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what raid can do upgrades?
Where do I get a raid system that can handle upgrades?
If I have 2 100gb disks giving 100gb mirrored space, these are the most likely upgrade scenarios: Add a 200gb disk, yielding 200gb of mirrored space (each half of the 200gb disk mirrored by one of the 100gb disks). If a 100gb disk later fails, buy a 300gb disk and get 300gb mirrored space (300gb on one side, 100gb+200gb on the other side). Add a 300gb disk, yielding 200gb of mirrored space + 100gb unmirrored. Replace a failed 100gb disk with a 300gb disk, yielding 100gb mirrored + 200gb unmirrored. Replace a failed 100gb disk with 200gb and 300gb disks, yielding 300gb mirrored space (1/3 of the 300gb disk mirrored by the remaining 100gb disk). Recognize that I only have 30gb of actively changing important data that really needs to be mirrored and the rest can be used for static, temporary, and slowly changing data, so when my 100gb starts filling up I can increase available disk space from 100gb mirrored to 30gb mirrored + 2x70gb unmirrored = 170gb total without buying any new hardware - if the raid system can only do its thing on the 30gb partitions and leave the rest for the operating system to handle normally. If I have 2 100gb disks mirrored, the chances I'm going to want to replace a failed 100gb disk with another 100gb disk are virtually nil unless one fails very prematurely, and the chances I'm going to want to buy 2 more disks to get any more space are also virtually nil. I haven't heard of a case that can hold an unlimited number of disks; having to buy pairs reduces its lifetime by as much as a factor of 2. Not only that, but by the time a disk fails, which should be =5 years if they're much good, 100gb disks may not be available any more, so I would be stuck in a dead end with a system that can't handle more than one size. The prevalent fixation on performance above all other criteria is misguided for ordinary users. I for one will not be able to detect a difference of a millisecond here and a millisecond there, but I definitely notice being put into a proprietary straightjacket that is incapable of handling any of the very most likely upgrade scenarios. I understand linux can do these but what if I need to be able to run windows too? Is raid software available to allow win9x and win2k and linux to boot and use the same raid configuration using standard disks without a raid controller? Does anyone out there have real-world experience using VMware or Connectix Virtual PC or WINE or Lindows to run windows software on linux? What about an industry standard for raid disk formats, so different operating systems and software and hardware systems are interchangeable, if a raid card fails and the vendor has gone out of the business I can buy a different controller and keep running, or I can start with raid software and later buy a hardware controller, plug it in, and be running in a few minutes? -- delete NOSPAM to reply by email |
#2
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On Wed, 25 Feb 2004 14:28:33 -0800, Walter Epp
wrote: Where do I get a raid system that can handle upgrades? If I have 2 100gb disks giving 100gb mirrored space, these are the most likely upgrade scenarios: Add a 200gb disk, yielding 200gb of mirrored space (each half of the 200gb disk mirrored by one of the 100gb disks). If a 100gb disk later fails, buy a 300gb disk and get 300gb mirrored space (300gb on one side, 100gb+200gb on the other side). Add a 300gb disk, yielding 200gb of mirrored space + 100gb unmirrored. Replace a failed 100gb disk with a 300gb disk, yielding 100gb mirrored + 200gb unmirrored. Replace a failed 100gb disk with 200gb and 300gb disks, yielding 300gb mirrored space (1/3 of the 300gb disk mirrored by the remaining 100gb disk). Recognize that I only have 30gb of actively changing important data that really needs to be mirrored and the rest can be used for static, temporary, and slowly changing data, so when my 100gb starts filling up I can increase available disk space from 100gb mirrored to 30gb mirrored + 2x70gb unmirrored = 170gb total without buying any new hardware - if the raid system can only do its thing on the 30gb partitions and leave the rest for the operating system to handle normally. If I have 2 100gb disks mirrored, the chances I'm going to want to replace a failed 100gb disk with another 100gb disk are virtually nil unless one fails very prematurely, and the chances I'm going to want to buy 2 more disks to get any more space are also virtually nil. I haven't heard of a case that can hold an unlimited number of disks; having to buy pairs reduces its lifetime by as much as a factor of 2. Not only that, but by the time a disk fails, which should be =5 years if they're much good, 100gb disks may not be available any more, so I would be stuck in a dead end with a system that can't handle more than one size. The prevalent fixation on performance above all other criteria is misguided for ordinary users. I for one will not be able to detect a difference of a millisecond here and a millisecond there, but I definitely notice being put into a proprietary straightjacket that is incapable of handling any of the very most likely upgrade scenarios. I think you're kind of overthinking this. No hardware is all things to all people and ideal for all upgrade paths. You kind of just need to get what you need now and replace it when the upgrades become too diffacult or costly. Generally with RAID your best bet is to use identical drives, and if you can, with identical firmwares. That being said I recommend picking up a Mylex U160 card on ebay with 64Megs or ram or more and start with 3x 36 gig drives. You can easily expand the array as needed with MORE technology and can get good performance and useful raid levels not possible with cheaper configs. If the case is crammed or PSU isn't beefy, or you expect the array to grow in the next year or two, pick up a decent external box for the drives. Some ppl will tell you otherwise but I recommend enabling spindle sync in many situations so SCA2 drives can be the easiest way of experimenting with this. I understand linux can do these but what if I need to be able to run windows too? Is raid software available to allow win9x and win2k and linux to boot and use the same raid configuration using standard disks without a raid controller? Does anyone out there have real-world experience using VMware or Connectix Virtual PC or WINE or Lindows to run windows software on linux? I tend to use virtual disks for virtual machines so I have no experience with what you are asking. Really any limitations or extra steps should be related to the guest OS and not VMware, et al. AFAIK access to the devices is not direct but instead goes through the host OS. What about an industry standard for raid disk formats, so different operating systems and software and hardware systems are interchangeable, if a raid card fails and the vendor has gone out of the business I can buy a different controller and keep running, or I can start with raid software and later buy a hardware controller, plug it in, and be running in a few minutes? In general this low-level stuff is card specific or manufacturer specific. That is why if you run a business on a RAIDed server you should have a spare controller and drives on site. Also you need a backup of the card's config so you can swap in a new card without having to reinitializing the array. Just remember there are many reasons why RAID does not take the place of backup. One of them is that if your controller or multiple drives die you can always replace it with something different and restore the data from tape, etc. |
#3
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Previously Walter Epp wrote:
Where do I get a raid system that can handle upgrades? If I have 2 100gb disks giving 100gb mirrored space, these are the most likely upgrade scenarios: [Scenarios snipped] No RAID can do this. But there is a way around, at least with Linux software RAID-1: Put the array in degraded mode by removing one disk (i.e. "raidsetfaulty disk2", "raidhotremove disk2". Then add your new, large one and create a degraded RAID-1 array on it (i.e. just one disk in the array). Copy your stuff over and verify. Then erase the old disk, and add it to the new array. If you want to add 200GB to 2*100GB, instead just add the new disk, create 200GB degraded RAID-1, copy over. Delete the old array, combine the two 100GB into one 200GB RAID-0 array and then add this RAID-0 array as second disk the the new RAID-1 array. After resync you will have a 200GB non-degraded RAID1 array. If you don't want to use full disks, Linux does software-RAID on partitions as well. (In fact I use it only on partitions...) This allows you to use only part of a new disk or disks of different sizes. The prevalent fixation on performance above all other criteria is misguided for ordinary users. Yes, indeed. Very much so. I for one will not be able to detect a difference of a millisecond here and a millisecond there, but I definitely notice being put into a proprietary straightjacket that is incapable of handling any of the very most likely upgrade scenarios. What can I say? "+1, Insightful", I think... And in addition with hardware RAID, you need to keep a spare controller around, since your _controller_ may die. I understand linux can do these but what if I need to be able to run windows too? Difficult. Not compatible. Is raid software available to allow win9x and win2k and linux to boot and use the same raid configuration using standard disks without a raid controller? Do. Different admin-info on the disks. (I.e. icompatible by choice.) Does anyone out there have real-world experience using VMware or Connectix Virtual PC or WINE or Lindows to run windows software on linux? Vmware works fine for Office and other business-type stuff. Not very usable for real-time like video-conferencing or gaming. At least last time I tried (which was a very long time ago.) Might work well if your CPU needs are significantly lower than what the host computer provides. My solution is to have dual-boot and some unraided space for Windows at the beginning of the first disk, and manual backup to the raided space under Linux. But since I have most of my daya and work on Linux and use MS only for gaming, this is no problem at all. What about an industry standard for raid disk formats, so different operating systems and software and hardware systems are interchangeable, if a raid card fails and the vendor has gone out of the business I can buy a different controller and keep running, or I can start with raid software and later buy a hardware controller, plug it in, and be running in a few minutes? That would be nice. And no lock-in to a particular vendor anymore. But there is no such thing. The data-part is not the problem. That is standard (at least for RAID-1, simply 1:1 copy). The problem is the additional block with the RAID administrative information. Linux e.g. puts this at the end, so you can use a Partition from a RAID-1 array also directly, unraided. Other vendors do things differently, and, as far as I can see, intentionally different from each other. Arno -- For email address: lastname AT tik DOT ee DOT ethz DOT ch GnuPG: ID:1E25338F FP:0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F "The more corrupt the state, the more numerous the laws" - Tacitus |
#4
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Walter Epp wrote:
Where do I get a raid system that can handle upgrades? If I have 2 100gb disks giving 100gb mirrored space, these are the most likely upgrade scenarios: Add a 200gb disk, yielding 200gb of mirrored space (each half of the 200gb disk mirrored by one of the 100gb disks). If a 100gb disk later fails, buy a 300gb disk and get 300gb mirrored space (300gb on one side, 100gb+200gb on the other side). Add a 300gb disk, yielding 200gb of mirrored space + 100gb unmirrored. Replace a failed 100gb disk with a 300gb disk, yielding 100gb mirrored + 200gb unmirrored. Replace a failed 100gb disk with 200gb and 300gb disks, yielding 300gb mirrored space (1/3 of the 300gb disk mirrored by the remaining 100gb disk). Recognize that I only have 30gb of actively changing important data that really needs to be mirrored and the rest can be used for static, temporary, and slowly changing data, so when my 100gb starts filling up I can increase available disk space from 100gb mirrored to 30gb mirrored + 2x70gb unmirrored = 170gb total without buying any new hardware - if the raid system can only do its thing on the 30gb partitions and leave the rest for the operating system to handle normally. If I have 2 100gb disks mirrored, the chances I'm going to want to replace a failed 100gb disk with another 100gb disk are virtually nil unless one fails very prematurely, and the chances I'm going to want to buy 2 more disks to get any more space are also virtually nil. I haven't heard of a case that can hold an unlimited number of disks; having to buy pairs reduces its lifetime by as much as a factor of 2. Not only that, but by the time a disk fails, which should be =5 years if they're much good, 100gb disks may not be available any more, so I would be stuck in a dead end with a system that can't handle more than one size. The prevalent fixation on performance above all other criteria is misguided for ordinary users. The fixation with RAID is on reliability, not performance, in most cases. The one major exception is the RAID 0 setups used for video capture but even they're going by the wayside as drive performance increases. I for one will not be able to detect a difference of a millisecond here and a millisecond there, but I definitely notice being put into a proprietary straightjacket that is incapable of handling any of the very most likely upgrade scenarios. Generally the way a RAID is upgraded if the original disk model is not available is to use a larger disk and only use part of the capacity. Most administrators are not that desperate for disk space that they'd try to reconfigure a working 100 gig RAID with 3 100 gig disks into a 200 gig RAID with 2 100 gig disks and a 200. If they needed 200 gig then they'd put together a 200 gig RAID and divert the 100 gig drives to another use. I understand linux can do these but what if I need to be able to run windows too? Is raid software available to allow win9x and win2k and linux to boot and use the same raid configuration using standard disks without a raid controller? Does anyone out there have real-world experience using VMware or Connectix Virtual PC or WINE or Lindows to run windows software on linux? What about an industry standard for raid disk formats, so different operating systems and software and hardware systems are interchangeable, if a raid card fails and the vendor has gone out of the business I can buy a different controller and keep running, or I can start with raid software and later buy a hardware controller, plug it in, and be running in a few minutes? Your best bet is to find software that will allow you to configure the RAID the way you want to and then set that RAID up in a server and run your multiboot system on a different machine accessing the data via LAN. Virtual PC for Intel boxen runs only on Windows--it is a Microsoft product--there used to be a version for OS/2 but it has been discontinued. WINE works for some things, not for others. Lindows just a Linux distribution--it uses WINE to run what Windows apps it can handle and doesn't install it by default. VMware works very nicely however you have to be aware that some of the hardware is necessarily emulated, and that you have Windows or whatever guest your running on it sharing the whole CPU with a different OS--there's a performance hit that is greater or lesser depending on exactly what you're doing but it's always there. -- delete NOSPAM to reply by email -- --John Reply to jclarke at ae tee tee global dot net (was jclarke at eye bee em dot net) |
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