Thanks, I'll be printing that out to re-read it again later in the week. Using AD currently, trying to move to Kerb+LDAP+TheRest, but it's going to be a few years until we get rid of the Win servers (even for a small 8-server shop).
I mostly have an idea of what Radius is. But not entirely. I didn't even know there was something called FreeRadius. So what solution is Radius for and where does it fit into the universe of LDAP / Kerberos / Active Directory / etc?
Satellites are junk (always have been), they're the consumer level line.
For desktop replacement, my preference is still either a Toshiba Tecra M3 (not a tablet) or the Thinkpad T60/T60p line. Get the 1400x1050 display and a dual-core CPU, 2GB of RAM and you've got a 6-8 year machine. The 17" display doesn't cut it in my book, I'd rather attach a secondary display positioned beside or above my 14"/15" laptop screen.
Possibly the 13" MacBook or the slightly larger 15" MacBooks...
(Hell, I'm typing this on a 4.5 year old Tecra 9100. Which is a slow and hot Pentium 4 M 1.8GHz w/ 1GB of RAM and a 1400x1050 display. Replaced the keyboard, mouse buttons, hard drive... twice... and the DVD/CD over the past few years. Next year I'll replace the backlight and finally hand it off to a less demanding user. I'm sure it needs a new battery as well, but I'm always connected in various locations. I've used the machine about 12 hours per day, 6 days per week. I keep saying that I'm going to upgrade, but now I'm probably going to wait for the Core2's and being able to get 4GB of RAM installed from the outset.)
Trackpoints excel at the job of doing 95% typing and about 5% mouse control. I mostly use the trackpoint to click on dialogs because (unlike OS/2 of yore), Windows doesn't do a very good job of letting you do everything with the keyboard. So every few minutes, I'd have to take my hands off the home row and change focus with the mouse.
It also helps if you set the mouse speed to maximum when using a trackpoint. That allows for a gentler touch on the trackpoint (at least on the Toshiba Tecra) and gets you across the screen quicker. It's definitely an acquired skill to deal with a trackpoint that is set to maximum sensitivity. After 6 years of using the pointer on the Toshiba Tecras, I'm very comfortable with it.
I must be the only one here who prefers the "nipple" to a trackpad. I tend to have more control with it than the trackpad, and it's quicker to get to than a trackpad, as it's in the middle of the keyboard. I barely have to shift my hand to be able to control it.
Nope, there's lots of us out there who prefer the trackpoint (available on Toshiba Tecra as well, which is what I've used for 6 years now). In fact, I just replaced the keyboard and mouse buttons on my Tecra this past spring, which makes it feel like a brand-new system instead of 4.5 years old.
For a touch-typist, the trackpoint is a great tool for moving the mouse cursor to click on dialogs or reposition the cursor without taking my hands off the home row. It also comes in handy in tight quarters (airline / train seats, small desks, sitting in the easy chair) where an external mouse is a problem.
I do mostly programming and systems administration. The trackpoint meets my needs very well. If I was doing GUI design or graphics, I'd definitely dig out the external mouse and use that.
Come to think of it... I'm not even sure where my external mouse is. Probably got shoved off the back of the desk and is down in 'cord hell'. I'll probably fish it out sometime next year.
Re:Some insights about the article
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Crypto Snake Oil
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· Score: 1
Cryptography is hard.
I prefer to say that cryptography is easy, it's the implementation of the cryptography that is fiendishly difficult. And key-management is even more difficult. (There are enough published cryptography algorithms and PRNG algorithms that are widely trusted and generally considered secure. Things generally fall apart in other areas, usually key management.)
Re:No, it's much harder than you think.
on
Crypto Snake Oil
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· Score: 1
IIRC, he talks about it again in Practical Cryptography (regarding the naivety of Applied Cryptography). I think... I've been reading both books at around the same time, so things get mixed up.
Re:How is this different from any other product?
on
Crypto Snake Oil
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· Score: 1
Schneier comes up a lot because he's done a very good job of bridging the gap between mere mortals and those who work on crypto systems. Books like Secrets and Lies or his CRYPTO-GRAM monthly e-mail newsletter where he explains crypto systems in plain english.
I get a kick out of reading about products in the "doghouse" in the monthly CRYPTO-GRAM.
(I know just enough about cryptography to know that I shouldn't try to roll my own...)
Without digging out my copy of Practical Cryptography, CBC also suffers the same flaw or similar flaw as ECB. It's the reason that the TrueCrypt folks switched from CBC to LRW for disk encryption. (And why tweaked CBC algorithms are popular.)
Rather then add what other posters have said... I'll leave it at this.
Go check out a copy (or purchase) of Practical Cryptography by Ferguson and Schneier. Read the first few chapters which discuss things like known-plaintext attacks, why we use block ciphers and what the estimated strength of the various algorithms are. The rest of the book gets into the nitty-gritty details, but the start of the book is suitable for anyone with more then a passing interest in crypto.
After that (or before that) you should also read Secrets and Lies which will help you to put things into perspective. Schneier does a very good job of arming the reader with the knowledge needed to make informed decisions about the process of security. Encryption is generally worthless without considering the overall picture.
As Schneier (and others) have said. Encryption is like a very sturdy pole in the ground. It's merely one part of the security system and often not even the weakest point of attack.
A rough guideline is that a 600MHz VIA C3 (fanless) is about half the processing power of a Celeron 566MHz (Pentium III core). That's based on personal experience and not anything scientific.
OTOH, that little VIA C3 system on my shelf draws a miniscule amount of power (including the 2 laptop HDDs). Makes a very good firewall PC for my home network.
(Yes, I know about the Linksys router that runs Linux. No, I don't own one. I had the VIA C3 sitting around from a previous project.)
Get one of those case thermometers and tape the lead to the side of the drive. Maybe the SMART chip reads high on the drive, or it's not talking correctly to your motherboard.
Alternately, there's the "touch" test. If the drive feels too hot to be comfortably touched, it's too hot to live long. A well cooled drive will feel cool to the touch, even under heavy loads.
So, what HD would you use in your desktop box, if you had to replace a drive today?
I'd worry more about making sure the drive stays below 45C (or even below 40C if you can swing it). Above 45C and the drive is probably too warm to survive for long. Above 50C and it's almost certain to die an early death.
A good power-supply and good AC power (i.e. use a good server-quality UPS if your AC power is flaky) is also a good idea. I've seen perfectly good drives drop out of RAID arrays due to flaky power, causing extra rebuilds or even loss of the array if too many drop out at the same time.
Beyond that, I'd go with either 3-year or 5-year warranty products. Leaning towards the 5-year warranty drives because they (hopefully) will be of slightly better quality. All of the manufacturers with the 5-year warranty drives are about equal on quality (or lack thereof).
Remember, plan for drive failure. That drive will die and always at the worst possible time.
Most people rely so heavily on Seagate, but five year warranty is commonplace nowadays and the fact is that these drives fail as often as other major brands (more or less).
It's somewhat difficult to find a hard drive with a 5-year warranty that isn't a Seagate. For instance, looking at the 19 hard drives that are 400GB or larger at NewEgg:
(2) are 1-year warranty
(6) are 3-year warranty
(11) are 5-year warranty (2 are WD, rest are Seagate)
In that very small sample, the majority of Seagates (all?) come with 5-year warranties, while only a small portion of Western Digital's line comes with a 5-year warranty. The rest of WD's drives are either 1-year or 3-year warranty.
So for the average consumer, it's easier to say "get a Seagate" for the long warranty then it is to tell them to look at the fine print on the back of the box to figure out the warranty period.
The only brand I've had worse luck with is IBM DeskStar. Though thanks to an 100% failure rate, I no longer have any of them.
(shrugs) I bought about two dozen DeskStars over the last 8 years. Sizes were anything from 13GB up to 80GB. Probably 80-90% of them are still humming away in machines.
Most of the ones that did fail could be linked (mostly) to either poor power or poor cooling. Which, come to think of it, describes the vast majority of hard drive failures that I've seen over the past decade. Keep them cool, give them good power and they'll last near forever barring any manufacturing defects.
(There's the possible correllation that drives with manufacturing defects are more affected by poor cooling / power, thus failing sooner...)
It depends on the person's preferred method of communication. (I'm sure I'll mess up the categorizations.) Most people prefer one specific type with less preference for the others. Some folks are equally comfortable with multiple types.
Tactile? Those are the face-to-face meeting folks. They're not comfortable unless they can see you in the same room and watch the body language. They process new things by working with them in a hands-on fashion.
Visual? The e-mail and IM gods. Written is best for them. Very good readers (they tend to learn a lot from written texts).
Aural? The phone for everything folks. Or a cross-over with the face-to-face meeting folks. They are great at communicating and learning via verbal communication. These folks can repeat a conversation verbatim (or darn close).
I forget what the estimates are for the population at large for each category. But a lot of aural-centric folks simply aren't wired for communicating via e-mail / IM and have to be taught. They might come across as abrupt in written communications or leave IM conversations without saying goodbye.
I work for a company in the UK which works with a company in the States. Sometime I have to email fairly technical (ie its about source code and programming in general) messages to my counterpart in the States. To make the process as simple as possible I spend some time breaking my question(s) into pieces, numbering them, and making them clear and hopefully straight-forward. The American company practically *always* only replies to the first point in the email. If their reply addresses the problem, we still have all the others to go through, as could be seen if they'd been read at the time the first one was.
(I'm being somewhat funny, but I think it's the main reason why. If you're top-posting, then you have to scroll up/down to see the entire message that you're replying to. That or the frequent use of preview windows where you only see the upper portion of the message.)
I have a W2K system at home with only a 1/2 gig of ram and I have never, EVER, had any memory issues. And yes, I do leave my browser open for days on end.
Exactly... the reason why you never see problems is because you only have 512MB of RAM.
The primary issue with Firefox is that once you have 1GB or more, Firefox gets over-aggressive with memory use. Mostly the setting that has to do with how many previous pages are saved for each tab (window?). Below 1GB and it's set at a reasonable number, but with 1GB, suddenly the automatically configured value doubles (more?) so that Firefox goes from taking up 100MB of RAM to using 300MB of RAM.
The setting is "browser. sessionhistory. max_total_viewers" (spaces inserted to fool the Slashdot filter). The default value is -1 which allows Firefox to configure this value automatically. I've forced mine to "2" instead of the automatically configured "8".
Which keeps Firefox to a somewhat svelte 100-120MB in use (200MB peak) instead of the 300-400MB monstrosity that it was before.
Make it so that every window runs in a separate thread so that a crash in one window doesn't affect the other windows. I'd be happier if every tab was its own thread, but a separate process for each window would work well enough.
Re:Wasn't firefox designed as the simple mozilla?
on
Marketing Mozilla
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· Score: 1
The mozilla suite was replaced by discrete components because thats what people wanted - AND ITS WORKED.
Here's why I switched from the Mozilla Suite to Firefox + Thunderbird:
Stability
I got tired of crashes in one part of Mozilla (usually the web browser) wiping out my e-mail client at the same time. Hell, it's bad enough that Firefox, when it crashes, wipes out all of its windows instead of simply closing the affected tab (or window).
Maybe it's time to move to Opera instead... I don't even run more then 3 extensions and Firefox still dies about once a week, usually in the middle of my workday when I have 6 windows and 30 tabs open. After a while I wonder why I'm continuing to use Firefox.
About the only thing I'd use them for is a PostgreSQL xlog location (the scratch area that PostgreSQL writes to prior to committing the writes to the database). It's all sequential writes, not very high volume, but when the xlog is on the same spindle as the database you get a lot of contention and slowdown in write-heavy applications.
Even then, I'd probably replace the 5GB drive with a more modern 300GB or 400GB spindle. Create 5GB for the swap area on it, use the rest for temp directories, the xlog, and a quick-n-dirty backup location for rsync snapshots.
(Older drives are *really* slow... 5-10MB/s vs 30+ MB/s for a more modern drive. The 750GB drives do 75MB/s at the outer diameter.)
1) Performance - Average I/O time for a 4-drive RAID10 array is 1/2 that of a 2-drive RAID1 array on average. Throughput also steps somewhat linearly as you add more drives to a RAID10 array. RAID5 is fine for read-oriented storage, but not so good at writes. RAID10 allows us to improve throughput of both reads and writes.
2) Rebuild time - Rebuild time for a RAID5 array isn't all that great. And if a 2nd drive fails, you have a 100% chance of data loss (vs only a 50% chance with RAID10). There's the possibility that RAID6 would be a better fit.
For a 4-6 drive RAID, I've never been happy with RAID5 performance. Maybe it makes more sense at the 8-12 drive mark. Although at that level of spindles, you'd better be running RAID6 with hot-spares.
If this was a backup storage server, we might go the RAID6 route... in which case capacity trumps performance. (Anyone know what performance gain is on a 8 or 12 drive RAID6 array?)
Might be able to do it with an Antec Overture II case. Heat might be an issue though. Plus it takes a standard microATX motherboard.
Could put a 3:2 hot-swap SATA enclosure or a 3:2 bay cooler (80mm fan) in the front 2 5.25" bays. With one or two more drives in the rear internal 3.5" drive bay.
Still might be too large.
(We're considering using the Overture II cases as Xen head units. We don't have a real server rack, but the Overture II units are slim enough that we can pack them in tightly on a 30"x24" chrome shelf unit. Plus, since we're using Xen, we can move services between units on the fly.)
Slashdot Mirror
Thanks, I'll be printing that out to re-read it again later in the week. Using AD currently, trying to move to Kerb+LDAP+TheRest, but it's going to be a few years until we get rid of the Win servers (even for a small 8-server shop).
(Another reason why I read Slashdot...)
I mostly have an idea of what Radius is. But not entirely. I didn't even know there was something called FreeRadius. So what solution is Radius for and where does it fit into the universe of LDAP / Kerberos / Active Directory / etc?
Thanks!
Satellites are junk (always have been), they're the consumer level line.
For desktop replacement, my preference is still either a Toshiba Tecra M3 (not a tablet) or the Thinkpad T60/T60p line. Get the 1400x1050 display and a dual-core CPU, 2GB of RAM and you've got a 6-8 year machine. The 17" display doesn't cut it in my book, I'd rather attach a secondary display positioned beside or above my 14"/15" laptop screen.
Possibly the 13" MacBook or the slightly larger 15" MacBooks...
(Hell, I'm typing this on a 4.5 year old Tecra 9100. Which is a slow and hot Pentium 4 M 1.8GHz w/ 1GB of RAM and a 1400x1050 display. Replaced the keyboard, mouse buttons, hard drive... twice... and the DVD/CD over the past few years. Next year I'll replace the backlight and finally hand it off to a less demanding user. I'm sure it needs a new battery as well, but I'm always connected in various locations. I've used the machine about 12 hours per day, 6 days per week. I keep saying that I'm going to upgrade, but now I'm probably going to wait for the Core2's and being able to get 4GB of RAM installed from the outset.)
Trackpoints excel at the job of doing 95% typing and about 5% mouse control. I mostly use the trackpoint to click on dialogs because (unlike OS/2 of yore), Windows doesn't do a very good job of letting you do everything with the keyboard. So every few minutes, I'd have to take my hands off the home row and change focus with the mouse.
It also helps if you set the mouse speed to maximum when using a trackpoint. That allows for a gentler touch on the trackpoint (at least on the Toshiba Tecra) and gets you across the screen quicker. It's definitely an acquired skill to deal with a trackpoint that is set to maximum sensitivity. After 6 years of using the pointer on the Toshiba Tecras, I'm very comfortable with it.
Toshiba Tecras are the only other business class system that I know of with a trackpoint-style pointing device.
(It's also a deciding factor on my part. I can't live without it which means either Toshiba Tecra or Lenovo Thinkpad.)
I must be the only one here who prefers the "nipple" to a trackpad. I tend to have more control with it than the trackpad, and it's quicker to get to than a trackpad, as it's in the middle of the keyboard. I barely have to shift my hand to be able to control it.
Nope, there's lots of us out there who prefer the trackpoint (available on Toshiba Tecra as well, which is what I've used for 6 years now). In fact, I just replaced the keyboard and mouse buttons on my Tecra this past spring, which makes it feel like a brand-new system instead of 4.5 years old.
For a touch-typist, the trackpoint is a great tool for moving the mouse cursor to click on dialogs or reposition the cursor without taking my hands off the home row. It also comes in handy in tight quarters (airline / train seats, small desks, sitting in the easy chair) where an external mouse is a problem.
I do mostly programming and systems administration. The trackpoint meets my needs very well. If I was doing GUI design or graphics, I'd definitely dig out the external mouse and use that.
Come to think of it... I'm not even sure where my external mouse is. Probably got shoved off the back of the desk and is down in 'cord hell'. I'll probably fish it out sometime next year.
Cryptography is hard.
I prefer to say that cryptography is easy, it's the implementation of the cryptography that is fiendishly difficult. And key-management is even more difficult. (There are enough published cryptography algorithms and PRNG algorithms that are widely trusted and generally considered secure. Things generally fall apart in other areas, usually key management.)
IIRC, he talks about it again in Practical Cryptography (regarding the naivety of Applied Cryptography). I think... I've been reading both books at around the same time, so things get mixed up.
Schneier comes up a lot because he's done a very good job of bridging the gap between mere mortals and those who work on crypto systems. Books like Secrets and Lies or his CRYPTO-GRAM monthly e-mail newsletter where he explains crypto systems in plain english.
I get a kick out of reading about products in the "doghouse" in the monthly CRYPTO-GRAM.
(I know just enough about cryptography to know that I shouldn't try to roll my own...)
Without digging out my copy of Practical Cryptography, CBC also suffers the same flaw or similar flaw as ECB. It's the reason that the TrueCrypt folks switched from CBC to LRW for disk encryption. (And why tweaked CBC algorithms are popular.)
Rather then add what other posters have said... I'll leave it at this.
Go check out a copy (or purchase) of Practical Cryptography by Ferguson and Schneier. Read the first few chapters which discuss things like known-plaintext attacks, why we use block ciphers and what the estimated strength of the various algorithms are. The rest of the book gets into the nitty-gritty details, but the start of the book is suitable for anyone with more then a passing interest in crypto.
After that (or before that) you should also read Secrets and Lies which will help you to put things into perspective. Schneier does a very good job of arming the reader with the knowledge needed to make informed decisions about the process of security. Encryption is generally worthless without considering the overall picture.
As Schneier (and others) have said. Encryption is like a very sturdy pole in the ground. It's merely one part of the security system and often not even the weakest point of attack.
A rough guideline is that a 600MHz VIA C3 (fanless) is about half the processing power of a Celeron 566MHz (Pentium III core). That's based on personal experience and not anything scientific.
OTOH, that little VIA C3 system on my shelf draws a miniscule amount of power (including the 2 laptop HDDs). Makes a very good firewall PC for my home network.
(Yes, I know about the Linksys router that runs Linux. No, I don't own one. I had the VIA C3 sitting around from a previous project.)
I like to copy the text from a read receipt and then send a dozen or so messages containing that text to the sender over the next 30 minutes. : p
That sounds like a great add-in for Mozilla Thunderbird...
Get one of those case thermometers and tape the lead to the side of the drive. Maybe the SMART chip reads high on the drive, or it's not talking correctly to your motherboard.
Alternately, there's the "touch" test. If the drive feels too hot to be comfortably touched, it's too hot to live long. A well cooled drive will feel cool to the touch, even under heavy loads.
So, what HD would you use in your desktop box, if you had to replace a drive today?
I'd worry more about making sure the drive stays below 45C (or even below 40C if you can swing it). Above 45C and the drive is probably too warm to survive for long. Above 50C and it's almost certain to die an early death.
A good power-supply and good AC power (i.e. use a good server-quality UPS if your AC power is flaky) is also a good idea. I've seen perfectly good drives drop out of RAID arrays due to flaky power, causing extra rebuilds or even loss of the array if too many drop out at the same time.
Beyond that, I'd go with either 3-year or 5-year warranty products. Leaning towards the 5-year warranty drives because they (hopefully) will be of slightly better quality. All of the manufacturers with the 5-year warranty drives are about equal on quality (or lack thereof).
Remember, plan for drive failure. That drive will die and always at the worst possible time.
Most people rely so heavily on Seagate, but five year warranty is commonplace nowadays and the fact is that these drives fail as often as other major brands (more or less).
It's somewhat difficult to find a hard drive with a 5-year warranty that isn't a Seagate. For instance, looking at the 19 hard drives that are 400GB or larger at NewEgg:
(2) are 1-year warranty
(6) are 3-year warranty
(11) are 5-year warranty (2 are WD, rest are Seagate)
In that very small sample, the majority of Seagates (all?) come with 5-year warranties, while only a small portion of Western Digital's line comes with a 5-year warranty. The rest of WD's drives are either 1-year or 3-year warranty.
So for the average consumer, it's easier to say "get a Seagate" for the long warranty then it is to tell them to look at the fine print on the back of the box to figure out the warranty period.
The only brand I've had worse luck with is IBM DeskStar. Though thanks to an 100% failure rate, I no longer have any of them.
(shrugs) I bought about two dozen DeskStars over the last 8 years. Sizes were anything from 13GB up to 80GB. Probably 80-90% of them are still humming away in machines.
Most of the ones that did fail could be linked (mostly) to either poor power or poor cooling. Which, come to think of it, describes the vast majority of hard drive failures that I've seen over the past decade. Keep them cool, give them good power and they'll last near forever barring any manufacturing defects.
(There's the possible correllation that drives with manufacturing defects are more affected by poor cooling / power, thus failing sooner...)
It depends on the person's preferred method of communication. (I'm sure I'll mess up the categorizations.) Most people prefer one specific type with less preference for the others. Some folks are equally comfortable with multiple types.
Tactile? Those are the face-to-face meeting folks. They're not comfortable unless they can see you in the same room and watch the body language. They process new things by working with them in a hands-on fashion.
Visual? The e-mail and IM gods. Written is best for them. Very good readers (they tend to learn a lot from written texts).
Aural? The phone for everything folks. Or a cross-over with the face-to-face meeting folks. They are great at communicating and learning via verbal communication. These folks can repeat a conversation verbatim (or darn close).
I forget what the estimates are for the population at large for each category. But a lot of aural-centric folks simply aren't wired for communicating via e-mail / IM and have to be taught. They might come across as abrupt in written communications or leave IM conversations without saying goodbye.
Two words: top posting
I work for a company in the UK which works with a company in the States. Sometime I have to email fairly technical (ie its about source code and programming in general) messages to my counterpart in the States. To make the process as simple as possible I spend some time breaking my question(s) into pieces, numbering them, and making them clear and hopefully straight-forward. The American company practically *always* only replies to the first point in the email. If their reply addresses the problem, we still have all the others to go through, as could be seen if they'd been read at the time the first one was.
(I'm being somewhat funny, but I think it's the main reason why. If you're top-posting, then you have to scroll up/down to see the entire message that you're replying to. That or the frequent use of preview windows where you only see the upper portion of the message.)
I have a W2K system at home with only a 1/2 gig of ram and I have never, EVER, had any memory issues. And yes, I do leave my browser open for days on end.
Exactly... the reason why you never see problems is because you only have 512MB of RAM.
The primary issue with Firefox is that once you have 1GB or more, Firefox gets over-aggressive with memory use. Mostly the setting that has to do with how many previous pages are saved for each tab (window?). Below 1GB and it's set at a reasonable number, but with 1GB, suddenly the automatically configured value doubles (more?) so that Firefox goes from taking up 100MB of RAM to using 300MB of RAM.
The setting is "browser. sessionhistory. max_total_viewers" (spaces inserted to fool the Slashdot filter). The default value is -1 which allows Firefox to configure this value automatically. I've forced mine to "2" instead of the automatically configured "8".
Which keeps Firefox to a somewhat svelte 100-120MB in use (200MB peak) instead of the 300-400MB monstrosity that it was before.
Question #2: how to make an uncrashable software?
Make it so that every window runs in a separate thread so that a crash in one window doesn't affect the other windows. I'd be happier if every tab was its own thread, but a separate process for each window would work well enough.
The mozilla suite was replaced by discrete components because thats what people wanted - AND ITS WORKED.
Here's why I switched from the Mozilla Suite to Firefox + Thunderbird:
Stability
I got tired of crashes in one part of Mozilla (usually the web browser) wiping out my e-mail client at the same time. Hell, it's bad enough that Firefox, when it crashes, wipes out all of its windows instead of simply closing the affected tab (or window).
Maybe it's time to move to Opera instead... I don't even run more then 3 extensions and Firefox still dies about once a week, usually in the middle of my workday when I have 6 windows and 30 tabs open. After a while I wonder why I'm continuing to use Firefox.
About the only thing I'd use them for is a PostgreSQL xlog location (the scratch area that PostgreSQL writes to prior to committing the writes to the database). It's all sequential writes, not very high volume, but when the xlog is on the same spindle as the database you get a lot of contention and slowdown in write-heavy applications.
Even then, I'd probably replace the 5GB drive with a more modern 300GB or 400GB spindle. Create 5GB for the swap area on it, use the rest for temp directories, the xlog, and a quick-n-dirty backup location for rsync snapshots.
(Older drives are *really* slow... 5-10MB/s vs 30+ MB/s for a more modern drive. The 750GB drives do 75MB/s at the outer diameter.)
1) Performance - Average I/O time for a 4-drive RAID10 array is 1/2 that of a 2-drive RAID1 array on average. Throughput also steps somewhat linearly as you add more drives to a RAID10 array. RAID5 is fine for read-oriented storage, but not so good at writes. RAID10 allows us to improve throughput of both reads and writes.
2) Rebuild time - Rebuild time for a RAID5 array isn't all that great. And if a 2nd drive fails, you have a 100% chance of data loss (vs only a 50% chance with RAID10). There's the possibility that RAID6 would be a better fit.
For a 4-6 drive RAID, I've never been happy with RAID5 performance. Maybe it makes more sense at the 8-12 drive mark. Although at that level of spindles, you'd better be running RAID6 with hot-spares.
If this was a backup storage server, we might go the RAID6 route... in which case capacity trumps performance. (Anyone know what performance gain is on a 8 or 12 drive RAID6 array?)
Might be able to do it with an Antec Overture II case. Heat might be an issue though. Plus it takes a standard microATX motherboard.
Could put a 3:2 hot-swap SATA enclosure or a 3:2 bay cooler (80mm fan) in the front 2 5.25" bays. With one or two more drives in the rear internal 3.5" drive bay.
Still might be too large.
(We're considering using the Overture II cases as Xen head units. We don't have a real server rack, but the Overture II units are slim enough that we can pack them in tightly on a 30"x24" chrome shelf unit. Plus, since we're using Xen, we can move services between units on the fly.)