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Document Audience:
SPECTRUM
Document ID:
45222
Title:
Solstice DiskSuite[TM] - Can I create a RAID 1+0 device?
Update Date:
Tue Mar 01 00:00:00 MST 2005
Products:
Solstice DiskSuite 4.2.1 Software, Solaris Volume Manager Software
Technical Areas:
RAID (Redundant Array of Independent Disks)
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Keyword(s):1+0, 0+1, mirror, SDS, SVM, ODS, Disksuite, Solaris Volume Manager, Online Disksuite
Problem Statement
Top
None of the commands in DiskSuite or Solaris[TM] Volume Manager seem to allow the creation of a RAID 1+0 device. Can one be created using this software, and if so, how?
Resolution
Top
The short answer is: yes, RAID 1+0 metadevices can be created using DiskSuite/SVM.
Here are the details:
DiskSuite allows the user to create striped metadevices (RAID 0) of multiple physical disk partitions. It also allows the user to create mirrored metadevices of physical disk slices or striped metadevices.
To create a RAID 0+1 metadevice, one creates two striped metadevices and then one creates a mirror of these metadevices; this is standard practice with DiskSuite.
Creating a RAID 1+0 device (conceptually) requires creating multiple mirrors of disk partition pairs, then striping together the mirror metadevices.
The problem is that DiskSuite does not allow the striping of metadevices. Members of a striped metadevice must be physical disk slices, hence RAID 1+0 appears not to be possible with DiskSuite.
However, things are not always as they appear.
If the RAID 0+1 metadevice is created such that the number of columns in each of the mirrored stripes is the same, and the sizes of the physical disk slices in each column is the same, DiskSuite will internally convert that metadevice to a RAID 1+0 device. However, no difference in its outward appearance (for example, using the metastat command) will occur.
As an example, we give you what looks to be a RAID 0+1 metadevice:
d0: Mirror
Submirror 0: d10
State: Okay
Submirror 1: d20
State: Okay
Pass: 1
Read option: roundrobin (default)
Write option: parallel (default)
Size: 7058880 blocks
d10: Submirror of d0
State: Okay
Size: 7058880 blocks
Stripe 0: (interlace: 32 blocks)
Device Start Block Dbase State Reloc Hot Spare
c1t0d0s0 0 No Okay Yes
c1t1d0s0 0 No Okay Yes
c1t2d0s0 0 No Okay Yes
d20: Submirror of d0
State: Okay
Size: 7058880 blocks
Stripe 0: (interlace: 32 blocks)
Device Start Block Dbase State Reloc Hot Spare
c2t0d0s0 0 No Okay Yes
c2t1d0s0 0 No Okay Yes
c2t2d0s0 0 No Okay Yes
However, since DiskSuite treats this device as a RAID 1+0, non-corresponding disks in each submirror CAN fail without any resulting data loss. To illustrate this point, if the disks c1t0d0, c2t1d0, and c1t2d0 were all to fail, the data would still be accessible, despite the fact that all the metadevices are in a "Needs maintenance" state:
d0: Mirror
Submirror 0: d10
State: Needs maintenance
Submirror 1: d20
State: Needs maintenance
Pass: 1
Read option: roundrobin (default)
Write option: parallel (default)
Size: 7058880 blocks
d10: Submirror of d0
State: Needs maintenance
Size: 7058880 blocks
Stripe 0: (interlace: 32 blocks)
Device Start Block Dbase State Reloc Hot Spare
c1t0d0s0 0 No Maintenance Yes
c1t1d0s0 0 No Okay Yes
c1t2d0s0 0 No Maintenance Yes
d20: Submirror of d0
State: Needs maintenance
Size: 7058880 blocks
Stripe 0: (interlace: 32 blocks)
Device Start Block Dbase State Reloc Hot Spare
c2t0d0s0 0 No Okay Yes
c2t1d0s0 0 No Maintenance Yes
c2t2d0s0 0 No Okay Yes
When replacing these disks, only the disk being replaced will need to be re-synchronized. Again, that is because this metadevice is being treated by DiskSuite as a RAID 1+0 device.
If corresponding disks in each submirror were to fail (such as c1t0d0s0 and c2t0d0s0), data loss would occur |
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发表于 2010-07-03 02:26
