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Conway S. Smith, mused, then expounded: |
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> |
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> About registered vs. unbuffered memory, my understanding is that for |
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> systems w/ lots of memory (more than 4 GiB), the registers are a Good |
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> Thing(tm). I don't really understand the electrical engineering behind |
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> how memory & memory controllers work, so I don't claim to really grok |
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> why registered memory is so important in systems w/ lots of RAM, but |
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> since I'm planning on loading it with 8 or 16 GiB, I was planning on |
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> going with registered anyway. |
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> |
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|
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Registered memory is needed when the system is running 24x7 and when |
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a large number of DIMMS are used due to trace lengths to the DIMMS. |
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|
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Adding registers causes power comsuption to go up as each DIMM now |
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has around 5 W of standing power, even when the memory is not in use. |
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It also results in a performance hit as the registers cause more latency. |
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|
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Whether registered memory (fo FB-DIMMs for the Intel side) are required, |
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is really up to you and your choices. However, without a really good |
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memory diag that runs on the os, along with logging the sel/event errors |
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and knowing that the running bios is actually logging memory errors |
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properly, registered memory is close to worthless for the majority |
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of home builders. Because without the proper tools, you don't know |
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that your memory is functioning properly. And the more DIMMs you |
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use the more errors you'll see (assuming the bios is reporting them) |
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and the more DIMMs you'll go through during the burn-in period, until |
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you finally get a stable system. |
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|
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> |
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> Interesting, most of what I've heard about Tyan has been really good. |
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> Is there something specific about Tyan that's been a problem for you? |
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> I've also heard good things about Gigabyte, but Tyan really seemed to |
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> stand out as excellent. The two dual-socket F Gigabyte boards on |
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> NewEgg are cheaper than the Tyans I've been considering, but |
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> unfortunately they don't support the new Barcelona Opterons, and I'd |
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> have to wait for new versions to be released. But then the Tyan |
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> motherboard I liked best is in the same situation, w/ a new |
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> Barcelona-compatible version expected later this month. I'll keep the |
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> Gigabytes in mind. |
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> |
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|
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Server motherboards tend to be better tested and have less bleeding edge |
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hardware - I had to compile the Agere GigE driver for the ECS motherboard |
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I had, before I grew tired of the other flakeyness and swapped in a Tyan |
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server motherboard. |
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|
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> |
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> RAM I mentioned above. Hard disk space was actually the main thing |
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> that's prompting this new box, as I'm filling up all my current disks. |
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> I eventually plan on filling the case w/ as many hard disks as it can |
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> fit, probably at least 10+. This box is going to be my home fileserver |
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> for a long time to come. But for starters I'm thinking I'll get 3x |
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> 1TiB in RAID5, and then grow the RAID as it fills up & drive prices |
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> drop. This will be my first time setting up RAID, I'm planning on |
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> following the HOWTO_Setup_fully_crypted_Gentoo_on_EVMS in the |
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> gentoo-wiki. |
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> |
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|
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After spending significant time with both software RAID5 and hardware |
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RAID1 and RADI5, and trashing both in ways all the docs say is not |
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possible, I find RAID is very oversold for it's supposed benefits. |
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I'd like to offer some suggestions (which are worth exactly what |
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you're paying to see them) - |
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|
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- Make the file server a sperate box, do not run your desktop on |
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the same box. You'll trash it one way or another at some point. |
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Also, that allows you to power down the the desktop and leave |
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the file server running, should you feel wasting electricity |
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is justified. And the fileserver can use less powerful cpus. |
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|
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- Minimize the number of drives. The more drives, the sooner the |
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box will fail. Stay away from RAID if it's possible. Use something |
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like LVM and individual drives - Google around for Linux video |
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recorder for some experiences in this area. |
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|
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- Don't buy drives from the same lot. If one fails then there is a |
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significantly high chance another will fail at the same time. If |
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you really insist on a RAID above 0 or 1, buy double the number |
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of drives and expect only half of them will actually work in |
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the target RAID after you burn them in for 2 weeks, including |
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power cycling. |
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|
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- Statistically, RAID 0/1 will provide greater reliability, due |
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to having only 2 drives, thus providing higher reliability. More |
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than 2 drives starts to lower reliability, requireing the need |
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to have an ECC drive (RAID5) or two (RAID6). For better reliability, |
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one needs to go to SAS drives, but then one has to use a better |
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controller than is found on most motherboards, thus increasing the |
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cost and parts count, lowering the overall reliabilty, requiring |
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more drives - hot spares. |
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|
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- If you intend on ever moving the drives from one system to another, |
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stay far away from hardware RAID. It will bite you big time on this |
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as the raid must be re-integrated each time the drives move. Even |
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pulling the drives out and re-installing. But it is dependant upon |
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the specific firmware used in the specific RAID card. And that |
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firmware varies even though the exact same RAID chip is implemented. |
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|
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- Get to know you're recovery software and procedures. RAIDs will fail. |
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Indeed, cause the failures (or, like me use a crappy motherboard that |
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will cause failures). I've re-built my running RAID more times |
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than I care to name, and in my case, am damn glad I was was running |
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XFS so I could recover from the failures. But for most people XFS |
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is a poor choice - see the previously mentioned LVM + XFS Linux |
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video recorder. |
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|
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Given that there are now 1 TB drives, the need for a RAID at home is becoming |
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less and less. |
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|
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Bob |
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-- |
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- |
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-- |
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