Hey Jijo! Long time no hear. :D Actually, the IBM person who services us recommended raid 5 and proceeded to configure the servers for us. hehehe! After this only 4 drives are read by the IBM SCSI manager as 1 logical drive while the other 1 drive is considered swap drive. *scratches head*
Does this mean 4 drives are doing the parity thing of raid 5 while the 5th one is ready for swapping? Sabi lang kasi ng IBM tech ready for failover na yan. Medyo takot lang ako kasi hindi ako yung gumawa ng raid. :D If something happens tapos hindi ikaw yung tumira parang kabado ka di ba. Nangyari na kasi dati IBM tech din yung nag configure ng raid 5 test server namin tapos 1 drive failed, hinugot ko para palitan... nag-crash yung control... parang nalito yung controller. hehehe. I had to rebuild linux install again. The tech guy had to come back and flash the scsi controller. So I was wondering why it didn't work for me when I tried hot swapping it. Baka may tama lang yung scsi controller? Ok so tama ba ganito? Basta raid 5 hot swappable yung scsi I can just remove the drive and replace it? Thanks. fritz <www.mesedilla.com> --- + Basta Ikaw Lord > -----Original Message----- > From: Federico Sevilla III [mailto:[EMAIL PROTECTED] > Sent: Thursday, September 11, 2003 11:42 AM > To: Philippine Linux Users Group Mailing List > Subject: Re: [plug] raid 5 > > > On Thu, Sep 11, 2003 at 11:24:59AM +0800, Fritz Mesedilla wrote: > > How does raid work? > > > > I saw this http://www.acnc.com/04_01_05_flash.html > > Doesn't that URL explain the various RAID levels to you well enough? > It's a pretty comprehensive summary of the various RAID levels. :) > > > And it said "Difficult to rebuild in the event of a disk failure (as > > compared to RAID level 1)" > > You're probably comparing RAID 1 with RAID 5. Obviously, it's much > easier to rebuild RAID 1, which does plain mirroring. When one drive > dies, the other drive has a complete copy and you can operate > fully with > it. When you replace the disk, the copies are mirrored onto it and > you're back with your redundancy. > > With RAID 5 you have the parity bits spread out across your drives. > Let's take a minimum scenario, where you have three drives. When one > drive dies, you run in degraded mode where both active drives use the > parity information to "simulate" the existence of the third drive. If > another drive dies, you're dead. Things also slow down, since your > drives work overtime to cover up for your missing drive. > > In case it isn't obvious yet, RAID 5 needs more drives than > RAID 1 (RAID > 1 can be implemented with a minimum of two drives, RAID 5 > needs at least > three), but "wastes" less space. > > > How does one recover from a raid 5 disk failure? Can I just remove > > the defective drive while the server is running and "insert" a new > > one? (hot-swap) > > > > Will it automatically recover itself? > > When you replace the damaged disk, you instruct your controller to > rebuild the array. It will use the parity information on the surviving > drives to rebuild the data on the third. When the rebuild is complete, > you will run in normal mode and the speed penalty of running > in degraded > mode will disappear. In typical operation you will not lose any data. > > > From what I knew before... if I have 5 scsi drives, 4 are > used while 1 > > is used in case of disk failure. > > This really depends on you. Assuming you're talking about > RAID 5 (note, > we're talking about RAID levels, not number of drives), the parity > information is spread out across all your drives. You can have five > active drives in RAID 5, AFAIK, since it doesn't require an > even number > of drives to operate. Alternatively, you can have a four-drive RAID 5 > array, with one drive allocated as a hot-swap drive. A hot-swap is > activated to replace a faulty drive as soon as that faulty drive goes > offline. This reduces the time that your array operates in degraded > mode, since it rebuilds the array using the hot-swap as soon as the > defective drive goes down. > > What do you plan to use your RAID array for? Depending on your > forecasted loads, storage needs and budget, you may want to > look at RAID > 10 instead of RAID 5. RAID 10 is faster than RAID 5 because it doesn't > have the overhead of parity calculation and storage. It benefits from > the striping of the mirrored pairs, which further improves > both read and > write speeds. RAID 10 is also more fault tolerant than RAID > 5. On a good > day, a four-drive RAID 10 array can withstand two downed drives, > assuming of course that they don't belong to the same mirrored pair. > > --> Jijo > > -- > Federico Sevilla III : http://jijo.free.net.ph : When > we speak of free > Network Administrator : The Leather Collection, Inc. : > software we refer to > GnuPG Key ID : 0x93B746BE : > freedom, not price. > -- > Philippine Linux Users' Group (PLUG) Mailing List > [EMAIL PROTECTED] (#PLUG @ irc.free.net.ph) > Official Website: http://plug.linux.org.ph > Searchable Archives: http://marc.free.net.ph > . > To leave, go to http://lists.q-linux.com/mailman/listinfo/plug > . > Are you a Linux newbie? To join the newbie list, go to > http://lists.q-linux.com/mailman/listinfo/ph-linux-newbie > ---------------------------------------------------------------------- This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. 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