Re: SCSI Disk/Controller advice please
On Sat, Oct 30, 2004 at 07:10:53AM -0500, Tim Kelley wrote: On Sat, Oct 30, 2004 at 12:01:43AM +0100, Joao Clemente wrote: Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) Software raid eats up more CPU, but linux' software raid seems to be rather good. Doing the root filesystem on raid in linux is kind of a PITA. Not if you're doing a fresh install with the Sarge debian-installer CD. SW RAID-1 was downright easy. -dsr- -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
[EMAIL PROTECTED] wrote: On Sat, Oct 30, 2004 at 07:10:53AM -0500, Tim Kelley wrote: On Sat, Oct 30, 2004 at 12:01:43AM +0100, Joao Clemente wrote: Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) Software raid eats up more CPU, but linux' software raid seems to be rather good. Doing the root filesystem on raid in linux is kind of a PITA. Not if you're doing a fresh install with the Sarge debian-installer CD. SW RAID-1 was downright easy. Good news then! I was actually thinking of following the instructions on http://juerd.nl/site.plp/debianraid that installed woody on a software raid1, using knoppix to start things up and then bootstrapping woody (whatever bootstrapping means) I'll use a vmware virtual PC with 2 virtual scsi disks to try the Sarge installer CD, while I wait for the real hardware to get to my hands... Thanks for the tip! -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Mon, Nov 01, 2004 at 09:28:32AM +0800, Paolo Alexis Falcone wrote: Here's the case here - RAID 1 indeed does not mirror physical disk errors (else there's no real point in using RAID at all). However, should there be errors in the disks during reconstruction of the RAID array, RAID 1 won't save you as the errors would propagate anyway. True. RAID 5 alleviates this by using parity information stored across the disks - now it takes more than 1 disk failure for RAID 5 to fail. How does this change anything ? If you have one failed disk, and one disk containing unknown errors (the same case as your RAID1 example above), replacing the failed disk will lead to errors on the new disk. Frank -- Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. - Brian W. Kernighan -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Mon, 1 Nov 2004 15:22:17 +0100, Frank Gevaerts [EMAIL PROTECTED] wrote: On Mon, Nov 01, 2004 at 09:28:32AM +0800, Paolo Alexis Falcone wrote: RAID 5 alleviates this by using parity information stored across the disks - now it takes more than 1 disk failure for RAID 5 to fail. How does this change anything ? If you have one failed disk, and one disk containing unknown errors (the same case as your RAID1 example above), replacing the failed disk will lead to errors on the new disk. The use of parity information in separate blocks for reads and writes would just reduce the risk of that happening (prolonging the inevitable?) as data information and parity information are distributed across all disks in the array (RAID 1 won't contain parity information, and is just a copy - data and all) . The disadvantage, of course, with this setup, the controller design would be a lot more complicated and subsequently would make the array reconstruction more difficult unlike RAID 1 wherein it's guaranteed that you'd get a copy of the other half of the mirror. Whether that remaining half of the mirror already got checked for other errors that might've seeped in is another matter absent of RAID 1 though as RAID 1 doesn't have a provision for other information other than merely write data to the other disk as well. On an environment that's heavy on writes, RAID 5's overhead doesn't really justify the costs. You'd be better off with RAID 1 for that. -- Paolo Alexis Falcone [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Tue, 2004-11-02 at 00:49 +0800, Paolo Alexis Falcone wrote: On Mon, 1 Nov 2004 15:22:17 +0100, Frank Gevaerts [EMAIL PROTECTED] wrote: On Mon, Nov 01, 2004 at 09:28:32AM +0800, Paolo Alexis Falcone wrote: [snip] On an environment that's heavy on writes, RAID 5's overhead doesn't really justify the costs. You'd be better off with RAID 1 for that. Note that large-cache controllers mitigate RAID-5's write overhead. Over course, they cost more, blah blah, but when you are putting together a few TB worth of SCSI disks, RAID-5 becomes a necessity (unless you have the deepest of pockets), and so the cost of such up-scale controllers isn't so horrible. -- - Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B The difference between drunken sailors and Congressmen is that drunken sailors spend their own money. signature.asc Description: This is a digitally signed message part
Re: SCSI Disk/Controller advice please
Hi Paolo, Alvin, Pigeon, Ron Tim, thanks for all the replies... Paolo Alexis Falcone wrote: [snip] Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) [snip] Do note though that RAID 1 won't help you that much - it's better if you could try higher RAID levels (RAID 5) for data integrity. RAID 1 will only mirror disks - and that would also mean should there be errors in one disk it gets propagated to the mirror as well. Alvin, first off all I'm aware of high availability solutions (I've done my master thesis on those setups), but together with HA solutions we can use RAID anyway... Alvin and Paolo, I'm quite stunned with these claims that errors on one disk will be propagated to the other when using RAID1. It still makes no sense to me that something like that could happen. Quoting Tim: problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical Completely false. Physical disk errors mirrored by raid? No, No, No. Fat fingered deletes? Yes. Paolo, as far as I understand your statements, you state this behaviour (suposing that it does happen) does not happen with RAID5. Why? With RAID5 you checksum data and in RAID1 you mirror sectors? I've googled for these problems you claim in RAID1 and haven't found nothing stating that these things could happen! Altough I'll not be going to SCA (as it appears to add somewhat significant $$$ to my environment where I don't neet 24/7 availability), just confirm this: There is no SCA controllers. The controllers have 68 pins wich connect to the hot-swap rack (wich will also receive power from a regular power cable) and the hot-swap rack will have the sca connector to connect to a sca disk. Is that it? Thanks Joao Clemente -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
you could try higher RAID levels (RAID 5) for data integrity. RAID 1 will only mirror disks - and that would also mean should there be errors in one disk it gets propagated to the mirror as well. Indeed this is false. It also shows a complete lack of understanding the very basic principles of RAID, so please don't waste much of your time trying to figure out what the guy meant, he is seriously confused and needs to read more on RAID first. (suposing that it does happen) does not happen with RAID5. Why? With RAID5 you checksum data and in RAID1 you mirror sectors? You can detect inconsistencies in a non-degraded (and redundant) RAID regardless of RAID level (whether your RAID implementation will do it is something else entirely). RAID by itself will not be capable of detecting inconsistencies on a degraded (non-redundant) RAID. RAID does not have checksums, it has error-correction codes. You can call it parity if you wish (although that is not strictly correct, IMHO). But don't call it checksum, please. It confuses those who don't know what they are talking about in the first place. I've googled for these problems you claim in RAID1 and haven't found nothing stating that these things could happen! Because they cannot. Oh, a particular RAID1 setup could have much worse failure tolerance than another RAID5 setup, but that's all due to bad design or bad implementation on that singular RAID1 setup in the first place. just confirm this: There is no SCA controllers. The controllers have 68 pins wich connect to the hot-swap rack (wich will also receive power from a regular power cable) and the hot-swap rack will have the sca connector to connect to a sca disk. Is that it? That is correct AFAIK. -- One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie. -- The Silicon Valley Tarot Henrique Holschuh -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
On using Firewire drives for backups (was: Re: SCSI Disk/Controller advice please - fun - usb)
On Oct 30 2004, Ron Johnson wrote: On Sat, 2004-10-30 at 00:33 -0700, Alvin Oga wrote: but people still think usb hd is what they want geez... ( it's their $$$ for time and hw ) That's why I voted with my $$$ for a firewire enclosure That's what I did also: motivated by the good performance of my iPod when connected the Firewire port of my iBook both under MacOS X and under Linux and looking to be as prepared as possible in the event of crash recovery, I bought myself a Firewire enclosure for an IDE drive and a vanilla Firewire card for my Desktop. I have been quite happy with this strategy ever since. And the nice point is that current Linux kernels are able to use HFS+ quite well, which is a good compromise between a filesystem that can be used with Linux and with other OSes (it allows symlinks, which VFAT doesn't and it can be journaled, which VFAT also doesn't allow). -- Learn to quote e-mails decently at: http://pub.tsn.dk/how-to-quote.php http://learn.to/quote http://www.xs4all.nl/~sbpoley/toppost.htm -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Sun, 31 Oct 2004 15:31:03 +, Joao Clemente [EMAIL PROTECTED] wrote: Hi Paolo, Alvin, Pigeon, Ron Tim, thanks for all the replies... Paolo Alexis Falcone wrote: [snip] Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) [snip] Do note though that RAID 1 won't help you that much - it's better if you could try higher RAID levels (RAID 5) for data integrity. RAID 1 will only mirror disks - and that would also mean should there be errors in one disk it gets propagated to the mirror as well. Alvin, first off all I'm aware of high availability solutions (I've done my master thesis on those setups), but together with HA solutions we can use RAID anyway... Alvin and Paolo, I'm quite stunned with these claims that errors on one disk will be propagated to the other when using RAID1. It still makes no sense to me that something like that could happen. Quoting Tim: problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical Completely false. Physical disk errors mirrored by raid? No, No, No. Fat fingered deletes? Yes. My bad. I made a glaring misconception here. Here's the case here - RAID 1 indeed does not mirror physical disk errors (else there's no real point in using RAID at all). However, should there be errors in the disks during reconstruction of the RAID array, RAID 1 won't save you as the errors would propagate anyway. RAID 5 alleviates this by using parity information stored across the disks - now it takes more than 1 disk failure for RAID 5 to fail. Paolo, as far as I understand your statements, you state this behaviour (suposing that it does happen) does not happen with RAID5. Why? With RAID5 you checksum data and in RAID1 you mirror sectors? I've googled for these problems you claim in RAID1 and haven't found nothing stating that these things could happen! See above. The problem with RAID 5 is this - the benefits doesn't really match the costs. You get additional checking but at a very high cost (as additional space are used to store parity information, and it takes more than two disks to implement RAID 5). Some alleviate this problem by combining RAID 1 with RAID 0 as this is somehow an acceptable trade off between economics and performance. Altough I'll not be going to SCA (as it appears to add somewhat significant $$$ to my environment where I don't neet 24/7 availability), just confirm this: There is no SCA controllers. The controllers have 68 pins wich connect to the hot-swap rack (wich will also receive power from a regular power cable) and the hot-swap rack will have the sca connector to connect to a sca disk. Is that it? SCA is quite useful if you need hotswapping of SCSI disks. If that isn't the case - there's not much economic incentive in purchasing them. -- Paolo Alexis Falcone [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
On Fri, 2004-10-29 at 21:25 -0700, Alvin Oga wrote: hi ya ron On Fri, 29 Oct 2004, Ron Johnson wrote: I've been using h/w RAID for 10 years, in everything from 60GB (using scads of 4GB devices) to 15TB SANs using 147GB devices, and have *never* *ever* seen what you suggest. I would, literally, fall over dead if I ever saw that happening. good , lucky for you ... i seen people do it ... and screw up their mirrors and data Sounds like user error to me. So, what's SCA? None of these controllers says SCA... sca is the silly removable connector on the disk and in the chassis to allow oyu to remove the disk A truly uninformed statement, by someone who must not have ever needed to pull a drive out of a running system. SCA is a great and useful idea, and I wish there was something similar for internal IDE drives. since you're the expert, perhaps you can tell everybody what that connector is called that is used in the hotswap drive bays - the connector that goes on the disk - the connector that goes on the drive bay or chassis Never said I was the expert. Our SysAdmins are the experts. And they have to swap drives out of running systems on a reasonably frequent basis (it's a 24x365 data center, and there are *lots* of disks in the various SANs, NASs, direct-connect racks), and so hot plugging + SCA is very useful. and again, there is a silly equivalent thingies for IDE ... i have some - and again, on the ide drive bays, what is that connector called - but, the problem with IDE is that the ide drivers is NOT meant to hotswap and i've seen pepople pulling out disks too .. wonder why some of them call in a panic ? Yeah, I know. That's why I *wish* there was something similar for internal IDE drives. FireWire800 will be a big step in the right direction, since I can already get 1/2 of IDE speeds with my FW400 drive (an old Maxtor 60GB drive). -- - Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B Everybody today seems to be in such a terrible rush, anxious for greater developments and greater riches and so on, so that children have very little time for their parents. Parents have very little time for each other, and in the home begins the disruption of peace of the world. Mother Teresa signature.asc Description: This is a digitally signed message part
Re: SCSI Disk/Controller advice please - fun
hi ya ron On Sat, 30 Oct 2004, Ron Johnson wrote: Sounds like user error to me. yes... and/or more likely, initial system config errors .. Never said I was the expert. Our SysAdmins are the experts. :-) And they have to swap drives out of running systems on a reasonably frequent basis (it's a 24x365 data center, and there are *lots* of disks in the various SANs, NASs, direct-connect racks), and so hot plugging + SCA is very useful. if the disks are dying ... and are still under warranty .. - the disks are probably running too hot - the disks are probably a bad batch from the manufacturer - somebody dropped the box of disks during shipping one time too many - i say, disks do NOT die ... fans die 5x - 10x more often Yeah, I know. That's why I *wish* there was something similar for internal IDE drives. one should be able to fake an ide disk to look like a hot swap ide disk ... but nobody makes that connector... and i keep wondering why not it's simple ... all disks have a ready signal - missing/dead disks means drive not ready which should force the ide device driver to try again FireWire800 will be a big step in the right direction, since I can already get 1/2 of IDE speeds with my FW400 drive (an old Maxtor 60GB drive). i think firewire had its day and its dying ... usb is taking over c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
On Sat, 2004-10-30 at 00:18 -0700, Alvin Oga wrote: hi ya ron On Sat, 30 Oct 2004, Ron Johnson wrote: [snip] FireWire800 will be a big step in the right direction, since I can already get 1/2 of IDE speeds with my FW400 drive (an old Maxtor 60GB drive). i think firewire had its day and its dying ... usb is taking over Blech. USB2 HDDs are *SLOW*. -- - Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B Has there ever been a war between two democracies? signature.asc Description: This is a digitally signed message part
Re: SCSI Disk/Controller advice please - fun - usb
On Sat, 30 Oct 2004, Ron Johnson wrote: i think firewire had its day and its dying ... usb is taking over Blech. USB2 HDDs are *SLOW*. yup... almost as fast as floppies .. :-) but people still think usb hd is what they want geez... ( it's their $$$ for time and hw ) and hopefully security is a non issue, when one is allowing usb disks to be plugged in at any time c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun - usb
On Sat, 2004-10-30 at 00:33 -0700, Alvin Oga wrote: On Sat, 30 Oct 2004, Ron Johnson wrote: i think firewire had its day and its dying ... usb is taking over Blech. USB2 HDDs are *SLOW*. yup... almost as fast as floppies .. :-) but people still think usb hd is what they want geez... ( it's their $$$ for time and hw ) That's why I voted with my $$$ for a firewire enclosure and hopefully security is a non issue, when one is allowing usb disks to be plugged in at any time That's goes for any external JBOD drive. -- - Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B NAMBLA - Nat'l Assoc of Marlon Brando Look-Alikes (Yes, it's a South Park reference.) signature.asc Description: This is a digitally signed message part
Re: SCSI Disk/Controller advice please - fun - usb
On Sat, 30 Oct 2004, Ron Johnson wrote: and hopefully security is a non issue, when one is allowing usb disks to be plugged in at any time That's goes for any external JBOD drive. lot harder to hide a disk ... in ones shirt pocket and walk out :-) - cell phones with camera is no picnic either - rogue laptops sniffing your wireless traffic - another ball game for cover ones butt ( aka protect your servers ) have fun ron ... :-) dis ole boy need to get some stuff done .. c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
hi ya On Sat, 30 Oct 2004, Joao Clemente wrote: I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... there is zero point ot setting up raid-1 if you do not need to be online 24x7 Uh, no. If the data is important to you, raid1 is always the best choice. If performance, mirror two stripe (raid0) sets. problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical Completely false. Physical disk errors mirrored by raid? No, No, No. Fat fingered deletes? Yes. I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) if you insist on using raid1 ... do software raid1 so you can monitor it and maintain it whatever if you use hw raid1, you will suffer from not being able to monitor it and at the mercy of the hw vendor to provide you monitoring/maintenance tools - for the costs of the $200 hw raid1 controller, you can buy how many additional disks to do your mirroring with rsync and tar and other backup apps This is hackery, and is completely inappropriate in many situations. Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) with raid1 .. you're gonna be S.O.L if one disk dies in a bad way that will make the good disk also go bad Nonsense. -- _ _ _ _ _ _ _ _ _ _ _ _ _ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ ( t | i | m | @ | i | t | . | k | p | t | . | c | c ) \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ GPG key fingerprint = 1DEE CD9B 4808 F608 FBBF DC21 2807 D7D3 09CA 85BF -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Sat, Oct 30, 2004 at 12:01:43AM +0100, Joao Clemente wrote: Hi. For the first time I'm gonna setup a server with SCSI disks (until now I've done it only with IDE - regular ATA or SATA) I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) This server can be shutdown for maintenance at off-work hours, so I don't need any hot-plugging capability.. (this is a controller feature, right?) I'm quite confused about all the SCSI variations.. This is what I've found so far are somewhat like this: - SCSI disks, all Ultra320Wide: n Sat, Oct 30, 2004 at 12:01:43AM +0100, Joao Clemente wrote: I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) The controllers by Mylex, LSI and Adaptec all work well. Make sure it is supported by a plain vanilla linux kernel. Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) Software raid eats up more CPU, but linux' software raid seems to be rather good. Doing the root filesystem on raid in linux is kind of a PITA. This server can be shutdown for maintenance at off-work hours, so I don't need any hot-plugging capability.. (this is a controller feature, right?) Well that means you can simply buy 68 pin disks. The SCA disks are hot plug and require a backplane ($$$). - SCSI disks, all Ultra320Wide: Seagate Cheetah 10K 68 pin,36Gb - 160 EUR Fujitsu 10K 68 pin,36Gb - 150 EUR Fujitsu10K SCA/80pin, 36Gb - 150 EUR Fujitsu 15K 68 pin,18Gb - 185 EUR Fujitsu15K SCA/80pin, 18Gb - 185 EUR Ok, no problem with these... any brand/model suggestions? Any of the 68 pin drives will do. - Controllers Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: - 32 or 64bit - 160MB or Ultra320 - Raid (or not, when they say nothing.. I think) (the RAID ones start at 400 EUR and I've seen up to 950 EUR) Any u160 controller will do so long as it is supported by linux. With a two drive raid1, ultra 320 would be a complete waste of money (just two drives cannot even approach using all that bandwidth). Damn... Really confused... Please confirm these toughs also: UltraWideSCSI = 68 pin ... What is 2, 3 or 4 ?!? These seem similar to ATA 66/100/133 - the bus speed, is that it? So, what's SCA? None of these controllers says SCA... You would be looking for a hardware raid controller, with one channel, two ultra 160 68 pin disks, and an LVD 68 pin scsi cable with a terminator attached. A regular 68 pin SE cable will not do. Now raid one is really for redundancy, not performance (though it performs fine). You get best performance when separating filesystems on different sets of drive spindles. for e.g., for a webserver (in debian), you might set up /var on one raid array, and everything else on another. -- _ _ _ _ _ _ _ _ _ _ _ _ _ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ ( t | i | m | @ | i | t | . | k | p | t | . | c | c ) \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ GPG key fingerprint = 1DEE CD9B 4808 F608 FBBF DC21 2807 D7D3 09CA 85BF -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
SCSI Disk/Controller advice please
Hi. For the first time I'm gonna setup a server with SCSI disks (until now I've done it only with IDE - regular ATA or SATA) I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) This server can be shutdown for maintenance at off-work hours, so I don't need any hot-plugging capability.. (this is a controller feature, right?) I'm quite confused about all the SCSI variations.. This is what I've found so far are somewhat like this: - SCSI disks, all Ultra320Wide: Seagate Cheetah 10K 68 pin,36Gb - 160 EUR Fujitsu 10K 68 pin,36Gb - 150 EUR Fujitsu10K SCA/80pin, 36Gb - 150 EUR Fujitsu 15K 68 pin,18Gb - 185 EUR Fujitsu15K SCA/80pin, 18Gb - 185 EUR Ok, no problem with these... any brand/model suggestions? - Controllers Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: - 32 or 64bit - 160MB or Ultra320 - Raid (or not, when they say nothing.. I think) (the RAID ones start at 400 EUR and I've seen up to 950 EUR) I'm confused... none of the descriptions of the Adaptec controller I've seen state the connectors (68/80 pins)... now add more controller to the mess: Tekram PCI DC395UW - 56 EUR Tekram PCI DC390U2B - 102 EUR Tekram PCI DC390U2W Ultra 2 Low WIDE SCSI - 126 EUR Tekram PCI DC390U3W Ultra 3 WIDE SCSI 160 - 182 EUR Tekram PCI DC390U4W Ultra 4 WIDE SCSI 320 - 223 EUR Damn... Really confused... Please confirm these toughs also: UltraWideSCSI = 68 pin ... What is 2, 3 or 4 ?!? These seem similar to ATA 66/100/133 - the bus speed, is that it? So, what's SCA? None of these controllers says SCA... Any help? Ps: I supose getting a SCSI crontroller built-in on the motherboard is stupid? Those are low-value/performance controllers? Thanks Joao Clemente -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
hi ya On Sat, 30 Oct 2004, Joao Clemente wrote: I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... there is zero point ot setting up raid-1 if you do not need to be online 24x7 problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) if you insist on using raid1 ... do software raid1 so you can monitor it and maintain it if you use hw raid1, you will suffer from not being able to monitor it and at the mercy of the hw vendor to provide you monitoring/maintenance tools - for the costs of the $200 hw raid1 controller, you can buy how many additional disks to do your mirroring with rsync and tar and other backup apps Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) with raid1 .. you're gonna be S.O.L if one disk dies in a bad way that will make the good disk also go bad Seagate Cheetah 10K 68 pin,36Gb - 160 EUR you're best bet but even better if you use ide sisks ... 250GB disks for $150 or 40GB disk for $40 ... buy 4 disks ... why mirror to only 1 disk - Controllers Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: - 32 or 64bit there is zero point in plugging an expensive 64-bit controller into a 32bit slot - 160MB or Ultra320 get ultra320 if you can ... and the ribbon cable to support that speed get adapaptec ... all other scsi controllers are NOT on the radar screen - Raid (or not, when they say nothing.. I think) (the RAID ones start at 400 EUR and I've seen up to 950 EUR) for that costs.. why is it an option ... you can build 1 or 2 whole/complete systems for redundant power supply, redundant motherboard, redundant disks, redundant memory, etc, etc.. not just one disk mirrored to another disk on the same system Damn... Really confused... Please confirm these toughs also: :-) UltraWideSCSI = 68 pin ... What is 2, 3 or 4 ?!? These seem what sthe rest of the context ?? scsi-2 scsi-3 scsi-4?? ( i don't think scsi goes up that far) similar to ATA 66/100/133 - the bus speed, is that it? yeah.. maybe .. depending on where you 2 and 3 came from http://www.linux-1u.net/Disks/ata.gwif.html http://www.linux-1u.net/Disks/scsi.gwif.html So, what's SCA? None of these controllers says SCA... sca is the silly removable connector on the disk and in the chassis to allow oyu to remove the disk Ps: I supose getting a SCSI crontroller built-in on the motherboard is stupid? Those are low-value/performance controllers? onboard controllers are brain-dead and worthless but its very good for teaching why you dont want to use it vs getting an adaptec to lsi logic scsi controller if you insist on scsi c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
Hi Alvin, thanks for the quick reply. Some comments and questions, tough: Alvin Oga wrote: On Sat, 30 Oct 2004, Joao Clemente wrote: I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... there is zero point ot setting up raid-1 if you do not need to be online 24x7 ?!? What if a drive fails while on those 12h/day where people are actually using them? This will be a fileserver where documents are constantly changed/added/removed during the work hours! problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical Well, I never used it before, I tought it was somewhat smarter... like mirror UNTIL a drive goes bad. At that point stop mirroring, ignore failed drive, alert someone [...] if you insist on using raid1 ... do software raid1 so you can monitor it and maintain it if you use hw raid1, you will suffer from not being able to monitor it and at the mercy of the hw vendor to provide you monitoring/maintenance tools I see your point. Very good point! - for the costs of the $200 hw raid1 controller, you can buy how many additional disks to do your mirroring with rsync and tar and other backup apps How diferent is a every minute cronjob rsync'ing content in both drives to RAID1 (regarding the problem you stated above): bad info gets sync'ed to the good disk anyway... doesn't it? Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) with raid1 .. you're gonna be S.O.L if one disk dies in a bad way that will make the good disk also go bad A drive failure may lock the whole disk array? there is zero point in plugging an expensive 64-bit controller into a 32bit slot :-) Stupid of me for asking this one... heheheh Thanks Joao Clemente -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please - fun
hi ya On Sat, 30 Oct 2004, Joao Clemente wrote: ?!? What if a drive fails while on those 12h/day where people are actually using them? This will be a fileserver where documents are constantly changed/added/removed during the work hours! have 2 file servers ... - your fans is more likely to die than the disk - the ethernet cable will be wiggled loose while you're on vacation - when a fan dies.. you're dead ... everything will die too - when a power supply fan dies, its a matter of months before your cpu, memory, disks, power spply( days ) to all start to die ( its fun to see people wonder why their system dies when the ps ( fan is dead .. always put 3-4 extra fans in the regular midtower box - lots of ways for things to fail ... disks being the least of the problems if you bought good stuff from known-good reliable stores Well, I never used it before, I tought it was somewhat smarter... like mirror UNTIL a drive goes bad. At that point stop mirroring, ignore failed drive, alert someone data is written to disk1 ... and mirror to disk2/.. but if disk2's disk sector arrives under the head first, it is written first and mirrored to disk1 later when disk1 is not bz - it's a 2 way mirror - how does the systme know that the file is bad/corrupted, vs the file you did mean to erase on both disks ( tricky stuff ... though it can be done when one is careful ) I see your point. Very good point! sw monitoring is trivial .. monitor anything and everything till you're blue and tired of monitoring it How diferent is a every minute cronjob rsync'ing content in both drives to RAID1 (regarding the problem you stated above): bad info gets sync'ed to the good disk anyway... doesn't it? manually doing 2 way mirroring is too whacky ... and non-trivial murphy's law says your primary disk will die ... if you do 1-way mirror A drive failure may lock the whole disk array? no ... it's not supposed to when you first build the raid system .. - pull each disk out one at a time while its rwritting a 2GB file and see if survives and does finish mirroring the file its supposed to be saving - you'd be doing these test to simulate disk failures and if you spent too much time to fix it... the others in the office will say why bother with raid, it didn't work and hopefully, the bean counters willg ive you another $100 to get a new disk to put on a different pc to backup and save to a 2nd disk that probably will not fail for the same reason that the other disk died - disks doesn't die nicely, it dies abruptly and randomly - there's lots of under-utilized pc in the office to save data onto c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Sat, 30 Oct 2004 00:01:43 +0100, Joao Clemente [EMAIL PROTECTED] wrote: Hi. For the first time I'm gonna setup a server with SCSI disks (until now I've done it only with IDE - regular ATA or SATA) I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) Linux software RAID is usually good enough, but since you already invested a lot in SCSI, go for the hardware RAID. There's a recent thread in this mailing list concerning hardware vs software RAID. There are a lot of good hardware RAID cards to choose from. On a lot of enterprise machines you'd get good ones by default. Linux has quite a good sizeable roster of supported SCSI chipsets. Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) The card's custom chip does the computing on hardware raid setups, while software raid taxes the cpu for the computing. Otherwise, it's almost the same. When a disk fails, the other part in the RAID 1 (mirror) setup takes over. It'll be preferrable if you could replace the disk once it fails though - which is why hotplug is really a preferred feature. Do note though that RAID 1 won't help you that much - it's better if you could try higher RAID levels (RAID 5) for data integrity. RAID 1 will only mirror disks - and that would also mean should there be errors in one disk it gets propagated to the mirror as well. This server can be shutdown for maintenance at off-work hours, so I don't need any hot-plugging capability.. (this is a controller feature, right?) Yep. Usually hotpluggability is already built-in in a couple of SCSI RAID cards. The good thing with hotplug is that when one disk fails, you could replace it on the fly. Another thing I haven't tried is to do hotswap on Linux software raid (though I've done hotswap on hardware raid with no problems). I'm quite confused about all the SCSI variations.. This is what I've found so far are somewhat like this: - SCSI disks, all Ultra320Wide: Seagate Cheetah 10K 68 pin,36Gb - 160 EUR Fujitsu 10K 68 pin,36Gb - 150 EUR Fujitsu10K SCA/80pin, 36Gb - 150 EUR Fujitsu 15K 68 pin,18Gb - 185 EUR Fujitsu15K SCA/80pin, 18Gb - 185 EUR Ok, no problem with these... any brand/model suggestions? - Controllers Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: - 32 or 64bit - 160MB or Ultra320 - Raid (or not, when they say nothing.. I think) (the RAID ones start at 400 EUR and I've seen up to 950 EUR) I'm confused... none of the descriptions of the Adaptec controller I've seen state the connectors (68/80 pins)... now add more controller to the mess: The PCI bus has two variations - 32bit PCI (the short one found in most PCs), and the 64bit PCI (the longer ones found in servers). There's also PCI-X. You can safely guess that in terms of bus speed it goes this way: 32bit PCI 64bit PCI PCI-X. SCSI-2 disks have an 80-pin setup. SCSI-3 disks have a 68-pin setup. SCA in SCSI just integrates the data and power wires to a single attachment (hence Single Connector Attachment) Tekram PCI DC395UW - 56 EUR Tekram PCI DC390U2B - 102 EUR Tekram PCI DC390U2W Ultra 2 Low WIDE SCSI - 126 EUR Tekram PCI DC390U3W Ultra 3 WIDE SCSI 160 - 182 EUR Tekram PCI DC390U4W Ultra 4 WIDE SCSI 320 - 223 EUR Damn... Really confused... Please confirm these toughs also: UltraWideSCSI = 68 pin ... What is 2, 3 or 4 ?!? These seem similar to ATA 66/100/133 - the bus speed, is that it? So, what's SCA? None of these controllers says SCA... Ultra-Wide SCSI = SCSI-3. For the other definitions - see my post above. I think the 2/3/4 has something to do with the data rate. At any rate, to really take advantage of ultra-wide SCSI you'd need to have 64-bit PCI slots or PCI-X slots, as 32-bit PCI would cut down performance sharply. Any help? Ps: I supose getting a SCSI crontroller built-in on the motherboard is stupid? Those are low-value/performance controllers? Not all of them are low-value/performance connectors. Some are of very good quality. You could always check the chipset used and ascertain from other sources if the chipset is good enough. -- Paolo Alexis Falcone [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: SCSI Disk/Controller advice please
On Sat, Oct 30, 2004 at 12:01:43AM +0100, Joao Clemente wrote: Hi. For the first time I'm gonna setup a server with SCSI disks (until now I've done it only with IDE - regular ATA or SATA) I'm getting a completly new server (P4 3Ghz, Dual-Channel DDR 400, MB with intel chipset) and, while I have a good ideia on these components, I would like to setup a RAID-1 system with SCSI disks... I'm looking for advice on these: wich scsi controller should I buy? Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of 36GB, it is more than enough space for my setup) Adaptec are pretty good, though not the cheapest; widespread and well-supported. Would be my choice. Or Intel do some nice SCSI controllers with RAID. Tekram a bit mickey mouse IMO. Some Initio cards weren't supported in 2.6 last time I looked. Which are the tradeoffs of hard vs software raid1? What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?) Never used RAID, sorry. This server can be shutdown for maintenance at off-work hours, so I don't need any hot-plugging capability.. (this is a controller feature, right?) And the connector/mounting arrangements for the drives. SCA drives and some neat mechanism for sliding them in and locking them in. I'm quite confused about all the SCSI variations.. This is what I've found so far are somewhat like this: - SCSI disks, all Ultra320Wide: Seagate Cheetah 10K 68 pin,36Gb - 160 EUR Fujitsu 10K 68 pin,36Gb - 150 EUR Fujitsu10K SCA/80pin, 36Gb - 150 EUR Fujitsu 15K 68 pin,18Gb - 185 EUR Fujitsu15K SCA/80pin, 18Gb - 185 EUR Ok, no problem with these... any brand/model suggestions? Fujitsu. Model - that's your tradeoff of speed/capacity/price :-) - Controllers Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have: - 32 or 64bit - 160MB or Ultra320 - Raid (or not, when they say nothing.. I think) (the RAID ones start at 400 EUR and I've seen up to 950 EUR) I'm confused... none of the descriptions of the Adaptec controller I've seen state the connectors (68/80 pins)... If it says SCA it will have 80 pins. Stick the type number of the card into Google and you'll find plenty of descriptions :-) now add more controller to the mess: Tekram PCI DC395UW - 56 EUR Tekram PCI DC390U2B - 102 EUR Tekram PCI DC390U2W Ultra 2 Low WIDE SCSI - 126 EUR Tekram PCI DC390U3W Ultra 3 WIDE SCSI 160 - 182 EUR Tekram PCI DC390U4W Ultra 4 WIDE SCSI 320 - 223 EUR Damn... Really confused... Please confirm these toughs also: UltraWideSCSI = 68 pin ... What is 2, 3 or 4 ?!? These seem similar to ATA 66/100/133 - the bus speed, is that it? Yeah, pretty much. People play silly games with the ultra names, so best to look behind the ultra bit at the actual bus speed - 160, 320 etc. (figures in MHz) So, what's SCA? None of these controllers says SCA... SCA puts the power and data connections down the same cable so you only have one plug on the drive, which is handy for hot-swap racks. Ps: I supose getting a SCSI crontroller built-in on the motherboard is stupid? Those are low-value/performance controllers? Not necessarily, but it severely limits your choice both of motherboard and of SCSI controller. Remember: Google is your friend :-) -- Pigeon Be kind to pigeons Get my GPG key here: http://pgp.mit.edu:11371/pks/lookup?op=getsearch=0x21C61F7F signature.asc Description: Digital signature
Re: SCSI Disk/Controller advice please - fun
On Fri, 2004-10-29 at 16:48 -0700, Alvin Oga wrote: hi ya On Sat, 30 Oct 2004, Joao Clemente wrote: [snip] problem with raid1 ( aka mirror ) - if one disk goes bad, the other disk will copy that bad info onto the good disk the whole point of mirror, both disk is identical I've been using h/w RAID for 10 years, in everything from 60GB (using scads of 4GB devices) to 15TB SANs using 147GB devices, and have *never* *ever* seen what you suggest. I would, literally, fall over dead if I ever saw that happening. [snip] So, what's SCA? None of these controllers says SCA... sca is the silly removable connector on the disk and in the chassis to allow oyu to remove the disk A truly uninformed statement, by someone who must not have ever needed to pull a drive out of a running system. SCA is a great and useful idea, and I wish there was something similar for internal IDE drives. -- - Ron Johnson, Jr. Jefferson, LA USA PGP Key ID 8834C06B Tatoo in haste, regret in leisure. signature.asc Description: This is a digitally signed message part
Re: SCSI Disk/Controller advice please - fun
hi ya ron On Fri, 29 Oct 2004, Ron Johnson wrote: I've been using h/w RAID for 10 years, in everything from 60GB (using scads of 4GB devices) to 15TB SANs using 147GB devices, and have *never* *ever* seen what you suggest. I would, literally, fall over dead if I ever saw that happening. good , lucky for you ... i seen people do it ... and screw up their mirrors and data So, what's SCA? None of these controllers says SCA... sca is the silly removable connector on the disk and in the chassis to allow oyu to remove the disk A truly uninformed statement, by someone who must not have ever needed to pull a drive out of a running system. SCA is a great and useful idea, and I wish there was something similar for internal IDE drives. since you're the expert, perhaps you can tell everybody what that connector is called that is used in the hotswap drive bays - the connector that goes on the disk - the connector that goes on the drive bay or chassis and again, there is a silly equivalent thingies for IDE ... i have some - and again, on the ide drive bays, what is that connector called - but, the problem with IDE is that the ide drivers is NOT meant to hotswap and i've seen pepople pulling out disks too .. wonder why some of them call in a panic ? - and one can trivially do cold swap of ide disks or just buy better quality disk drives in the first place and add a silly $10 fan to keep its operating temp down ( should be about 30C or so ... ( hddtemp will tell you sorta what it is - and now days, too many vendors playing with ide cables to make it go out of spec ... from what the ide drivers can handle c ya alvin -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
