Hi All,
This is neto from Brazil
How are you?
Using mathematics is not hard to show that 1=2. This is called fallacy where an incorrect result arrived at by apparently correct, though actually specious reasoning.
The most common example of a mathematical fallacy is the "proof" that 
as follows. Let 
, then
The incorrect step is in which division by zero (
) is performed, which is not an allowed algebraic operation. Similarly flawed reasoning can be used to show that 
, or for example that (EMC Snapshot = NetApp Snapshot) AND (Other Vendors RAID 6 = NetApp RAID 6 (RAID DP)) .
RAID 6: EMC versus NetApp
Microsoft Storage Technology (Exchange 2007)
Traditional RAID 6
"RAID-6 adds an additional parity block and provides approximately double the data protection over RAID-5, but at a cost of even lower write performance. As physical disks grow larger, and consequently RAID rebuild times grow longer, in some cases RAID-6 is necessary to prevent logical unit number (LUN) failure if an uncorrectable error occurs during the rebuild, or if a second disk in the array group fails during rebuild. Due to disk capacity, some vendors support RAID-6 instead of RAID-5"
NetApp RAID 6 (RAID-DP)
"RAID-DP from NetApp is a proprietary implementation of RAID double parity for data protection. RAID-DP falls within the Storage Network Industry Association definition of RAID-6. RAID-DP is also a trademark of NetApp.
Unlike traditional RAID-6, RAID-DP utilizes diagonal parity using two dedicated parity disks in the RAID group. RAID-DP is also similar to other RAID-6 implementations in terms of the reliability metrics and its ability to survive the loss of any two disks; however, a third disk failure will result in data loss. Whereas current RAID-6 implementations incur an I/O performance penalty as a result of introducing an additional parity block, RAID-DP is optimized in terms of reducing read I/Os due to the way the NetApp controller handles parity write operations. Unlike other storage controllers that write changes to the original location, the NetApp controller always writes data to new blocks, thus making random writes appear to be written sequentially. It is important to follow NetApp best practices for sizing the array to ensure a consistent level of performance for Exchange implementations"
Snapshot: EMC versus NetApp
EMC - Performance tests (SnapView™ enabled)
NetApp - Performance tests (Snapshot™enabled)
Another example that I did on my lab:
mickey - Oracle Enterprise Linux 4
pernalonga (Bugs Bunny) - NetApp Storage
Data: 100GB - Oracle Data
Oracle Backup: SnapManager for Oracle
Workload: Swingbench - Swingbench 2.3.0.385 - Benchmark "Order Entry (PLSQL)"
Performance impact: NO
Time to execute backup (NetApp Snapshot): 34 seconds
If you think that (EMC Snapshot = NetApp Snapshot) AND (Other Vendors RAID 6 = NetApp RAID 6 (RAID DP)) this is a perfect example of fallacy
Technically speaking or writing, 1 is different from 2
So 0 (EMC) is different from 1 (NetApp).
If you choose EMC, you can have a similar error:
EMC PANIC: exception encountered: core dump [kpopfr () +673] [SIGFPE] [EMC Snapshot - division by zero] [0x4000000001EB4AE1]
Exception signal: 8 (SIGFPE), code: 1 (EMC Snapshot - division by zero), addr: 0x4000000001eb4ae1, PC: [0x4000000001eb4ae1, kpopfr () +673]
r1: 60000000000a8128 r20: 9fffffff7fbaa744 br5: 0 r1: 60000000000a8128 r20: 9fffffff7fbaa744 br5: 0
r2: 0 r21: 46e0 br6: c00000000033a6f0 r2: 0 r21: 46e0 br6: c00000000033a6f0
r3: 1825d r22: 9fffffff7fba60a0 br7: e0000000014a17e0 r3: 1825d r22: 9fffffff7fba60a0 br7: e0000000014a17e0
r4: 0 r23: 0 ip: 4000000001eb4ae1 r4: 0 r23: 0 ip: 4000000001eb4ae1
r5: c000000000000408 r24: 42222008 iipa: c000000450ec02e0 r5: c000000000000408 r24: 42222008 iipa: c000000450ec02e0
r6: c0000000000500e0 r25: 0 cfm: 8 r6: c0000000000500e0 r25: 0 cfm: 8
r7: 9fffffff7fff8e48 r26: 6e40 um: 1a r7: 9fffffff7fff8e48 r26: 6e40 um: 1a
r8: 100000000 r27: 6000000000232ab1 rsc: 1f r8: 100000000 r27: 6000000000232ab1 rsc: 1f
r9: 2000000 r28: 37485637f bsp: 9fffffff7ffffd58 r9: 2000000 r28: 37485637f bsp: 9fffffff7ffffd58
r10: 9fffffff7fbaa784 r29: 22c24 bspstore: 9fffffff7ffffd58 r10: 9fffffff7fbaa784 r29: 22c24 bspstore: 9fffffff7ffffd58
r11: 0 r30: c00000048b338dd8 rnat: 4000000002dc7660 r11: 0 r30: c00000048b338dd8 rnat: 4000000002dc7660
r12: 9fffffffffff73e0 r31: c000000000001028 ccv: 0 r12: 9fffffffffff73e0 r31: c000000000001028 ccv: 0
r13: 9fffffff7fc65420 NaTs: 0 unat: 0 r13: 9fffffff7fc65420 NaTs: 0 unat: 0
r14: 0 PRs: 183d3 fpsr: 9804c8a74433f r14: 0 PRs: 183d3 fpsr: 9804c8a74433f
r15: 0 br0: 4000000001eb8700 pfs: c00000000000099b r15: 0 br0: 4000000001eb8700 pfs: c00000000000099b
r16: 600000000003ffd0 br1: 400000000b63cd70 lc: 0 r16: 600000000003ffd0 br1: 400000000b63cd70 lc: 0
r17: 9fffffffffff7480 br2: 0 ec: 0 r17: 9fffffffffff7480 br2: 0 ec: 0
r18: 46e4 br3: 0 isr: 9fffffff7ffffd58 r18: 46e4 br3: 0 isr: 9fffffff7ffffd58
r19: 46a4 br4: 0 ifa: c00000047352e180 r19: 46a4 br4: 0 ifa: c00000047352e180
Reason code: 002c Reason code: 002c
*** 2008-02-26 10:10:30.972 *** 2008-02-26 10:10:30.974
ksedmp: internal or fatal error SnapView™: internal or fatal error
EMC PANIC: exception encountered: core dump [kpopfr()+673] [SIGFPE] [EMC Snapshot - division by zero] [0x4000000001EB4AE1] [] [] EMC PANIC: exception encountered: core dump [kpopfr () +673] [SIGFPE] [EMC Snapshot - division by zero] [0x4000000001EB4AE1]
Workaround: Press the power-off button - EMC
Solution: Call NetApp
All the best
neto
NetApp - I love this company!
0x=4
x=4/0
0x4/0=4
4=4
Posted by: venousto | August 10, 2008 at 05:24 AM
http://phebus.journalintime.com/forum/2006-05-02-zero
Posted by: venousto | August 10, 2008 at 05:59 AM
This says it all, (i took out performance though ;) >
Snapshot: EMC versus NetApp
EMC - tests (SnapView™ enabled)
NetApp - Performance tests (Snapshot™enabled)
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