HP StorageWorks Command View TL TapeAssure Analysis Template White Paper

Transcription

1 HP StorageWorks Command View TL TapeAssure Analysis Template White Paper Part Number: AD st edition: November 2010

2 HP StorageWorks Command View TL TapeAssure Analysis Template The TapeAssure Analysis Template uses data exported from Command View TL to create graphs and tables that help backup administrators answer important questions about drive and tape health, performance, and utilization. Over thirty pre-defined graphs and tables display write and read margin, host and native data transfer rates, megabytes read and written, write and read compression ratios, unloads, utilization percentages, and tape capacity. These graphs can then be customized for analysis by drive, by tape, and over time -- by day, week, day of week, month, or week of year to satisfy a variety of user needs. Figure 1: Example Graph (Excel 2010) Minimum Requirements HP StorageWorks Command View TL version 2.5 or later is required to export TapeAssure data for use in the Template. TapeAssure data can be gathered from the following HP tape libraries: EML E-Series, ESL E-Series, MSL G3, and 1/8 Autoloader. Selected standalone tape drives are also supported through the TapeAssure Service driver, available from Minimum firmware requirements apply to tape libraries and drives. For more information, please see the HP StorageWorks Command View for Tape Libraries and Interface Manager User Guide available from under Manuals.

3 The TapeAssure Analysis Template is a Microsoft Excel spreadsheet with embedded macros. The Template is compatible with Excel 2003, 2007, and In Excel 2007 and later, a custom TapeAssure tab and ribbon menu are included. Macro security settings must also be configured to allow user-selected macros to run. To enable macros in Excel 2003: From the main menu bar, select Tools > Macro > Security In the window that appears, choose the Medium setting and click OK Close and reopen Excel and the Template for settings to take effect You will now be prompted to enable or disable macros any time you open the Template To enable macros in Excel 2007: Click the Office Button, usually in the upper left corner, and select Excel Options In the window that appears, select Trust Center and click the Trust Center Settings button In the Trust Center window, select Macro Settings, click Enable all macros, and click OK Close and reopen Excel and the Template for settings to take effect. To enable macros is Excel 2010: After opening the Template, look for the Security Warning bar just below the menu ribbon and click the Enable Content button Macros are immediately enabled, with no need to close or reopen Excel NOTE: The only files opened and operated on by the Template are user-selected Tickets.csv files. No other information is gathered, and no changes are made to your computer, registry, or Office settings. NOTE: Tape barcodes must be present in order to create accurate Tape graphs. Tapes without barcodes may be displayed as (blank) in the Template. Getting Started To create graphs and tables using the TapeAssure Analysis Template, you must first export your collected TapeAssure data from Command View TL. To export this data: Launch Command View TL, click the TapeAssure tab, and click Operations > Export to CSV In the window that appears, select Actions > Export Library Data to CSV, and click Next Select the libraries (or hosts) and time period for the export, and click Next Browse to a location for the exported data to be placed, and click Next Verify the selections and click Finish Now open the TapeAssure Analysis Template file (.xlsm or.xls). If prompted, click Enable Macros (in Excel 2003). If additional prompts or messages appears, refer to the Minimum Requirements section above. The opening screen of the Template appears:

4 Figure 2: TapeAssure Analysis Template opening screen with TapeAssure tab and ribbon displayed (Excel 2010) Instructions on how to use the Template are provided on the opening screen. A Help tab at the bottom of the screen answers frequently asked questions on how to get started with the Template. To begin: Press Ctrl+Alt+g, or press Alt+F8, select the a_getstarted macro, and click Run. In Excel 2007 and later, you can also select the TapeAssure menu tab and click the Start button on the ribbon (see Figure 2 above) In the dialog box that appears, browse to the location where you saved your exported data from Command View TL and choose one of the Tickets.csv files. This is a Comma Separated Value (CSV) file that contains records of each tape unload. Though you will see other CSV files (called Drives, Tapes, and Alerts), only the Tickets.csv file contains complete data on drive and tape health, performance, and utilization When you click Open, the file type and data structure will be checked. Assuming you selected a supported file, you will be asked if you want to open another file. The Template can import data from up to 10 Tickets.csv files and produce graphs for up to 10 libraries (or hosts) simultaneously. After all desired files have been imported, you will be asked if you want to use a replacement file to substitute the default library and drive serial numbers with identifiers that are more familiar to you. Click No for now. The use of replacement files will be explained later in this paper, and also on the Help tab in the Template itself. The Template will inform you that all data has been imported and that new calculations will be performed. Click OK. Depending on the amount of data that was exported from Command View TL, the Template may take a few seconds to up to one minute to import the data and perform new calculations

5 When prompted, press Alt+F8 again to create helpful pre-defined graphs. In Excel 2007 and later, you can also select the TapeAssure menu tab and click on the Health, Performance, or Utilization buttons to create pre-defined graphs NOTE: Each Tickets.csv file contains data collected from a single library, or in the case of standalone tape drives, from a single host. Data on all drives and tapes within that library (or collected by that host) are contained in one Tickets.csv file. The library serial number is provided as part of the file name so that, for example, TapeAssure data from a library with serial number US would be stored in the US124357_Tickets.csv file. In the case of standalone tape drives, the name of the host collecting TapeAssure data is used as part of the file name. For example, TapeAssure data from a host named mytapehost would be stored in the mytapehost_tickets.csv file. Pre-Defined Graphs and Tables After opening one or more Tickets.csv files, you can use the data to create a wide variety of useful graphs. Pre-defined graph types, components, and reporting areas are categorized as follows: Type Average History Drive Health Performance Utilization Health Performance Utilization Component Tape Health Performance Utilization N/A Performance Performance Total Utilization Utilization Table 1: Reporting Areas for each graph Type and Component Within each area above, metrics and units are as follows: Area Metric Read Margin Health Write Margin Host Transfer Rate Native Transfer Rate Read Compression Ratio Performance Write Compression Ratio Megabytes Read Megabytes Written Time spent reading or writing, compared to idle time Utilization Total unloads Tape capacity Table 2: Metrics and Units for each graph Area Units % % MB/sec MB/sec Decimal ratio (e.g. 2.5) Decimal ratio Thousands of MB Thousands of MB % Decimal count % full

6 Graphs are named using the following convention: Type_Component_Area_Metric. With reference to the tables above, some example graph names include: Average_Drive_Health_Read Margin: read as Average drive health based on read margin History_Drive_Performance_Write Compression Ratio: read as History of drive performance based on write compression ratio Average_Tape_Utilization_Tape Capacity Used: read as Average tape utilization based on tape capacity used Total_Drive_Performance_Write MB: read as Total drive performance based on Megabytes Written History_Drive_Utilization_Percent: read as History of drive utilization as a percent of time spent reading or writing compared to idle time Average and Total graphs share a common format: Figure 3: Common Format of Average and Total Graphs (Excel 2010) A = Title and explanatory text with important information about interpreting the graph. This text can be edited if desired. B = Values for each drive or tape. By default, graphs are sorted from highest to lowest value. C = Color key. Filtering by drive or tape may be allowed in some graphs. D = X-Axis identifiers: Drive serial numbers or tape barcodes. Drives and tapes with no data may not be shown. Other identifiers below the drive/tape identifiers can include library serial numbers, host names, or time periods.

7 E = Explanation of each X-Axis identifier, with the top-most identifier on the left. This text can be edited if desired. F = X-Axis filters. (In Excel 2003, these filters are centered below the graph). If not present, use Excel s PivotTable Field List dialog box for filtering. G = Y-Axis units. See Tables 1 and 2 above for typical units. H = Month or Day filters, along with an explanation of Y-Axis units. (In Excel 2003, the explanation of Y-Axis units appears directly above the graph). If not present, use Excel s PivotTable Field List dialog box for filtering. This text can be edited if desired. History graphs also share a common format but they differ somewhat from the Average/Total graphs: Figure 3: Common Format of Average/Total Graphs (Excel 2010) A = Title and explanatory text with important information about interpreting the graph. This text can be edited if desired. B = Values for each drive or tape. By default, values are shown by the day of the month. C = Color key. Filtering by drive or tape is allowed. If not present, use Excel s PivotTable Field List dialog box for filtering. D = X-Axis identifiers: Typically a day of the month. Note that days with no data are not shown. Other identifiers below the day can include library serial numbers or host names. E = Explanation of each X-Axis identifier, with the top-most identifier on the left. This text can be edited if desired. F = X-Axis filters. (In Excel 2003, these filters are centered below the graph). If not present, use Excel s PivotTable Field List dialog box for filtering.

8 G = Y-Axis units. See the table above for typical units. H = Explanation of Y-Axis units, along with Month or Day filters. (In Excel 2003, the explanation of Y-Axis units appears directly above the graph). If not present, use Excel s PivotTable Field List dialog box for filtering. This text can be edited if desired. Using the Pre-Defined Graphs Using information that is collected by Command View TL and then analyzed by the TapeAssure Analysis Template, you can answer questions about drive or tape health, drive, host or SAN performance, and drive or tape utilization such as: Question Should I change my backup application configuration to use certain drives more or less often? Do I have any drives sitting idle, or drives that aren't being used to maximum capacity? Do some of my drives need cleaning? Do I have any tapes that may need to be recycled or removed from the library? How much data am I backing up? Does the amount vary over time? Am I getting the data compression I expect? Which drives have the best and worst compression ratio? Graph to Use Select "Average Drive Utilization: Percent" or Total Drive Utilization: Unloads and look for drives on the right-hand side of the sorted graph. These drives are being used the least (in the time period you selected). Select "Average Drive Health: Write Margin" or Average Drive Health: Read Margin and look for drives on the right-hand side of the sorted graph. These drives may need cleaning or diagnostic tests. NOTE: Values shown may be historical rather than recent, depending on the timeframe you selected to export and view your data Select "Average Tape Health: Write Margin" and look for tapes on the right-hand side of the sorted graph. These tapes may need to be recycled after long use. NOTE: Filtering of data is usually required to make use of Tapes graphs. See the section below titled Using Excel Filters and Pre-Defined Fields Select Total Drive Performance: Write MB or History Drive Performance: Write MB to see the Thousands of megabytes written, either per drive or over time Select "Average Drive Performance: Write Compression Ratio" or "Average Drive Performance: Read Compression Ratio". Compression ratios for each drive are shown as a decimal number. For example, a 2-to-1 compression ratio will be shown as 2.0

9 Are my hosts able to send backup data to drives as fast as the drives can receive it? To achieve by my backup window or meet service-level agreements, should I upgrade my SAN or hosts? Should I consider adding more drives to my libraries? How does drive health, performance, or utilization change over time? Could there be another application or user affecting my backups on a particular day of the week? Are there any trends in drive health, performance, or utilization that might require a change in my backup application or SAN configuration? Which tapes are full and which are empty? Select "Average Drive Performance: Native Transfer Rate". Average data transfer rates are shown in Megabytes per second (MB/sec). Compare each actual value with the maximum transfer rate that each drive supports. For example, Ultrium 1840 (LTO-4) tape drives support up to 120 MB/sec, while Ultrium 3280 (LTO-5) tape drives support up to 140 MB/sec. Host transfer rate may be limited by LAN or SAN speed, host CPU speeds, and host RAM Select any graph prefixed with "History" to show a daily average or total for any month you select. History can be shown for read and write margin (health), host and native transfer rate (performance), or utilization percent. A separate line is plotted for each drive. You can select any subset of drives through Excel's PivotTable Field List. Pop-up dialog boxes will provide detailed instructions As above, select any report prefixed with "History" to show a daily average or total for any month you select. If desired, you can change the X axis (Category field) from Day to Day of Week or Week of Year. See the section below titled Using Excel Filters and Pre-Defined Fields Select "Average Tape Utilization: Capacity Used" to create a graph showing which tapes have been the most or least full. NOTE: Filtering of data is usually required to make use of Tapes graphs. See the section below titled Using Excel Filters and Pre- Defined Fields for tips NOTE: When interpreting any of the pre-defined graphs, it is extremely important to keep the following points in mind: Whether you are viewing an Average, Total, or History graph, each Y-Axis value represents a calculated average of many data points collected over time. This is done purposely by the Template because it is best to make decisions and identify trends based on as many data points as possible. When viewing a graph for the first time, assume that its data is historical. (To see the latest alerts and status, go directly to Command View TL). By default, graphs are drawn over the entire time period for which you exported the data. For example, if a Tickets.csv file contains data for the months of January through April, that time period is used for calculations and graphs. To view data from a more narrow or more recent time period, say just April, simply use the Month or Day filters included in the graph. If these filters are not present on the graph, use Excel s PivotTable Field List dialog box for filtering. To zoom in on a single component and time period, see the section below titled Using Zoom In and Zoom Out. Also note that drives or tapes that were previously removed from a library will still be displayed in graphs that include earlier time periods.

10 Focus on relative values when examining trends or making decisions. In general, the Template can not tell you whether a single absolute value is good or bad because such decisions depend on your unique data protection environment and policies. For example, 50% Drive Utilization isn t necessarily bad if your backup jobs only run during late-night and early-morning hours. Instead, use the graphs to look for trends over time, to set baselines for future comparison, and to help optimize your SAN and backup environment around the metrics that are most important to you. If no data is available for the drives or tapes you select, in the time period you select, no values will be shown. If you need to distinguish between small or zero values and a simple lack of data points, click the Excel Sheet created for each Chart for example, Chart3 has a data table named Sheet3 and examine the Pivot Table shown. Cells showing blank or #Value have no data, while small or zero values will be shown as decimal numbers. Using Excel Filters and Pre-Defined Fields When creating graphs for hundreds of tapes or dozens of drives, it can be helpful to filter the data in order to view just those components or data points you re interested in. For example, graphing a History of Drive Performance based on Native Transfer Rate may be too cluttered when many drives are present: Figure 4: Cluttered History Graph That Needs Filtering In this example, we might be interested in a few specific drives, which we can identify by serial number on the right-hand slide of the graph. To select only those drives, and filter out the rest, simply click the drop-down box above the color key and serial number list, and select the desired drives:

11 Figure 5: Drive Serial Number Selection (Excel 2010) Selecting only a few drives results in a more readable graph: Figure 6: Clear History Graph

12 Graphs can also be filtered to show the highest or lowest values. Using the same example, a History of Drive Performance based on Native Transfer Rate, we might be most interested in which drive has the lowest native transfer rate. This may identify the need to change backup application settings, host hardware, or SAN configuration to yield better backup/restore performance on a drive. Coupled with an Average or History graph of Read or Write Margin, it may also point to a drive that simply needs cleaning. Filtering by highest/top or lowest/bottom values is done somewhat differently in Excel 2003 versus Excel 2007 or In Excel 2003, double-click on the drop-down box above the color key and serial number list to bring up the PivotTable Field dialog box: Figure 6: PivotTable Field dialog box (Excel 2003) Now click the Advanced button to bring up the Advanced Options dialog box: Figure 7: PivotTable Field Advanced Options (Excel 2003) In this dialog box, find Top 10 AutoShow, click On, select Bottom, dial the number down to 1, and click OK. In Excel 2007 and 2010, start by clicking the drop-down box above the color key and serial number list. From the dialog box shown in Figure 6, above, select Value Filters and then Top 10. The following dialog box will appear:

13 Figure 8: Top 10 Filter (Excel 2010) Now select Bottom, dial the number down to 1, and click OK. The following graph appears, clearly showing which drive has the lowest Native Transfer Rate over the time period selected: Any graph can be filtered using these methods. Figure 9: History of Native Transfer Rate for the drive with the lowest performance NOTE: After data is compressed, Ultrium 1840 (LTO-4) tape drives support up to 120 MB/sec native speed, while Ultrium 3280 (LTO-5) tape drives support up to 140 MB/sec. Host or Native Transfer Rates may be limited by tape type, LAN or SAN speed, host CPU speeds, and host RAM.

14 It can also be useful to change the Month filter in each graph to examine the health, performance, or utilization of drives or tapes for a specific Month. If a Month drop-down box appears in the upper left corner of a graph, simply click it to select the desired time period. In Excel 2007 and 2010 you can also click to the right of the Month field in the PivotTable Field List dialog box to select the desired time period. See Figure 10, below. Figure 10: PivotTable Field List (Excel 2007,2010) X-Axis values identifiers -- typically Drive Serial Numbers, Barcodes, or Days -- can also be filtered or manually modified. Filtering is done using the same drop-down methods described for Drive Serial Number and Month above: click on the X-Axis (or Category ) field at the bottom of the graph, or in the PivotTable Field List, and select the values to limit your graph. To take another example: If you only perform full backups on certain days of the week, you might want to graph your History data by Day of Week instead of by Day. This is done by manually modifying the X-Axis fields: To manually modify the X-Axis in Excel 2003: In the graph, right-click on Day (or other X-Axis field) and select Remove Field From the PivotTable Field List, locate the Day of Week item and click on it Still in the PivotTable Field List drop-down, select Category Axis and click Add Your graph will be updated to show the named days of the week in the X-Axis. (Note that the editable text label on the X-Axis does not change)

15 If the PivotTable Field List dialog box is not visible, select Tools and then Customize. In the dialog box that appears, check the box labeled PivotTable Field List and click Close. X-Axis fields can also be selected, dragged and dropped to and from the PivotTable Field List window in Excel To manually modify the X-Axis in Excel 2007 or 2010: In the PivotTable Field List, find the Axis Field box and click on Day (or other X-Axis field) and select Remove Field from the menu that appears From the PivotTable Field List, locate the Day of Week item and right-click it Select Add to Axis Fields from the menu that appears Your graph will be updated to show the named days of the week in the X-Axis. (Note that the editable text label on the X-Axis does not change) If the PivotTable Field List dialog box is not visible, select the Analyze tab under PivotChart Tools, then click the Field List button on the ribbon. Items from the Axis Fields box can also be selected, dragged and dropped to and from other areas in the PivotTable Field List in Excel 2007 and Other time-based fields such as Date, Year, or Week of Year can be added to both the X-Axis / Category area and the Filter / Page area of your graphs using the methods described above. Once added, any of these fields can be used as a filter. Replacing Library and Drive Serial Numbers with Familiar Identifiers Whenever you open one or more Tickets.csv files you will be asked if you want to also open a replacement file to substitute library and drive serial numbers with identifiers that are more familiar to you. To use this feature you must create a separate Excel file (.xls*) with two columns: Column A contains the default library or drive serial numbers that you want to replace, while Column B contains a value to substitute for the default value in that row. For example: US HU HU Johns-Library-1 Drive-1 Drive-2 After you have created and saved this Excel file, you can use it to automatically replace default IDs with your own IDs. The TapeAssure Analysis Template will read the replacement file you specify and make substitutions before analyzing the data. Your own IDs will then be displayed in all graphs and tables created using this data, making them easier to read. Use of replacement files is optional.

16 Using Zoom In and Zoom Out Two additional macros can be used to, in essence, change an Average or Total graph into a History graph, focusing on a more narrow timeframe at each stage. This can be useful when investigating a component or time period of particular interest. When viewing any Average or Total graph, press Ctrl+Alt+i to Zoom In on a single drive serial number or tape barcode, and use Ctrl+Alt+o to Zoom Out. The zoom macros can also be accessed from the macro selection menu by pressing Alt+F8. You can zoom in multiple times, selecting a single X-Axis identifier at each stage. The zoom order is: Drive or Tape <-> Month <-> Day <-> Hour <-> Drive Load Count (individual data points) When zooming, Months, Days, or Hours that have no data points will not be shown on the graph. While the X- Axis itself will update to show each new time identifier as you zoom in and out, the editable axis label or footer text will not change. NOTE: Manually adding or removing X-Axis fields may cause the zoom macros to fail. It is recommended that Zoom In and Zoom Out only be used on (unmodified) pre-defined graphs. Definitions and Tips Selected PivotTable Fields displayed in the TapeAssure Analysis Template are described below. For more information, please see the HP StorageWorks Command View for Tape Libraries and Interface Manager User Guide available from under Manuals. Barcode: The alpha-numeric barcode of each tape. Tape barcodes must be present in order to create accurate Tape graphs. Tapes without barcodes may be displayed as (blank) in the Template. Cartridge Serial Number: A unique identifier for each tape, assigned by the manufacturer. This serial number is independent of a tape s Barcode, but may be manually substituted for the Barcode field on the X- Axis if you do not use barcodes on your tapes. See the section above titled Using Excel Filters and Pre- Defined Fields for information on manually modifying the X-Axis. Clean Cycles: The number of times the drive has been cleaned since it was manufactured. (This field is not currently used in the pre-defined graphs) DA Version: Used only for debugging purposes, this field indicates the Device Analysis version used by Command View TL. Date: A date in the format dd-mmm-yy, where dd = single- or double-digit day of the month, mmm = first three letters of the month name, yy = last two digits of the year. This field may be manually added to the X- Axis if desired. See the section above titled Using Excel Filters and Pre-Defined Fields for information on manually modifying the X-Axis. Day of Week: A three-letter name for each day of the week, e.g. Sun, Mon, Tue, etc. This field may be manually added to the X-Axis as a substitute for the Day field if desired. See the section above titled Using Excel Filters and Pre-Defined Fields for information on manually modifying the X-Axis.

17 Day: A single- or double-digit day of the month, e.g. 8, 9, 10. This field is typically used as the X-Axis in History graphs, but can also be used as a filter. See the section above titled Using Excel Filters and Pre- Defined Fields for more information on filtering. Drive Current Temp Degrees: The current temperature of the drive's controller board in degrees Celsius. This value will be significantly higher than ambient temperature and depends on drive usage and air flow as well. (This field is not currently used in the pre-defined graphs) Drive Current Temp Margin: A measure of the current temperature of the tape path expressed as a percentage. 100% indicates that temperature and airflow are well within limits, while 0% indicates that temperature and airflow are on the edge of the limits. A value less than 0% may indicate that temperature and airflow have exceeded recommended limits, which could affect the functionality of the drive. (This field is not currently used in the pre-defined graphs) Drive Load Count: The total number of times that a drive has had a tape loaded into it since the drive was manufactured. This field can be used to track the number of data points used in calculating other values, specifically when using the Zoom In function. See the section above titled Using Zoom In and Zoom Out for more information. Drive Serial Number: The serial number of the tape drive for which data is being displayed. See the section above titled Replacing Library and Drive Serial Numbers with Familiar Identifiers for information on how to change these IDs in the Template. Drive Utilization: A measure of the time that a tape drive has been reading or writing (i.e. pulling tape) divided by the amount of time that the tape drive has been powered on. Expressed as percentage from 0% (always idle) to 100% (always active). Firmware Upgrades: The number of times the drive has been updated with firmware. (This field is not currently used in the pre-defined graphs) Host Transfer Rate: The estimated rate at which data was transferred to or from the host, before data reached the drive for compression. Ultrium 1840 (LTO-4) tape drives support up to 120 MB/sec native speed, while Ultrium 3280 (LTO-5) tape drives support up to 140 MB/sec. Transfer Rates may be limited by tape type, LAN or SAN speed, host CPU speeds, and host RAM. Hour: A single- or double-digit hour of the day, from 0 to 23. This field is only displayed in History By Hour graphs, or when using the zoom macros. See the section above titled Using Zoom In and Zoom Out for more information. Note that Template data is associated with the Hour in which a tape was unloaded from a drive, not necessarily with when data was actually read or written to tape. Library or Host ID: The serial number of the tape library where drives reside, or the name of the host running the TapeAssure Service for standalone tape drives. See the section above titled Replacing Library and Drive Serial Numbers with Familiar Identifiers for information on how to change these IDs in the Template. Local Time: Used only for debugging purposes, this is a textual timestamp that includes the day of the week, month, day of the month, hour, minute, second, and year of a single exported data point.

18 Month: A three-letter name of each month of the year, e.g. Jan, Feb, Mar, etc. This field is usually used as a filter in the upper left corner of a graph, but can also be controlled through the PivotTable Field List dialog box. See the section above titled Using Excel Filters and Pre-Defined Fields for more information on filtering. Native Transfer Rate: The rate at which data was transferred to or from the tape after compression by the drive. Ultrium 1840 (LTO-4) tape drives support up to 120 MB/sec native speed, while Ultrium 3280 (LTO-5) tape drives support up to 140 MB/sec. Transfer Rates may be limited by tape type, LAN or SAN speed, host CPU speeds, and host RAM. Power Cycles: The total number of drive power cycles since the drive was manufactured. (This field is not currently used in the pre-defined graphs) Read Compression Ratio: The average compression ratio of the data read from tape, expressed as a decimal number. A 2.0 (or 2-to-1) ratio is considered typical. Read Margin: A measure of the ease with which data was read back from tape. Expressed as a percentage where 100% indicates a minimal amount of error correction was used, and where 0% indicates that the maximum amount of error correction or retries were used as recommended by HP. Note that all data will have been read back correctly, unless the drive reported an error through Command View TL or through your backup application. If the margin is less than 0%, maintenance actions such as cleaning the drive or replacing the tape may be appropriate. HP recommends the use of HP media for maximum confidence. Read MB: The total megabytes of data read from a tape between the time it was loaded in a drive and the time it was unloaded. In the pre-defined graphs, Read MB is shown in Thousands of MB. Tape Load Count: The number of times this tape has been loaded into a drive. (This field is not currently used in the pre-defined graphs) Tape Used Percent: The amount of tape capacity used, expressed as a percentage of the total capacity. TimeStamp: Used only for debugging purposes, this is a timestamp of the seconds since 1970 variety. Week of Year: The numerical week of the year, from 1 to 52. This field may be manually added to the X-Axis if desired. See the section above titled Using Excel Filters and Pre-Defined Fields for information on manually modifying the X-Axis. Write Compression Ratio: The average compression ratio of the data written to tape, expressed as a decimal number. A 2.0 (or 2-to-1) ratio is considered typical. Write Margin: A measure of the ease with which high quality data has been written to tape. Expressed as a percentage where 100% indicates no additional tape has been used, and where 0% indicates that the maximum amount of tape was used as recommended by HP. Note that all data is written at high quality, unless the drive reported an error through Command View TL or through your backup application. If the margin is less than 0%, maintenance actions such as cleaning the drive or replacing the tape may be appropriate. HP recommends the use of HP media for maximum confidence.

19 Write MB: The total megabytes of data written to tape between the time it was loaded in a drive and the time it was unloaded. In the pre-defined graphs, Write MB is shown in Thousands of MB. Year: A four-digit representation of the year, e.g. 2010, 2011, This field may be manually added to the X-Axis if desired. See the section above titled Using Excel Filters and Pre-Defined Fields for information on manually modifying the X-Axis.