Software RAID on Linux Post: 302282630

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Operating Systems Linux Software RAID on Linux Post 302282630 by otheus on Sunday 1st of February 2009 04:39:20 AM

02-01-2009

Registered User

It seems to me that putting all the drives on one bus/SATA adaptor, is a sure way to degrade performance. I cannot answer about JFS, but another technique is to use the Logical Volume suite, which can deal with dynamically growing partitions. You can also use logical volumes for RAID 5, or you can use them for single partitions, use the "md" software raid technique to create a RAID 5 on top of those single partitions. Either way, you mount JFS on top of the create RAID device.

Quote:

I have read that there should be a significant amount of tuning to the file system and drives themselves

For IDE and slow ATA drives yes. But for S/ATA? I have not heard this.

As far as fs tuning, an optimum block size is good, and periodic defragmenting is good. For that reason, it makes sense to partition into 3 filesystems: 1 for infrequent writes, such as program images and libraries; 1 for write-mostly activity, such as for logfiles and /var activity; 1 for write-read-often, such as for configuration files and dynamic data. The first two you will rarely need to defragment. The third one you should defragment somewhat frequently. Also, you can disable atime on the first two, but can be kept on the third (IMHO).

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ataraid

ATARAID(4)						   BSD Kernel Interfaces Manual 						ATARAID(4)

NAME

     ataraid -- ATA software RAID support

SYNOPSIS

     device ata
     device ataraid

DESCRIPTION

     The ataraid driver provides support for so-called software RAID (sometimes referred to as fake RAID or pseudo RAID).

     When a controller that supports software RAID is instructed to create a RAID array, its BIOS writes data structures in a specific metadata
     format to the disks.  These data structures are picked up by the ataraid driver, so that FreeBSD can work with the array.	The ataraid driver
     has to understand the specific metadata format of a controller BIOS in order to support its RAID capabilities.

     Read-only support for a metadata format means that FreeBSD can use the given RAID array for normal read/write operations.	Creation and
     rebuild of such arrays has to be done from the controller BIOS.

     Read and write support for a metadata format means that FreeBSD can use the given RAID array for normal read/write operations.  Additionally,
     the atacontrol(8) utility can be used to create, rebuild, update and fail such RAID arrays.

     The ataraid driver can read the following metadata formats:

     o	 Adaptec HostRAID
     o	 Highpoint V2 RocketRAID
     o	 Highpoint V3 RocketRAID
     o	 Intel MatrixRAID
     o	 Integrated Technology Express (ITE)
     o	 JMicron
     o	 LSI Logic V2 MegaRAID
     o	 LSI Logic V3 MegaRAID
     o	 NVIDIA MediaShield
     o	 Promise FastTrak
     o	 Silicon Image Medley
     o	 Silicon Integrated Systems (SiS)
     o	 VIA Tech V-RAID
     o	 FreeBSD PseudoRAID

     The ataraid driver can write the following metadata formats:

     o	 Highpoint V2 RocketRAID
     o	 Intel MatrixRAID
     o	 JMicron
     o	 Promise FastTrak
     o	 Silicon Integrated Systems (SiS)
     o	 VIA Tech V-RAID
     o	 FreeBSD PseudoRAID

     It is also possible to use software RAID on controllers that do not have special software RAID capabilities.  See atacontrol(8) for details.

FILES

     /dev/ar*  ATA RAID device nodes

SEE ALSO

     ata(4), atacontrol(8)

CAVEATS

     RAID5 is not supported at this time.  Code exists, but it neither uses nor maintains parity information.

AUTHORS

     The ataraid driver was written by Soren Schmidt <sos@FreeBSD.org>.  This manual page was written by Christian Brueffer
     <brueffer@FreeBSD.org>.

BSD
								 February 17, 2006							       BSD