How many data is written?

Question

Hi all, I'm struggling with calculating a RAID5 set on a symmetrix. EMC has deployed our Symmetrix with hypers of the kind RAID5 (7datadisks + 1paritydisk ). I'm trying figure out how many data is written on each of the data disks in this RAID5 set. This is what I can come up with at the moment: Partial Output of symdev command: Device Block Size 512B Device Capacity       {        Cylinders            :      14788       Tracks               :     221820       512-byte Blocks      :   28392960       MegaBytes            :      13864       KiloBytes            :   14196480       } Geometry             : Native        {         Sectors/Track        :        128        Tracks/Cylinder      :         15        Cylinders            :      14788        512-byte Blocks      :   28392960        MegaBytes            :      13864        KiloBytes            :   14196480        } RAID-5 Device Information       {        Number of Tracks in a Stripe                : 4       Overall Ready State of RAID-5 Device        : Ready       Overall WriteProtect State of RAID-5 Device : Enabled       Member Number of the Failing Device         : None       Member Number that Invoked the Spare        : None       Disk Director (DA) that Owns the Spare      : None       Copy Direction                              : N/A       RAID-5 Hyper Devices (7+1):           {            Device : 10BD               {                --------------------------------------------------------------                Disk     DA       Hyper       Member    Spare       Disk               DA :IT   Vol#   Num Cap(MB)  Num Status  Status  Grp#  Cap(MB)               --------------------------------------------------------------               12B:D1    903    47    1984    1 RW      N/A        3   286102               05D:C1     47    47    1984    2 RW      N/A        3   286102               05A:D1   1116    47    1984    3 RW      N/A        3   286102               12C:C1     47    47    1984    4 RW      N/A        3   286102               05B:C1     47    47    1984    5 RW      N/A        3   286102               12D:D1   1042    47    1984    6 RW      N/A        3   286102               12A:C1     47    47    1984    7 RW      N/A        3   286102               05C:D1   1042    47    1984    8 RW      N/A        3   286102               } If my calculations are correct the Track size is 64kB. With a stripe size of 4 tracks, I get a 256kB stripe size that is written over 7 data disks. The data that is written to each member of the data disks would be 36.57kB. I find this a very odd number. Can someone verify the calculation?? Please! Message was edited by: mamer [added 'tracks' to clarify calculation]

Quincy561 · Accepted Answer

There are 4 64k tracks on each data disk, and then 4 64k tracks on the parity to protect the data.  The parity is rotated. Here is a picture of 3+1, 7+1 is the same except there are more data members.

mamer1 · Answer

thx. This clears everything up.

Symmetrix

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