Linux software raid often called mdraid or mdraid makes the use of raid possible without a hardware raid controller. How to set up software raid 0 for windows and linux. The question is that people talk a lot on so called trel problem, such as. The softwareraid howto linux documentation project. Raid 0 was introduced by keeping only performance in mind. For this purpose, the storage media used for this hard disks, ssds and so forth are simply connected to the computer as individual drives, somewhat like the direct sata ports on the motherboard.
Software raid is one of the greatest feature in linux to protect the data from disk failure. Many hypervisors, including vmware, do not offer software. It is not possible to boot an operating system from a software raid0 or raid5. Has anybody used raid edition disks with software raid. A nonraid drive with no tler feature will respond when its ready and typically if thats longer than 30 seconds then the raid subsystem kicks the drive and you have to readd it. So a drive gets kicked out and added back again, it should be no problem. In a multiple drive software raid situation its a really bad thing. No hotswap is possible with software alone, without a hardware support. Hey, i have worked with linux for some time, but have not gotten into the specifics of hard drive tuning or software raid. Various information out there indicates software raid in linux is not concerned with hardware tlercctlerc and that the linux software raid will wait as long as the drive needs you to wait.
A curious reader recently posed this question, which ive edited to remove references to specific products and companies. From what i read, mdraid has no timeouts on its own but relies on the lower layer to timeout commands. Depends on whether the drives fire up reliably and timeout. I dont have the right setup to test this, but perhaps someone with a linux software raid could try. However, there are certain limitations of a software raid. Its a common scenario to use software raid on linux virtual machines in azure to present multiple attached data disks as a single raid device. Configure raid on loop devices and lvm over top of raid. The monthly scrub that linux md does catches these bad sectors before you have a bad time. I have a dell poweredge t105 at home and i am purcha the unix and linux forums. These will then be partitioned another block device and the partitions will be combined into a.
The exception to the rule on software raid is xlv under xfs. In the case of a failed read, raid just reads it from elsewhere and writes it back causing a sector reallocation in the drive. To setup raid 10, we need at least 4 number of disks. If you want to use software raid with sata drives on an sc1425 server with suse linux, here is the procedure. Raid will get two sectors from good and bad disks with different data. In a degraded raid for example, see this post im quoting.
Tler is supported only on hardware raid and could lead to some kind of disaster on software raid andor desktop. My disks spent their time dropping on different builds even with tler disks only. What should happen in a raid setup is that the drives give up quickly. If youre using software raid through linux like the synology units do then they are unaffected by this issue. With hardware raid cards the time before they will drop a drive from an array differs. Enabling tler only necessary with hardware raid, or. Flexibility is the key advantage of an open source software raid, like linux mdadm, but may require a specialized skillset for proper administration. As i intend to use linux software raid on centos 5, i will not have a raid controller to deal with this delegated error, but two cheap io sata controllers.
It addresses a specific version of the software raid layer, namely the 0. Linux use smartctl to check disk behind adaptec raid. As the drive is not redundant, reporting segments as failed will only increase manual intervention. A typical raid system will have several hard drives as the bottom layer. Linux software raid and zfs do not use tler and therefore are a safer choice for your data then regular hardware raid controllers. We will be publishing a series of posts on configuring different levels of raid with its software implementation in linux. In this guide, we demonstrated how to create various types of arrays using linuxs mdadm software raid utility. Find answers to do i need tler drives on raid 1 or raid10. For a home nas, a synology style linux software raid with regular data scrubbing is the peace of mind solution. Mainly with software raid systems like mdadm within linux, this software controller expects the drive to answer within 6, 7 seocnds to any of its questions. Hard drive question for linuxmdadm is erctler required.
Just wanted to write up my experiences with my raid problems. Ive spent several days reading, and i anticipate several more months before i. In a software raid configuration whether or not tler is helpful is dependent on the operating system. Here we will use both raid 0 and raid 1 to perform a raid 10 setup with minimum of 4 drives. In our earlier articles, weve seen how to setup a raid 0 and raid 1 with minimum 2 number of disks. We can use full disks, or we can use same sized partitions on different sized drives. The author is the creator of nixcraft and a seasoned sysadmin, devops engineer, and a trainer for the linux operating. Centos hard disk recomendation for a software raid 5. I remember mfenn saying that they used lots of green drives in software raid setups and they were fine, ymmv. Linux software raid and drive timeouts the ongoing struggle. References to ide and scsi have been deleted, all recent drives are sata. This is the raid layer that is the standard in linux2. Raid redundant array of inexpensive disks or drives, or redundant array of independent disks is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both.
How to check hardware raid status in linux command line replace devsg1 with your disk number. Does anybody know how linux software raid interactssupports these tler disks. In this post we will be going through the steps to configure software raid level 0 on linux. How to create a software raid 5 in linux mint ubuntu. If you are working as a linux system administrator or linux system engineer or you are already a storage engineer or you are planning to start your career in field of linux or you are preparing for any linux certification exam like rhce or you are preparing for linux admin interview then the the understanding of concept of raid become so important for you along with its. Creating software raid0 stripe on two devices using. Tler isnt going to help with linux software raid unless you need to continuosly write to the drive surveillance. What are linux scsi command timeouts and is the default. If you are going after high performance, you should be using ssds or hybrid drives, and make sure you match the performance of the drives to the performance of the bus.
The following describes the different raid levels in the context of the linux software raid implementation. So you absolutely do want tler ercetc for a hardware raid setup. In many cases hardware raid controllers are either too expensive or simply unavailablef or a particular system. It is absolutely true that this is a very important feature for hardware raid, because a hardware raid controller is probably configured to deem a hung hard drive as failed and to place it in an offline or recovery status, which has many negatives associated with it. But the real question is whether you should use a hardware raid solution or a software raid solution. If it isnt important for you then you can use desktop disks in raid. Is hardware tlercctlerc in the hddnecessary on x39. Software vs hardware raid nixcraft linux tips, hacks. Windows software raid storage space has a mixed reputation yes, a euphemism among server administrators. Is error recovery control or tler necessary for software. Linux use smartctl to check disk behind adaptec raid controllers. While theres nothing technically wrong with the storage when the raid rebuilds you eventually hit another on of these 30 second waits and another drive gets.
This is the raid layer that is the standard in linux 2. Wdc tler time limited error recovery and linux kernel. This howto describes how to use software raid under linux. Linux md will kick the drive out because as far as it is concerned its a drive that stopped responding to anything for several minutes. Software raid are available without using physical hardware those are called as software raid. Windows 8 comes with everything you need to use software raid, while the linux package mdadm is listed in most. You may still use such controllers but please test them properly but only to provide sata ports with individual disks, the raid part should be handled by linux. I used desktop disks in raid and sometimes my operating system went to the kernel panic state. Is this true and i shouldnt use these drives or its just bla. Its really a feature designed to prevent long retries causing a hardware raid controller to chuck a disk out of a set whereas most nass use mdadm, which is a software raid controller, but even though the nas will not chuck a disk after a few seconds, the tler is still useful in that it will prevent a disk suffering an unrecoverable read. Raid can be created, if there are minimum 2 number of disk connected to a raid controller and make a logical volume or more drives can be added in an array according to defined raid levels. Raidlinear is a simple concatenation of partitions to create a larger virtual partition.
Linux raid is different from windows for sound technical. It is handy if you have a number small drives, and wish to create a single, large partition. Only you can assign bad disk as bad after this situation. Lastly i hope the steps from the article to configure software raid 0 array on linux was helpful.
How important is tler, erc, cctl, etc on a synology nas. Tler is mostly important when you have a hardware raid controller. This section will mention some of the hardware concerns involved when running software raid. The disk timeout is usually configured to trigger before the os timeout or hw raid controller, so that the latter knows what really happened instead of just waiting and aborting. A raid can be deployed using both software and hardware. Not to mention the performance hit under heavy io not having a dedicated hardware controller handling all the striping and parity operations. I have seen some of the environments are configured with software raid and lvm volume groups are built using raid devices. What are linux scsi command timeouts and is the default suited for software raid. There are many howtos available on the internet that describe several different schemes for utilizing linux software raid to provide mirroring of boot, root, and even other partitions. So you absolutely do want tlerercetc for a hardware raid setup. If youre using software raid like linux mdraid, it probably doesnt matter. Linux file systems are generally fragile enough without throwing software raid and questionable hardware into the mix.
Linux uses either the mdraid or lvm for a software raid. Im so much of a newbie that i cant even rent a clue as to the best distro for my intention. Western digital timelimited error recovery tler with. Raid 10 is a combine of raid 0 and raid 1 to form a raid 10. A redundant array of inexpensive disks raid allows high levels of storage reliability. How to set up software raid 0 for windows and linux pc gamer.
Without a hardware raid controller or a software raid implementation to drop the disk, normal no tler recovery ability is most stable. Moving from windoze hardware raid to linux software raid. Linux software raid and bsd software raid, including zfs, is a lot smarter and should never get your brokensplit arrays, but rather configurable recovery time. We just need to remember that the smallest of the hdds or partitions dictates the arrays capacity. I have four of the western digital caviar se16 500 gb wd5000aaks 16 mb sataii 300 mbs hard drive models.
632 1128 650 1180 630 28 625 334 325 1343 745 1356 287 41 563 1202 884 508 623 781 1139 811 409 1500 823 839 7 535 940 248 953 551 937 581 923 1409 332