Re: [zfs-discuss] ZFS RAID-10
SVM did RAID 0+1 i.e. mirrored entire sub-mirrors. However SVM mirroring did not incur the problem that Richard alludes to, i.e. a single disk failure on a sub-mirror did not take down the entire sub-mirror, because the reads and writes are smart and acted as though it was a RAID 1+0. Thus as long as there was one valid copy of data available, reads and writes would be satisfied. -Sanjay Dennis Clarke wrote: Dennis Clarke wrote: While ZFS may do a similar thing *I don't know* if there is a published document yet that shows conclusively that ZFS will survive multiple disk failures. ?? why not? Perhaps this is just too simple and therefore doesn't get explained well. That is not what I wrote. Once again, for the sake of clarity, I don't know if there is a published document, anywhere, that shows by way of a concise experiment, that ZFS will actually perform RAID 1+0 and survive multiple disk failures gracefully. I do not see why it would not. But there is no conclusive proof that it will. Note that SVM (nee Solstice Disksuite) did not always do RAID-1+0, for many years it would do RAID-0+1. However, the data availability for RAID-1+0 is better than for an equivalent sized RAID-0+1, so it is just as well that ZFS does stripes of mirrors. -- richard My understanding is that SVM will do stripes of mirrors if all of the disk or stripe components have the same geometry. This has been documented, well described and laid out bare for years. One may easily create two identical stripes and then mirror them. Then pull out multiple disks on both sides of the mirror and life goes on. So long as one does not remove identical mirror components on both sides at the same time. Common sense really. Anyways, the point is that SVM does do RAID 1+0 and has for years. ZFS probably does the same thing but it adds in a boatload of new features that leaves SVM lightyears behind. Dennis ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
Dennis Clarke wrote: Dennis Clarke wrote: While ZFS may do a similar thing *I don't know* if there is a published document yet that shows conclusively that ZFS will survive multiple disk failures. ?? why not? Perhaps this is just too simple and therefore doesn't get explained well. That is not what I wrote. Once again, for the sake of clarity, I don't know if there is a published document, anywhere, that shows by way of a concise experiment, that ZFS will actually perform RAID 1+0 and survive multiple disk failures gracefully. I do not see why it would not. But there is no conclusive proof that it will. Will add it to the solarisinternals ZFS wiki. For an easy proof, I created a RAID-1+0 set with ramdisks and clobbered two of the ramdisks. # zpool status rampool pool: rampool state: DEGRADED status: One or more devices could not be opened. Sufficient replicas exist for the pool to continue functioning in a degraded state. action: Attach the missing device and online it using 'zpool online'. see: http://www.sun.com/msg/ZFS-8000-D3 scrub: resilver completed with 0 errors on Mon Oct 23 10:58:55 2006 config: NAME STATE READ WRITE CKSUM rampool DEGRADED 0 0 0 mirror DEGRADED 0 0 0 /dev/ramdisk/set1-0 ONLINE 0 0 0 /dev/ramdisk/set1-1 UNAVAIL 0 0 0 cannot open mirror DEGRADED 0 0 0 /dev/ramdisk/set2-1 ONLINE 0 0 0 /dev/ramdisk/set2-0 UNAVAIL 0 0 0 cannot open errors: No known data errors # -- richard ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
[zfs-discuss] ZFS RAID-10
Is it possible to construct a RAID-10 array with ZFS? I've read through the ZFS documentation, and it appears that the only way to create a RAID-10 array would be to create two mirrored (RAID-1) emulated volumes in ZFS and combine those to create the outer RAID-0 volume. Am I approaching this in the wrong way? Should I be using SVM to create my RAID-1 volumes and then create a ZFS filesystem from those volumes? This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
On Sun, 22 Oct 2006, Stephen Le wrote: Is it possible to construct a RAID-10 array with ZFS? I've read through the ZFS documentation, and it appears that the only way to create a RAID-10 array would be to create two mirrored (RAID-1) emulated volumes in ZFS and combine those to create the outer RAID-0 volume. Am I approaching this in the wrong way? Should I be using SVM to create my RAID-1 volumes and then create a ZFS filesystem from those volumes? No - don't do that. Here is a ZFS version of a RAID 10 config with 4 disks: - from 817.2271.pdf - Creating a Mirrored Storage Pool To create a mirrored pool, use the mirror keyword, followed by any number of storage devices that will comprise the mirror. Multiple mirrors can be specied by repeating the mirror keyword on the command line. The following command creates a pool with two, two-way mirrors: # zpool create tank mirror c1d0 c2d0 mirror c3d0 c4d0 The second mirror keyword indicates that a new top-level virtual device is being specied. Data is dynamically striped across both mirrors, with data being replicated between each disk appropriately. --- end of quote from 817-2271.pdf page 38 Regards, Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED] Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005 OpenSolaris Governing Board (OGB) Member - Feb 2006 ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
On Oct 22, 2006, at 9:57 PM, Al Hopper wrote: On Sun, 22 Oct 2006, Stephen Le wrote: Is it possible to construct a RAID-10 array with ZFS? I've read through the ZFS documentation, and it appears that the only way to create a RAID-10 array would be to create two mirrored (RAID-1) emulated volumes in ZFS and combine those to create the outer RAID-0 volume. Am I approaching this in the wrong way? Should I be using SVM to create my RAID-1 volumes and then create a ZFS filesystem from those volumes? No - don't do that. Here is a ZFS version of a RAID 10 config with 4 disks: snip To further agree with/illustrate Al's point, here's an example of 'zpool status' output which reflects this type of configuration: (Note that there is one mirror set for each pair of drives. In this case, drive 1 on crontroller 3 is mirrored to drive 1 on controller 4, and so on. This will ensure continuity should one controller/buss/ cable fail.) [EMAIL PROTECTED]zpool status pool: data state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM data ONLINE 0 0 0 mirror ONLINE 0 0 0 c3t0d0 ONLINE 0 0 0 c4t9d0 ONLINE 0 0 0 mirror ONLINE 0 0 0 c3t1d0 ONLINE 0 0 0 c4t10d0 ONLINE 0 0 0 mirror ONLINE 0 0 0 c3t2d0 ONLINE 0 0 0 c4t11d0 ONLINE 0 0 0 mirror ONLINE 0 0 0 c3t3d0 ONLINE 0 0 0 c4t12d0 ONLINE 0 0 0 errors: No known data errors ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
On Sun, 22 Oct 2006, Stephen Le wrote: Is it possible to construct a RAID-10 array with ZFS? I've read through the ZFS documentation, and it appears that the only way to create a RAID-10 array would be to create two mirrored (RAID-1) emulated volumes in ZFS and combine those to create the outer RAID-0 volume. Am I approaching this in the wrong way? Should I be using SVM to create my RAID-1 volumes and then create a ZFS filesystem from those volumes? No - don't do that. Here is a ZFS version of a RAID 10 config with 4 disks: - from 817.2271.pdf - Creating a Mirrored Storage Pool To create a mirrored pool, use the mirror keyword, followed by any number of storage devices that will comprise the mirror. Multiple mirrors can be specied by repeating the mirror keyword on the command line. The following command creates a pool with two, two-way mirrors: # zpool create tank mirror c1d0 c2d0 mirror c3d0 c4d0 The second mirror keyword indicates that a new top-level virtual device is being specied. Data is dynamically striped across both mirrors, with data being replicated between each disk appropriately. We need to keep in mind that the exact same result may be achieved with simple SVM : d1 1 2 /dev/dsk/c1d0s0 /dev/dsk/c3d0s0 -i 512b d2 1 2 /dev/dsk/c2d0s0 /dev/dsk/c4d0s0 -i 512b d3 -m d1 metainit d1 metainit d2 metainit d3 metattach d3 d2 At this point, if and only if all stripe components come from exactly identical geometry disks or slices, you get a stripe of mirrors and not just a mirror of stripes. While ZFS may do a similar thing *I don't know* if there is a published document yet that shows conclusively that ZFS will survive multiple disk failures. However ZFS brings a lot of other great features. Dennis Clarke ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
Dennis Clarke wrote: While ZFS may do a similar thing *I don't know* if there is a published document yet that shows conclusively that ZFS will survive multiple disk failures. ?? why not? Perhaps this is just too simple and therefore doesn't get explained well. Note that SVM (nee Solstice Disksuite) did not always do RAID-1+0, for many years it would do RAID-0+1. However, the data availability for RAID-1+0 is better than for an equivalent sized RAID-0+1, so it is just as well that ZFS does stripes of mirrors. -- richard ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] ZFS RAID-10
Dennis Clarke wrote: While ZFS may do a similar thing *I don't know* if there is a published document yet that shows conclusively that ZFS will survive multiple disk failures. ?? why not? Perhaps this is just too simple and therefore doesn't get explained well. That is not what I wrote. Once again, for the sake of clarity, I don't know if there is a published document, anywhere, that shows by way of a concise experiment, that ZFS will actually perform RAID 1+0 and survive multiple disk failures gracefully. I do not see why it would not. But there is no conclusive proof that it will. Note that SVM (nee Solstice Disksuite) did not always do RAID-1+0, for many years it would do RAID-0+1. However, the data availability for RAID-1+0 is better than for an equivalent sized RAID-0+1, so it is just as well that ZFS does stripes of mirrors. -- richard My understanding is that SVM will do stripes of mirrors if all of the disk or stripe components have the same geometry. This has been documented, well described and laid out bare for years. One may easily create two identical stripes and then mirror them. Then pull out multiple disks on both sides of the mirror and life goes on. So long as one does not remove identical mirror components on both sides at the same time. Common sense really. Anyways, the point is that SVM does do RAID 1+0 and has for years. ZFS probably does the same thing but it adds in a boatload of new features that leaves SVM lightyears behind. Dennis ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
