One of the reasons for the v1 superblock and the data offset is to provide spare space for this. For raid 5 you need three minimum hard drive disks. It is strongly recommended to use partitions stored on different hard disks to. The second problem is that with disks that size raid5 is not. Striping or mirroring two partitions on the same hard drive causes a nasty. Excellent description which also works pretty good on a 4 disk software raid 10. Home archives how to configure software raid10 in linux how to configure software raid10 in linux.
I have four drives left to configure, and i can either set them up as a raid 5 and dedicate a hot spare, or a raid 10 with no hot spare. Raid 5 with hot spare or raid 10 with no hot spare. Does windows software mirroring allow for spare readytogo hot swap as is available in raid configurations you setup an extra drive in the raid unit that lays dormant until such time as a. Lots of shops avoid hot spare on raid 10 because it forces you to lose a pair of disks of capacity because it is odd numbered and uses up a drive bay.
Four are actively used in the raid, and the fifth is a hot spare which will automatically. Replacing a failed hard drive in a software raid1 array. Bascially, if you can tolerate it, a cold spare allows you to do raid10. If that is not an acceptable scenario, then raid5 with a hot spare is the. With raid 10 you could literally have up to half the drives fail and still not lose data, as long as they arent the same mirrored drives from each raid 1 group. Raid is an acronym for redundant array of independent or inexpensive disks. Unless you wont be able to get to the server to replace a failed drive for days at a time, just keep a cold spare on a shelf. Raid 5 costs more for writeintensive applications than raid 1. Raid 0, raid 1, raid 5, raid 10 explained with diagrams. It means replacing hard disk without shutting down the server. If i install os on c and create raid 5 mirror with 3 hard drives as d on server, will. In this guide, we discuss how to use linuxs mdadm utility to manage raid arrays and perform daytoday administrative. The more complex the raid array, the more complex the software on.
It is a method of storing information on multiple hard disks for greater protection andor performance. Operating system will access raid device as a regular hard disk, no matter whether it is a software raid or hardware raid. So with rare exception, it reduces your array capacity by two bays. A hot spare, as in normal raid terminology, does not have anything to do with the extra drives present in a raid 5 or raid 6 array it is an extra drive meant to take over as soon as a drive in the array has failed. Both read and write performance usually increase, but can be hard to predict how much. This howto describes how to use software raid under linux. I expected the array to have one hot spare, namely devsdg1. Install ubuntu with software raid 10 the ubuntu live cd installer doesnt support. Explains why raid 10 is a better choice for unix linux windows. Explains why raid 10 is a better choice for unix linux windows database, mail, ms exchange, other servers. After hotadding the backup disk, the sync must be allowed to finish.
Software vs hardware raid nixcraft linux tips, hacks. For major applications ive always used at least 1 hotspare per disk drawer in all cases. You have completely overlooked the use of hot spare drives. I try and keep hard drive sizes and types limited accross servers so a spare disk can.
In my setup all of the system besides boot will reside in one raid 10 volume. Replace the hard disk identified as bad with a new, unused one. The size of each will be the same, and the raid 5 will offer enough performance. Linux provides md kernel module for software raid configuration. As a result, raid 10 offers both the great resiliency of raid 1 with the hot striping action of raid 0. My question is raid5 only requires 3 disks so if i have a 4th disk, how does that fit into the equation. Also, once reconstruction to a hotspare begins, the raid layer will start. Im raid 5 shy, but i also dont like the idea of running without a hot spare. If you have linux than you could make two raid1 and then combine them with lvm too. By using a hotspare your raid will skip the first two very important steps and then. You can optionally configure a spare for each underlying mirrored array. Im guessing that almost all shops do away with them in raid 10. If you have a hotspare, you can rebuild the array before doing this.
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