -Brian On Feb 11, 1:17pm, Greg Troxel wrote: } Subject: zfs: 9 vs current, and ZIL/L2ARC on ssd? } --=-=-= } Content-Type: text/plain } } } I am about to try to use zfs for the first time and have a few } questions. } } I have a machine that is running NetBSD-9/amd64 with 2 cores, 8G of RAM, } a single 1T SSD, with a smallish root/swap/usr, and about 870 GiB free } intended for zfs. I am heading for one po0l that is not raid at all. } } I'm not all that worried about transitions or stability; this is a build } machine for packages, not particularly precious, and it being down for a } week while I fix it is no big deal. } } I will likely pivot the machine to be xen dom0; I hope that doesn't } matter much (other than 1 core only in the dom0). Or I might use nvmm, } or both. } } I might add a spinning disk later, either internal or USB. (I realize } that there, I probably want both ZIL and L2ARC on SSD. I would rather } move bits later than do things now to ease that, since I do not have an } actual plan.) } } My questions are: } } Is 9/current close enough to the same zfs code that it doesn't matter } which I run? If I'm inclined to run current for other reasons, is } that a bad idea zfs-wise? } } I understand that zfs has an intent log always, and that can be within } the pool, or one can add a ZIL device. With the pool having one } device which is an SSD, I see no point in partitioning off part of } that SSD to be the ZIL. } } I understand that zfs has ARC in RAM, and can have L2ARC on disk. } Given that the pool is on SSD, it seems pointless to split off some } for L2ARC. } } My expected answers are: } } The code is basically the same and it doesn't really matter but } probably current has some bugfixes 9 doesn't. There's no reason } current is scary becuase of zfs. } } There is no point in a ZIL on the same SSD as the pool. } } There is really no point in L2ARC on the same SSD as the pool. } } } Corrections/clues appreciated. }
Re: zfs: 9 vs current, and ZIL/L2ARC on ssd?
On Thu, 11 Feb 2021 at 18:17, Greg Troxel wrote: > > > I am about to try to use zfs for the first time and have a few > questions. > > I have a machine that is running NetBSD-9/amd64 with 2 cores, 8G of RAM, > a single 1T SSD, with a smallish root/swap/usr, and about 870 GiB free > intended for zfs. I am heading for one po0l that is not raid at all. > > I'm not all that worried about transitions or stability; this is a build > machine for packages, not particularly precious, and it being down for a > week while I fix it is no big deal. > > I will likely pivot the machine to be xen dom0; I hope that doesn't > matter much (other than 1 core only in the dom0). Or I might use nvmm, > or both. > > I might add a spinning disk later, either internal or USB. (I realize > that there, I probably want both ZIL and L2ARC on SSD. I would rather > move bits later than do things now to ease that, since I do not have an > actual plan.) > > My questions are: > > Is 9/current close enough to the same zfs code that it doesn't matter > which I run? If I'm inclined to run current for other reasons, is > that a bad idea zfs-wise? > > I understand that zfs has an intent log always, and that can be within > the pool, or one can add a ZIL device. With the pool having one > device which is an SSD, I see no point in partitioning off part of > that SSD to be the ZIL. > > I understand that zfs has ARC in RAM, and can have L2ARC on disk. > Given that the pool is on SSD, it seems pointless to split off some > for L2ARC. > > My expected answers are: > > The code is basically the same and it doesn't really matter but > probably current has some bugfixes 9 doesn't. There's no reason > current is scary becuase of zfs. I have been using zfs on -current for quite some time; the system gets upgraded 2-3 times a week, no problems so far. > > There is no point in a ZIL on the same SSD as the pool. Yes. > > There is really no point in L2ARC on the same SSD as the pool. Yes. Even if you were to have more physical disks with a different setup, l2arc and zil may not be useful; r/zfs is full with discussions on the topic. 8GB physical memory is enough to run it, but you won't have much left, my system has 20GB, I see at the moment: Memory: 9235M Act, 4606M Inact, 19M Wired, 90M Exec, 13G File, 108M Free But zfs on -current at least is quite usable; I only wonder when OpenZFS 2.0 will be ported... > > > Corrections/clues appreciated. --