sunry - Developer IT

How to use 3T SAS HDDs which aren't supported by Dell PERC 6i

- by Sunry

We bought several 3T SAS hard disks want to use with our Dell R710 server. But we found our R710 can't recognize the 3T hd, and then we dig out the raid card is PERC 6i which doesn't support it. Contacted with Dell that H700 and H800 support 3T hd, thought we can buy a H700 , but the SAS cable is not available in the market right now. And it seems very hard for us to change the raid card, also no suitable tools to tease the special screws. So I want to know if any other method to use these 3T hds instead of putting them in the warehouse? Can I low formatting it to 2TB, and plug it into Dell R710 to use? Or a SAS to USB adapter to use it as USB external disk? I just want to use them by Dell R710 even external.

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Will UUID be the same if a disk moved from one machine to another?

- by Sunry

While in Linux every disk got a UUID. I just wondering will the UUID be the same if I moved the same disk from one Linux box to another? Is it the same UUID in different machines with the same disk? Or for a disk the UUID will change with attached machine? Also a similar question: Will the UUID be the same after Linux distribution reinstalled in the same machine with the same disk? For example: First is CentOS 5, then reinstalled it to CentOS 6.

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MySQL how to sum subgroup first then sum total

- by Sunry

My data in table_1 and table_2. table_1 id_1 num ids_2 3 33 666,777,888 4 44 111,222,333 table_2 id_2 num 111 1 222 2 333 3 666 6 777 7 888 8 I only know how to do what I want with two steps: First LEFT JOIN to get: SELECT 1.id_1, sum(2.num) FROM table_1 AS 1 LEFT JOIN table_2 AS 2 on FIND_IN_SET(2.id_2, 1.ids_2) GROUP BY 1.id_1; id_1 sum(2.num) 3 6+7+8 4 1+2+3 Then LEFT JOIN with table_1 again to sum(table_1.num+sum(2.num)): id_1 sum(table_1.num+sum(table_2.num)) 3 6+7+8+33 4 1+2+3+44 Can I do it in only one SQL?

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