ganesh029
1 Copper

raid 5 device

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2-way mirror device occupies 2 mirror position, 3-way mirror occupies 3 mirror positions, 4 -way mirror occupies 4 mirror positions but cant comprehend raid-5 occupying m1 and m2 positons since its in effect pointing to the same disks without any extra copy in the actual volume.....

Thanks in advance

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mbresnahan
3 Argentium

Re: raid 5 device

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Some background info, with RAID 5 on DMX-3/4 (pre-VMAX)  the M1 position is used for marking data tracks valid/invalid, and the M2 is for the parity tracks.  Of course, both data and parity tracks are striped across all members of the group, so it's not quite the same as RAID 1 which has one mirror position for each drive in the group (again, talking pre-VMAX).

*I'm an Inlines guy, hope this answers more questions than it creates

Mike

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Quincy561
4 Tellurium

Re: raid 5 device

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Correct, it doesn't make obvious sense.  AFAIK, the mirror positions were used to track if the raid group had invalid tracks or not.  

On VMAX all raid types occupy one mirror position, including 3 and 4 way mirror (which I've never actually seen used in real life)

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ganesh029
1 Copper

Re: raid 5 device

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Is it possible to make it more elaborate?

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Quincy561
4 Tellurium

Re: raid 5 device

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On DMX, each local RAID 1 mirror takes one mirror position.  Each local RAID5 3+1 and RAID5 7+1 volume uses two mirror positions.  Each local RAID6 6+2 and RAID6 14+1 volume uses just one mirror position.  Is that more elaborate?

ganesh029
1 Copper

Re: raid 5 device

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yes....  thanks a ton....

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SKT2
4 Tellurium

Re: raid 5 device

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I can list devices by the different raid level such as `symdev list -raid5` or `symdev list -raid1`. I can even get the list for raid 5 by `-protection 3+1` or `-protection 7+1`.

When i list with  `-raid1` how can i confirm if the device is actually RAID1 or RAID0+1 or RAID1+0(?). OR do i have to make a guess with what raid levels are supported on each models( my case DMX-24/5733)

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beetgj
1 Copper

Re: raid 5 device

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The output of your symdev list -raid1 will only display 2-way mirrored volumes

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mbresnahan
3 Argentium

Re: raid 5 device

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Some background info, with RAID 5 on DMX-3/4 (pre-VMAX)  the M1 position is used for marking data tracks valid/invalid, and the M2 is for the parity tracks.  Of course, both data and parity tracks are striped across all members of the group, so it's not quite the same as RAID 1 which has one mirror position for each drive in the group (again, talking pre-VMAX).

*I'm an Inlines guy, hope this answers more questions than it creates

Mike

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