You mean questions to ask a prospective employee? 1) Q: Describe the difference between RAID0,1 and 5 and name 3 SME type arrays A: 0 is plain striping typically with 32KB,64KB or 128KB stripe size. A: 1 is mirroring A: 5 is striping with parity A: HP-EVA, EMC-Clariion, HDS-Thunder, IBM-FastT 2) Asking him to describe the function of the following in a SAN switch : Nameserver - (Answer: it processes the devices in SAN and provides the zone member details to the host.) Aliasing - (Answer: attach useful names to WWN's and ports for easier management) ISL- (Answer: Inter switch Link, to join many switches together in a fabric) 3)Q: Ask them to explain oversubscription on ISL's A: Ratio of incoming connections over the ISL to the available bandwidth on the ISL. (Hint: they should state that 7:1 or less is generally accepted as good practice!!!) 4)Q: Name 4 types of SAN architecture types A: Core-edge, Full-Mesh, Partial-Mesh,Cascade 5)Q: What is the best practice for adding a new switch to and existing SAN? A: Steps below: 1) Give the switch an IP address via serial cable, and link into network 2) Log on to switch and clear down any configuration (zones, zonesets, aliases, cfg options etc..) 3) Disable all ports on the new switch 4) Same the configuration definition of the current SAN to FTP BEFORE any merge is attempted. 5) Cable up however many ISL's to the core switch (or whatever architecture you have designed) 6) Make sure all new ISL ports are either set to auto or have been manually set to E_Port. 7) If going long distance make sure both ends of the new ISL have the correct buffer credit setting and licenses. 8) Finally enable the ISL port and make sure the switch is integrated to the SAN and is see in the fabric and that no segmentation occurs. Q: Describe the composition of a fibre channel frame A: From start to finish: 1) Start of Frame Locator (1 word) 2) Frame Header (includes Destination_ID and Source_ID....24bytes/6 words) 3) Data Payload (encapsulated SCSI instructions can be 0-2112 Bytes in length. If less than 2112, then remainder upto 2112 is filled with padding ) 4) CRC (error checking 4 bytes) 5) End Of Frame (1 word) Q: Name the 7 common frabic services as defined in the ISO fibre channel standard and their Hex addresses. (Very hard question !!!! Not many outside of the vendors or certified experts will get this one!) A: FFFFFA - Management Server FFFFFB - Time Server FFFFFC - DIrectory Server FFFFFD - Fabric Controller FFFFFE - Fabric Login Controller FFFFFF - Broadcast Server FFFFF8 - Alias Server ======================================= I am a Unix admin and work as a Unix admin. However I also have an EMC certification also. A few questions that I collected from my friends for interview preparation on EMC Storage jobs: What EMC hardware have you worked on? (like DMX3/4 etc) What Fabric Switch hardware have you worked on? (like Cisco9000, Brocade 3250 etc) How will you choose between synchronous and asynchronous replication for SRDF? What is your expertise with SymCLI? ( a few command-specific questions may follow) And .. other basic stuff like: What is zoning/masking/mapping? What is the Rule of 17 concerning mapping devices to FAs? That is just a few that jumped up on my mind. Will add to the list later if I get any. ========================================== We had 10 SAN interview questions in our earlier blogpost - Answers are given below 1) What is the differerence b/w SAN and NAS ? The basic difference between SAN and NAS , SAN is Fabric based and NAS is Ethernet based. SAN - Storage Area Network NAS - Network attached Storage 2)What is a typical storage area network consists of - if we consider it for implementation in a small business setup ? If we consider any small buisenss following are essentials componets of SAN - Fabric Switch - FC Controllers - JBOD's 3)Can you briefly explain each of these Storage area components? Fabric Swictch: It's a device which interconnects multiple network devices .There are swithes starting from 16 port to 32 ports which connect 16 or 32 machine nodes etc.Vendors who manufacture these kind of switches are Brocade, McData. FC Controllers : These are Data transfer medias they will sit on PCI slots of Server,u can configure Arrays and volumes on it. JBOD: Just Bunch of Disks is Storage Box,it consists of Enclosure where set of harddrives are hosted in many combinations such SCSI drives,SAS ,FC,SATA. 4)What is the most critical component in SAN ? Each component has its own criticality with respect to buisness needs of a company. 5) Define RAID ? Which one you feel is good choice ? RAID (Redundant array of Independent Disks) is a technology to achive redundancy with faster I/O.There are Many Levels of RAID to meet different needs of the customer which are : R0,R1,R5,R10,R5. Generally customer choose R5 to achive better redundancy and speed and it is cost effective. 6)How is a SAN managed ? There are many management softwares used for managing SAN's to name a few - Santricity - IBM Tivoli Storage Manager. - CA Unicenter. - Veritas Volumemanger. 7) Which one is the Default ID for SCSI HBA ? Generally the default ID for SCSI HBA is 7. SCSI- Small Computer System Interface HBA - Host Bus Adaptor 8) How do you install device drivers for the HBA first time during OS installation ? In some scenarios you are supposed to install Operating System on the drives connected thru SCSI HBA or SCSI RAID Conrollers,but most of the OS'es will not be updated with drivers for those controllers,that time you need to supply drivers externally,if you are installing windows ,you need to press F6 during the installion of OS and provide the driver disk or CD which came along with HBA. If you are installing linux you need to type "linux dd" for installing any driver. 9) What is Array ? Array is a group of Independent physical disks to configure any Volumes or RAID volumes. 10)Can u describe atleast 3 troubleshooting scenarios which you have come across in detail ? SCENARIO 1:How do you find/debug when there is error while working SCSI devices? In our daily SAN troubleshooting there are many management and configuration tools we use them to see when there is a failure with target device or initiator device. Some time it is even hard to trouble shoot some of the things such as media errors in the drives, or some of the drives taking long time to spinnup.In such cases these utilities will not come to help.To debug this kind of information most of the controller will be implemented with 3-pin serial debug port. With serial port debug connector cable you can collect the debug information with hyper terminal software. SCENARIO 2: I am having an issue with a controller its taking lot of time to boot and detect all the drives connected how can I solve this.? There are many possibilities that might cause this problem. One of the reason might be you are using bad drives that cannot be repaired . In those cases you replace the disks with working ones. Another reason might be slots you connected your controller to a slot which might not be supported. Try to connect with other types of slots. One more probable reason is if you have flashed the firmware for different OEM’s on the same hardware. To get rid of this the flash utilities will be having option to erase all the previous and EEPROM and boot block entry option. Use that option to rectify the problem. SCENARIO 3: I am using tape drive series 700X , even the vendor information on the Tape drive says 700X, but the POST information while booting the server is showing as 500X what could be the problem? First you should make sure your hardware is of which series , you can find out this in the product website. Generally you can see this because in most of the testing companies they use same hardware to test different series of same hardware type. What they do is they flash the different series firmware. You can always flash back to exact hardware type. VIDEO SECTION : Thanks to Sun Microsystems - SunFire X4600 4-16 Way AMD Server Demo This blog is updated daily so find more tutorials on Storage Area Networking or SAN Storage Resume or System Administration Resume 1.What is SAN ? 2.What are the JOB opportunities in SAN ? 3.Which are the companies in SAN and How much they pay ? 4.How Can I Enter SAN industry ? 5.What are the tasks of a SAN professional- How will be a day in his office life? 6.How will be a SAN job interview ? 7.SAN or Storage engineer position - Interview questions : Series1 8.Real SAN Interview questions with answers: Series2 9.Answers for SAN interview questions Series1. 10.Tell me about some Job Openings in SAN or Storage industry? 11.Do You Want to see an Enterprise SAN infrastructure - Thanks to Dell - Watch this informative Video - See a High End Lab ==================== Thin provisioning (TP) is a method of optimizing the efficiency with which the available space is utilized in storage area networks (SAN). TP operates by allocating disk storage space in a flexible manner among multiple users, based on the minimum space required by each user at any given time. In the conventional storage provisioning model, also known as fat provisioning (FP), storage space is allocated beyond current needs, in anticipation of growing need and increased data complexity. As a result, the utilization rate is low. Large amounts of storage space are paid for but may never be used. In TP, these problems are eliminated while keeping overhead low. Added benefits include reduced consumption of electrical energy, smaller hardware space requirements and reduced heat generation compared with traditional networked storage systems. ===============