Re: [zfs-discuss] Couple of questions about ZFS on laptops
On Nov 9, 2011, at 6:08 PM, Francois Dion wrote: Some laptops have pc card and expresscard slots, and you can get an adapter for sd card, so you could set up your os non mirrored and just set up home on a pair of sd cards. Something like http://www.amazon.com/Sandisk-SDAD109A11-Digital-Card-Express/dp/B000W3QLLW I've done this in the past, variations of this, including using a partition and a usb stick: SDcard is suitable for boot *only* if it is connected via USB. While the drivers I wrote for SDHCI work fine for using media, you can't boot off it generally -- usually the laptop BIOS simply lacks the support needed to see these. It used to be that CompactFlash was a preferred option, but I think CF is falling out of favor these days. - Garrett http://solarisdesktop.blogspot.com/2007/02/stick-to-zfs-or-laptop-with-mirrored.html Wow, where did the time go, that was almost 5 years ago... Anyway, i pretty much ditched carrying the laptop, the current one i have is too heavy (m4400). But it does run really nicely sol11 and openindiana. The m4400 is set up with 2 drives, not mirrored. I'm tempted to put a sandforce based ssd for faster booting and better zfs perf for demos. Then i have an sdcard and expresscard adapter for sd. This gives me 16gb mirrored for my documents, which is plenty. Francois Sent from my iPad On Nov 8, 2011, at 12:05 PM, Jim Klimov jimkli...@cos.ru wrote: Hello all, I am thinking about a new laptop. I see that there are a number of higher-performance models (incidenatlly, they are also marketed as gamer ones) which offer two SATA 2.5 bays and an SD flash card slot. Vendors usually position the two-HDD bay part as either get lots of capacity with RAID0 over two HDDs, or get some capacity and some performance by mixing one HDD with one SSD. Some vendors go as far as suggesting a highest performance with RAID0 over two SSDs. Now, if I were to use this for work with ZFS on an OpenSolaris-descendant OS, and I like my data enough to want it mirrored, but still I want an SSD performance boost (i.e. to run VMs in real-time), I seem to have a number of options: 1) Use a ZFS mirror of two SSDs - seems too pricey 2) Use a HDD with redundant data (copies=2 or mirroring over two partitions), and an SSD for L2ARC (+maybe ZIL) - possible unreliability if the only HDD breaks 3) Use a ZFS mirror of two HDDs - lowest performance 4) Use a ZFS mirror of two HDDs and an SD card for L2ARC. Perhaps add another built-in flash card with PCMCIA adapters for CF, etc. Now, there is a couple of question points for me here. One was raised in my recent questions about CF ports in a Thumper. The general reply was that even high-performance CF cards are aimed for linear RW patterns and may be slower than HDDs for random access needed as L2ARCs, so flash cards may actually lower the system performance. I wonder if the same is the case with SD cards, and/or if anyone encountered (and can advise) some CF/SD cards with good random access performance (better than HDD random IOPS). Perhaps an extra IO path can be beneficial even if random performances are on the same scale - HDDs would have less work anyway and can perform better with their other tasks? On another hand, how would current ZFS behave if someone ejects an L2ARC device (flash card) and replaces it with another unsuspecting card, i.e. one from a photo camera? Would ZFS automatically replace the L2ARC device and kill the photos, or would the cache be disabled with no fatal implication for the pools nor for the other card? Ultimately, when the ex-L2ARC card gets plugged back in, would ZFS automagically attach it as the cache device, or does this have to be done manually? Second question regards single-HDD reliability: I can do ZFS mirroring over two partitions/slices, or I can configure copies=2 for the datasets. Either way I think I can get protection from bad blocks of whatever nature, as long as the spindle spins. Can these two methods be considered equivalent, or is one preferred (and for what reason)? Also, how do other list readers place and solve their preferences with their OpenSolaris-based laptops? ;) Thanks, //Jim Klimov ___ 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 ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Couple of questions about ZFS on laptops
Some laptops have pc card and expresscard slots, and you can get an adapter for sd card, so you could set up your os non mirrored and just set up home on a pair of sd cards. Something like http://www.amazon.com/Sandisk-SDAD109A11-Digital-Card-Express/dp/B000W3QLLW I've done this in the past, variations of this, including using a partition and a usb stick: http://solarisdesktop.blogspot.com/2007/02/stick-to-zfs-or-laptop-with-mirrored.html Wow, where did the time go, that was almost 5 years ago... Anyway, i pretty much ditched carrying the laptop, the current one i have is too heavy (m4400). But it does run really nicely sol11 and openindiana. The m4400 is set up with 2 drives, not mirrored. I'm tempted to put a sandforce based ssd for faster booting and better zfs perf for demos. Then i have an sdcard and expresscard adapter for sd. This gives me 16gb mirrored for my documents, which is plenty. Francois Sent from my iPad On Nov 8, 2011, at 12:05 PM, Jim Klimov jimkli...@cos.ru wrote: Hello all, I am thinking about a new laptop. I see that there are a number of higher-performance models (incidenatlly, they are also marketed as gamer ones) which offer two SATA 2.5 bays and an SD flash card slot. Vendors usually position the two-HDD bay part as either get lots of capacity with RAID0 over two HDDs, or get some capacity and some performance by mixing one HDD with one SSD. Some vendors go as far as suggesting a highest performance with RAID0 over two SSDs. Now, if I were to use this for work with ZFS on an OpenSolaris-descendant OS, and I like my data enough to want it mirrored, but still I want an SSD performance boost (i.e. to run VMs in real-time), I seem to have a number of options: 1) Use a ZFS mirror of two SSDs - seems too pricey 2) Use a HDD with redundant data (copies=2 or mirroring over two partitions), and an SSD for L2ARC (+maybe ZIL) - possible unreliability if the only HDD breaks 3) Use a ZFS mirror of two HDDs - lowest performance 4) Use a ZFS mirror of two HDDs and an SD card for L2ARC. Perhaps add another built-in flash card with PCMCIA adapters for CF, etc. Now, there is a couple of question points for me here. One was raised in my recent questions about CF ports in a Thumper. The general reply was that even high-performance CF cards are aimed for linear RW patterns and may be slower than HDDs for random access needed as L2ARCs, so flash cards may actually lower the system performance. I wonder if the same is the case with SD cards, and/or if anyone encountered (and can advise) some CF/SD cards with good random access performance (better than HDD random IOPS). Perhaps an extra IO path can be beneficial even if random performances are on the same scale - HDDs would have less work anyway and can perform better with their other tasks? On another hand, how would current ZFS behave if someone ejects an L2ARC device (flash card) and replaces it with another unsuspecting card, i.e. one from a photo camera? Would ZFS automatically replace the L2ARC device and kill the photos, or would the cache be disabled with no fatal implication for the pools nor for the other card? Ultimately, when the ex-L2ARC card gets plugged back in, would ZFS automagically attach it as the cache device, or does this have to be done manually? Second question regards single-HDD reliability: I can do ZFS mirroring over two partitions/slices, or I can configure copies=2 for the datasets. Either way I think I can get protection from bad blocks of whatever nature, as long as the spindle spins. Can these two methods be considered equivalent, or is one preferred (and for what reason)? Also, how do other list readers place and solve their preferences with their OpenSolaris-based laptops? ;) Thanks, //Jim Klimov ___ 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] Couple of questions about ZFS on laptops
On Tue, 8 Nov 2011, Jim Klimov wrote: Second question regards single-HDD reliability: I can do ZFS mirroring over two partitions/slices, or I can configure copies=2 for the datasets. Either way I think I can get protection from bad blocks of whatever nature, as long as the spindle spins. Can these two methods be considered equivalent, or is one preferred (and for what reason)? Using two partitions on the same disk seems to give you most of the headaches associated with more disks without much of the benefit. If there is any minor issue, you will see zfs resilvering partitions and resilvering will be slow due to the drive heads flailing back and forth between partitions. There is also the issue that the block allocation is not likely to be very efficient in terms of head movement if two partitions are used. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Couple of questions about ZFS on laptops
2011-11-08 23:36, Bob Friesenhahn wrote: On Tue, 8 Nov 2011, Jim Klimov wrote: Second question regards single-HDD reliability: I can do ZFS mirroring over two partitions/slices, or I can configure copies=2 for the datasets. Either way I think I can get protection from bad blocks of whatever nature, as long as the spindle spins. Can these two methods be considered equivalent, or is one preferred (and for what reason)? Using two partitions on the same disk seems to give you most of the headaches associated with more disks without much of the benefit. If there is any minor issue, you will see zfs resilvering partitions and resilvering will be slow due to the drive heads flailing back and forth between partitions. There is also the issue that the block allocation is not likely to be very efficient in terms of head movement if two partitions are used. Thanks, Bob, I figured so... And would copies=2 save me from problems of data loss and/or inefficient resilvering? Does all required data and metadata get duplicated this way, so any broken sector can be amended? I read on this list recently, that some metadata is already copies=2 or =3. To what extent?.. Should the trunk of the ZFS block tree be expected always secured, even on one disk? Thanks, //Jim Klimov ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Couple of questions about ZFS on laptops
On Wed, 9 Nov 2011, Jim Klimov wrote: Thanks, Bob, I figured so... And would copies=2 save me from problems of data loss and/or inefficient resilvering? Does all required data and metadata get duplicated this way, so any broken sector can be amended? I read on this list recently, that some metadata is already copies=2 or =3. To what extent?.. Should the trunk of the ZFS block tree be expected always secured, even on one disk? With only one disk partition in a vdev, then there will be no resilvering since there is nothing to resilver. Metadata has always stored at least two copies. It is always possible to lose the whole pool if the device does not work according to specification (or you drop the laptop on the ground). Using copies=2 and doing a 'zfs scrub' at least once after bulk data has been written should help avoid media read errors. Zfs will still resilver blocks which failed to read as long as there is a redundant copy. If you do want to increase reliability then you should mirror between disks, even if you feel that this will be slow. It will still be faster (for reads) than using just one disk. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Couple of questions about ZFS on laptops
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- boun...@opensolaris.org] On Behalf Of Jim Klimov 1) Use a ZFS mirror of two SSDs - seems too pricey 2) Use a HDD with redundant data (copies=2 or mirroring over two partitions), and an SSD for L2ARC (+maybe ZIL) - possible unreliability if the only HDD breaks 3) Use a ZFS mirror of two HDDs - lowest performance 4) Use a ZFS mirror of two HDDs and an SD card for L2ARC. Perhaps add another built-in flash card with PCMCIA adapters for CF, etc. The performance of a SSD or flash drive or SD card is almost entirely dependent on the robustness/versatility of the built-in controller circuit. You can rest assured that no SD card and no USB device is going to have performance even remotely close to a decent SSD, except under the conditions that are specifically optimized for that device. The manufacturers, of course, will publish their maximum specs, and the real world usage of the device might be an order of magnitude lower. A little while back, I performed an experiment - I went out and bought the best rated, most expensive USB3 flash drives I could find, and I benchmarked them against the cheapest USB2 hard drives I could find. The hard drives won by a clear margin, like 4x to 8x faster, except when running large sequential dd to/from the raw flash device on the first boot - in which case the flash won by a small margin (like 10%) Given your hardware limitations, the only way to go fast is to use a SSD, and the only way to go fast with redundancy is to use a mirror of two SSD's. If you don't go for the SSD's, then your HDD's will be the second fastest option. Do not put any SD card into the mix. It will only hurt you. Second question regards single-HDD reliability: I can do ZFS mirroring over two partitions/slices, or I can configure copies=2 for the datasets. Either way I think I can get protection from bad blocks of whatever nature, as long as the spindle spins. Can these two methods be considered equivalent, or is one preferred (and for what reason)? I would opt for the copies=2 method, because it's reconfigurable if you want, and it's designed to work within a single pool, so it more closely resembles your actual usage. If you mirror across two partitions on the same disk, there may be unintended performance consequences because nobody expected you to do that when they wrote the code. Also, how do other list readers place and solve their preferences with their OpenSolaris-based laptops? ;) I'm sorry to say, there is no ZFS-based OS and no laptop hardware that I consider to be a reliable combination. Of course I haven't tested them all, but I don't believe in any of them because it's unintended, uncharted, untested, unsupported. I think you'll find the best support for this subject on the openindiana mailing lists. After oracle acquired sun, most of the home users and laptop users left the opensolaris mailing lists in favor of the openindiana lists. The people that remain here are primarily focused on enterprise and servers. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
