Re: Ls Magazine Issue 14 Everything About Me Lsm14 01
Emmanuelle Riker
The SL8500 library uses TCP/IP protocol over an Ethernet physical interface to manage and communicate with the host and ACSLS. This interface enables ACSLS to connect to and communicate with the SL8500. Before you configure ACSLS for the SL8500:
ACSLS builds its library configuration from the information reported by the library. If SL8500 components are not operational, the library information may not be reported to ACSLS, and the ACSLS configuration of the SL8500 will be incomplete.
ACSLS supports up to fifteen connections to an ACS. For example, this can be: fifteen connections to four SL8500s; two connections to each of two SL8500s; two connections to one SL8500 and two connections to two other SL8500s; three connections to two or three libraries, and so on.
When ACSLS is connected to more than one library, the connections should be through different subnets for redundancy. If one subnet fails, communication between ACSLS and the library still continues over the other subnet(s).
When ACSLS has two connections to one SL8500 HBC card, configure the SL8500 and ACSLS server routing tables, as described in "Overview". If you have only a single connection between the ACSLS server and each SL8500 library, configuring the ACSLS and SL8500 routing tables is not necessary.
To optimize library performance and minimize inter-library communication among SL8500s, connect to the libraries with the most activity. Make the first connection that you specify in acsss_config or config acs new to the SL8500 with the most activity.
IMPORTANT: Before configuring the SL8500, the elevators (Elevator Folder) must be green. If the elevators are not green, do not configure the SL8500 to ACSLS. The elevators are the logical pass-thru-ports (PTPs). Without PTPs, ACSLS will not know that the SL8500 rails are connected.
Columns indicate the horizontal location in the library. As viewed from the front of the library column and panel numbers start at the center of the drive panel (1) and sweep forward with increasing numbers.
A pop-up window provides more information, such as: VOLID, media and cartridge type (LTO, SDLT tape, and T-Series, data, cleaning, or diagnostic) for cartridges, and shows both the internal and HLI addresses for the location.
The tape drives are associated with, and belong to an LSM. To mount a cartridge tape in a different LSM, the cartridge must go through an internal pass-thru operation (in this case, the elevator) to the drive.
Beginning with ACSLS 8.4, two SL8500 CAP types are supported in ACSLS. The legacy Rotational type may have one or two 39-cell CAPs installed on each SL8500 library. The newest CAP type, the Bulk CAP, has eight 36-cell CAPS installed on each library.
Newer SL8500 libraries are designed for faster, more efficient enter and eject operations for data centers where large and frequent vaulting activities are common. There are eight Bulk CAPs on each SL8500 library, with one CAP on each side of each rail. Each CAP contains three removable 12-slot magazines.
ACSLS uses Bulk CAPs to efficiently enter and eject cartridges. Volumes entered from a CAP are moved to a slot on the same side and on the same rail as the CAP. If that side is full, an empty slot on the other side is selected. If the rail is full, an adjacent rail is selected. This strategy minimizes robotics movement and prevents contention between robots. Similarly, if ejecting.sh ejects a list of volumes, each volume is ejected to the nearest CAP among the CAPS that you specified. See "ejecting.sh".
When this variable is set to TRUE, eleven storage cells in each magazine are used for eject operations. The bottom cell in each magazine on the top three rails remains empty, and the top cell in each magazine on the bottom rail is empty. This enables you to use the empty slot as a handle. This setting does not affect behavior during enter operations.
With eight CAPs per module, there can be eight Bulk CAPs in a ten-string SL8500 configuration. In larger SL8500 complexes, CAP operations could delay mount and dismount operations when multiple enters and ejects are in progress. To mitigate this problem, the dynamic variable, LIMIT_CAP_CONCURRENT_MOVES, can limit the number of concurrent enter and eject robotic moves, allowing mounts and dismounts to proceed. To engage this feature, set the dynamic variable, LIMIT_CAP_CONCURRENT_MOVES, to TRUE using dv_config.
Before the FSE installs Bulk CAP hardware, you must remove the cartridges in the three cell array columns closest to the service door and save them outside the library. (You will reenter the cartridges after the installation is complete.)
Reason: To install Bulk CAPs, two columns of system cell arrays must be removed plus the three-pack array. Most of the storage cells in the third column becomes system cells which are no longer accessible to ACSLS.
The SL Console can display custom operator messages on the CAP Status screen that show the purpose for enters to and ejects from Bulk CAPs. These messages can also report the partition into which cartridges are being entered or the partition from which cartridges are ejected.
Each Rotational CAP has three magazines with 13 cells each. The magazines are situated each on a different rail, accessible only to the handbots on that rail. During an enter, ACSLS attempts to move cartridges from each magazine to the adjacent LSM (rail). Only if the adjacent rail is full will the volume be moved to a different rail Similarly, volumes on a given rail are ejected to the adjacent magazine on that rail.
Since the top rail (LSM 0) does not have an adjacent CAP magazine, an elevator move automatically comes into play with volumes ejected from the top rail. On enters, the top rail is not populated until a lower rail is filled to capacity. Volumes mounted to drives on the top rail eventually migrate to the top LSM when they are dismounted. Otherwise, an explicit move operation is needed to situate volumes in the LSM on the top rail. Such an extra move can be handled automatically after an enter with the watch_vols utility. See "watch_vols".
Because the single Rotational CAP serves multiple LSMs, the Rotational CAP state is not tied to the online or offline state of any LSM. The CAP can remain online whether any one or all of the adjacent LSMs are offline. Conversely, if the CAP is offline, it is not be brought online automatically when any LSM is varied online.
Even though multiple LSMs access the CAP, the SL8500 Rotational CAP is addressed as though it was in LSM 1 (such as 1,5,9,13). In a partitioned library where each partition is assigned to a different host, users must be aware that the CAP is a shared resource. A Rotational CAP becomes reserved immediately upon an enter or eject operation. Operators in shared environments should promptly fill or empty the CAP and close the door upon completion of the CAP operation. See "Library Partitioning".
Older releases of the SL8500 had reported the optional CAP as present but not operational if the second CAP was not actually installed. As a work-around, ACSLS users were instructed to keep the desired state of the non-existent CAP offline.This is no longer an issue beginning with library firmware level 6.07 and above.
During an enter, ACSLS will always try to move the cartridge to an LSM (rail) adjacent to the CAP magazine. For ejects, ACSLS will always try to eject cartridges to a CAP cell adjacent to the LSM containing the cartridge
Unlike other libraries, the SL8500 does not have CAPs defined for each LSM ID in an SL8500 library. The CAPs on an SL8500 contain LSM 1 in their CAP IDs. There are no CAPs in an SL8500 with LSM IDs 0, 2, or 3. Partitioning complicates this problem because LSM 1 (the LSM ID in the SL8500 CAP ID) may not be assigned to your partition. (Remember, the CAPs are still available to all partitions as a shared resource).
Some ACSLS clients do not query ACSLS to identify which CAPs exist and are available before selecting a CAP for an enter, eject, or audit. They may specify cap_ids that do not exist, or CAPs that are not online. For example, some ACSAPI clients assume CAPs exist for all LSM IDs. They may automatically specify a CAP with the same LSM ID as the location of cartridges or drives that they manage. Enters, ejects, or audits that specify non-existent CAP IDs will fail.
When cartridges are dismounted, ACSLS tries to avoid elevator (pass-thru) activity among LSMs by assigning a new home cell whenever the cartridges' old home cell is in a different LSM. ACSLS attempts to put the cartridge away:
Example: You have only LTO drives on LSMs 2 and 3, and you want the LTO cartridges to be located in these LSMs. When entering these cartridges, you should place them in the CAP magazines adjacent to LSMs 2 and 3. ACSLS then makes every effort to put the cartridges in the LSM that is adjacent to that CAP magazine.
How tape drives are configured in the SL8500 can minimize both elevator and PTP activity, while supporting your tape workloads. Strategies to use in determining where tape drives are located in the SL8500 include:
Cluster cartridges by workload, with enough drives to support the maximum drives needed for the workload. Separate the cartridges used by each workload on separate rails, and ensure the rail(s) dedicated to a workload has enough drives to meet the maximum concurrent mounts for the peak usage of the workload. Ensure that the rail has not only the tape cartridges for the workload, but also the scratch cartridges that will be needed.
Clustering drives and media on a single rail works until the mounts per hour threshold is reached, all drives are in use, or there are too many active cartridges to fit on a rail. When the resources needed for a workload exceeds the capacity of a rail, spread the cartridges and drives over two or more rails.
When manually placing cartridges in the library with the front access door open, library operations cease and ACSLS must perform a full audit to update the library database to match the actual contents of the library.
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