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Adaptec 2410SA SATA Raid 5 : is it a safe choice
I intend to build a small server for my (6 Win XP computers) home LAN, to
backup my Data (and store some original documents). Adaptec 2410SA Serial ATA Raid card seems to be a nice choice in terms of price : you can use 4 cheap disks in Raid 5 mode to "secure" a capacity of 3. If I understood correctly, if ONE disk crashes, it's quit easy to "rebuilt" its content with the parity data. Specially if a 24/7 capacity is not that important... I never built any Raid, so it's quite difficult for me to understand wether it's a good choice in terms of real security for my data : what happens if there is a "general" crash of the server (accidental reboot, no more AC, controler Card burning...). Will I loose ALL the data of the array ? Has the system a capacity to recover at least a part of data ? And is the Adaptec 2410SA reliable ? Hard AND soft ? More than the (cheaper) Promise FastTrak S150 SX4 ? Should it be better (and easier to build) to boot the PC from another disk (I've got some small capacity disks in my drawer...) and not from the Raid Array ? Please help a newbie for a good choice... |
#2
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Toto wrote:
Adaptec 2410SA Serial ATA Raid card seems to be a nice choice in terms of price : you can use 4 cheap disks in Raid 5 mode to "secure" a capacity of 3. If I understood correctly, if ONE disk crashes, it's quit easy to "rebuilt" its content with the parity data. Specially if a 24/7 capacity is not that important... I never built any Raid, so it's quite difficult for me to understand wether it's a good choice in terms of real security for my data : what happens if there is a "general" crash of the server (accidental reboot, no more AC, controler Card burning...). Will I loose ALL the data of the array ? Has the system a capacity to recover at least a part of data ? And is the Adaptec 2410SA reliable ? Hard AND soft ? More than the (cheaper) Promise FastTrak S150 SX4 ? Should it be better (and easier to build) to boot the PC from another disk (I've got some small capacity disks in my drawer...) and not from the Raid Array ? I run the smaller brother of the 2410SA with two disks in a mirror (RAID 1) config for a smiliar purpose. It does provide some fault tolerance, but it is not a perfect solution. There are a few things you should note: - The system can only take a fault on one of the disks, i.e. if the 2nd disk crashes before you replace the faulty one, your data is lost - The layout doesn't help against power spikes and such, which can fry all of the disks - the layout doesn't help against logical errors, such as corrupted filesystems The exerience with the Adaptec controller has been good, albeit the cables they supplied are a bit loose. There is a web-based administration tool for the RAID software as well as CLI solution. Because my controller only does two disks, it doesn't have RAID5 capability, but I don't see why it should be a major problem. I think what you are proposing is a reasonably safe way to store documents at home, but you should also think about some off-line reserve, such as a DVD burner, where you can dump stuff once in a while (this is what I do). Also some small UPS or at least a surge protection on the power supply could decrease the chances of electrical failures. BTW, with modern 250 or 300GB disks, you could see if a mirror config with a hot spare would be a good option. It would give you over 0.5TH capacity and be a more resiliant to single disk failures (i.e my first note will decrease in inportance). Marcin |
#3
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Toto,
I intend to build a small server for my (6 Win XP computers) home LAN, to backup my Data (and store some original documents). Adaptec 2410SA Serial ATA Raid card seems to be a nice choice in terms of price : you can use 4 cheap disks in Raid 5 mode to "secure" a capacity of 3. If I understood correctly, if ONE disk crashes, it's quit easy to "rebuilt" its content with the parity data. Specially if a 24/7 capacity is not that important... I never built any Raid, so it's quite difficult for me to understand wether it's a good choice in terms of real security for my data : what happens if there is a "general" crash of the server (accidental reboot, no more AC, controler Card burning...). Will I loose ALL the data of the array ? Has the system a capacity to recover at least a part of data ? And is the Adaptec 2410SA reliable ? Hard AND soft ? More than the (cheaper) Promise FastTrak S150 SX4 ? Should it be better (and easier to build) to boot the PC from another disk (I've got some small capacity disks in my drawer...) and not from the Raid Array ? Have you ever thought about implementing a simple SW-Raid5? The cpu overhead of such an solution would probabaly be minimal, because file servers never tend to run out of cpu cycles anyway. I'd implement a software raid, this would safe you 400+US$ (for the SATA Controller) which you can spend on 4 additonal [SP]ATA drivers. Most OSes include a software RAID5 driver for use with the system. I'd personally go for 6 cheap SATA ports (without any RAID), 6x160GB drives which offer the best bang for the buck (640GB of available space), configured as raid5 with a hotspare option. As a host OS I'd opt for Linux plus Samba for providing FileServies for the Windows systems. All of his attached to a cheap 8+port 100Mbit switch with decent NICs and you're ready to roll (and can expect the system to completely saturate the 100MBit LAN interface without encountering any other bottleneck). The total (storage only) solution would probably cost around 600-650US$ That's 550$ for the disks plus three cheap SATA controllers for 30$ each (probably SIL3112 or SIL3114 based), plus the computer itself. Regarding Adaptec, we only use SCSI RAID Adapters, which have some nice features, but mostly lack performance. If you want peformance in SCSI, the best option will probably be lsilogic - I'd assume that this is also true for SATA, but am happy to be proven wrong (at least in this point). Just my 2 cents, Jochen |
#4
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Jochen Kaiser wrote in news:cia0ek
: Have you ever thought about implementing a simple SW-Raid5? I must say I didn't, and what you explain sounds quite interesting. Just two questions : - I am not (already) a Linux user, despite all the good things I think of it. But as none of my friends uses it (and could help me), I've always been waiting for a "quieter" moment to try it... and it never came... Do you think a simple SW-Raid5 shoud be a good solution too under Windows ? And if not, is it possible for a Linux newbie to build such a server ? - what minimum CPU should be enough for what you suggest... I've some "half old" mainboards (such as with Athlon 1800 +) that could be used if they match the minimum requirements... Thanks anyway for your answer... |
#5
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Marcin Dobrucki wrote in news:fGU1d.25394
: It would give you over 0.5TH capacity and be a more resiliant to single disk failures Understand your suggestions... Even if a 4 disks Raid 5 would give me, if I'm correct, 0.75th... I must consider this solution anyway... Thanks a lot... |
#6
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Hello,
I must say I didn't, and what you explain sounds quite interesting. Just two questions : - I am not (already) a Linux user, despite all the good things I think of it. But as none of my friends uses it (and could help me), I've always been waiting for a "quieter" moment to try it... and it never came... Do you think a simple SW-Raid5 shoud be a good solution too under Windows ? And if not, is it possible for a Linux newbie to build such a server ? === Possible yes, but I would definitely not recommend it. If your run into trouble with ill-supported hardware, the debugging will be very difficult to handle for a newbie. Windows NT4,2k[and 3] server contain sofware raid0/1/5 software (actually a thinned down version of veritas' VxVM). Windows however cannot boot on a raid5 (this would require windows to load the raid driver before the OS), but should be able to boot from Raid1 (or at least boot from one of the mirrors). My best bet in this case would be to setup two small disks (I think you mentioned some) to act as a mirrored boot driver, with 2+GB each. Mirror or duplex them (the latter is a mirror using two separet controllers, which would survive the loss of one controller) and include 3 or more disks as a software raid5. As you can see it can be done, but it would require the server variant of windows. - what minimum CPU should be enough for what you suggest... I've some "half old" mainboards (such as with Athlon 1800 +) that could be used if they match the minimum requirements... === I'd spec the minimum requirements for a windows based solution on something like 600-800Mhz and 192+MB RAM. So, yes such an Athlon would be more than sufficient. HTH, Jochen |
#7
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Using the Adaptec RAID adapter is a scary proposition. In the event of a
server failure the only way to ensure the integrity of your data is have battery backed up cache. Otherwaise, any data that resides in cache that has not yet commited to disk would be lost. One big piece of advice is to try to avoid the temptation of using large capacity ATA disk as the rebuild time would be lengthy and exposes you to the potential of total data loss since you are running in degraded mode for a longer period of time. Try using external RAID as the levels of redundancy are way better "Toto" wrote in message ... I intend to build a small server for my (6 Win XP computers) home LAN, to backup my Data (and store some original documents). Adaptec 2410SA Serial ATA Raid card seems to be a nice choice in terms of price : you can use 4 cheap disks in Raid 5 mode to "secure" a capacity of 3. If I understood correctly, if ONE disk crashes, it's quit easy to "rebuilt" its content with the parity data. Specially if a 24/7 capacity is not that important... I never built any Raid, so it's quite difficult for me to understand wether it's a good choice in terms of real security for my data : what happens if there is a "general" crash of the server (accidental reboot, no more AC, controler Card burning...). Will I loose ALL the data of the array ? Has the system a capacity to recover at least a part of data ? And is the Adaptec 2410SA reliable ? Hard AND soft ? More than the (cheaper) Promise FastTrak S150 SX4 ? Should it be better (and easier to build) to boot the PC from another disk (I've got some small capacity disks in my drawer...) and not from the Raid Array ? Please help a newbie for a good choice... |
#8
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"Monte Oates" wrote in message news:1o55d.93585$%S.85565@pd7tw2no... Using the Adaptec RAID adapter is a scary proposition. Only to the incompetent. In the event of a server failure the only way to ensure the integrity of your data is have battery backed up cache. The only way to ensure that the data held at that instant in the cache(could be none) is not lost is to have some sort of battery support. A UPS is often sufficient. Losing some data in the cache does NOT mean that you have lost all integrity...just a small amout of the most recent data. Otherwaise, any data that resides in cache that has not yet commited to disk would be lost. One big piece of advice is to try to avoid the temptation of using large capacity ATA disk One big piece of advice is avoid this guy's advice. as the rebuild time would be lengthy and exposes you to the potential of total data loss since you are running in degraded mode for a longer period of time. That's utterly ridiculous. There's nothing special about ATA as the same applies to a SCSI array. The window of vulnerability you describe has a very small risk. Ever hear of hot spare? Evere hear of big SCSI HDs? Ever hear of small ATA HD? Try using external RAID as the levels of redundancy are way better Pure trash especially when a price performance analysis is done? "Toto" wrote in message ... I intend to build a small server for my (6 Win XP computers) home LAN, to backup my Data (and store some original documents). Adaptec 2410SA Serial ATA Raid card seems to be a nice choice in terms of price : you can use 4 cheap disks in Raid 5 mode to "secure" a capacity of 3. If I understood correctly, if ONE disk crashes, it's quit easy to "rebuilt" its content with the parity data. Specially if a 24/7 capacity is not that important... I never built any Raid, so it's quite difficult for me to understand wether it's a good choice in terms of real security for my data : what happens if there is a "general" crash of the server (accidental reboot, no more AC, controler Card burning...). Will I loose ALL the data of the array ? Has the system a capacity to recover at least a part of data ? And is the Adaptec 2410SA reliable ? Hard AND soft ? More than the (cheaper) Promise FastTrak S150 SX4 ? Should it be better (and easier to build) to boot the PC from another disk (I've got some small capacity disks in my drawer...) and not from the Raid Array ? Please help a newbie for a good choice... |
#9
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On Sat, 25 Sep 2004 03:30:25 GMT, "Ron Reaugh"
wrote: "Monte Oates" wrote in message news:1o55d.93585$%S.85565@pd7tw2no... Using the Adaptec RAID adapter is a scary proposition. Only to the incompetent. Like, say, Ron... In the event of a server failure the only way to ensure the integrity of your data is have battery backed up cache. Toto, the following is why ignoring this Ron "character" is good advice: The only way to ensure that the data held at that instant in the cache(could be none) is not lost is to have some sort of battery support. A UPS is often sufficient. Losing some data in the cache does NOT mean that you have lost all integrity...just a small amout of the most recent data. Or, quite likely, a small amount of the most recent *meta*data. Ron lacks any kind of system-level knowledge or understanding, and so doesn't understand that if your filesystem believes that, say, some part of the space allocation mechanisms (File Allocation Table, for example) has been updated, but due to a controller trick it was not actually updated (merely scheduled for update, and then lost as a result of power fail), you'll end up with (e.g.) a file that occupies sectors that are also marked as free. The next file that gets created may the overwrite your data in another file, and you won't know about it until later. This is usually considered bad. Based on length observation, Ron never seems to deal with systems where it actually matters... Malc. |
#10
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"Malcolm Weir" wrote in message Ron lacks any kind of system-level knowledge or understanding, and so doesn't understand that if your filesystem believes that, say, some part of the space allocation mechanisms (File Allocation Table, for example) has been updated, but due to a controller trick it was not actually updated (merely scheduled for update, and then lost as a result of power fail), you'll end up with (e.g.) a file that occupies sectors that are also marked as free. The next file that gets created may the overwrite your data in another file, and you won't know about it until later. This wacko runs around drumin expensive RAID solutions based on wild rantings about dooms day scenarios. While such situations may under some circumstances be possible their likelihood is vanishing. A UPS covers the issue and a UPS is a good idea for critical systems for a number of reasons. Ignore this frequently refuted wacko. This is usually considered bad. Based on length observation, Ron never seems to deal with systems where it actually matters... Reality check time. |
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