Analyzing Hydra Historical Statistics Part 2

Transcription

1 Analyzing Hydra Hitorical Statitic Part Fabio Maimo Ottaviani EPV Technologie White paper 5 hnode HSM Hitorical Record The hnode i the hierarchical data torage management node and ha to perform all the management of logical tape volume reiding in the Tape Volume Cache (TVC), pre-migrated 1 or migrated to a phyical tape after they have been created or altered by the hot ytem through a vnode. Only the hnode i aware of phyical tape reource and the relationhip between the logical volume and phyical volume. It i alo reponible for any replication of the logical volume and their attribute acro ite boundarie (in the grid). Cluter Cluter 1 TVC vnode hnode LAN / WAN vnode hnode TVC TAPE LIB TAPE LIB Figure Similarly to vnode, the hnode record allow the identification of the hnode by the Node ID field and provide additional information on the hardware characteritic uch a: Machine Type, Machine Model, Machine Serial and VE (Virtualization Engine) Code Level. The information provided by the hnode HSM hitorical tatitic can be grouped in the following topic: Throttling, Logical Mount, TVC uage. 1 When a logical volume i written or updated in the TVC it i copied to real tape but it remain in the TVC to potentially improve ubequent requet performance; when the Hydra need TVC pace the logical volume i migrated (deleted from the TVC). Only the hnode that i currently in charge of TVC management will provide thi information. Analyzing Hydra Hitorical Statitic 1

2 5.1 Throttling In order to avoid hot activity that could monopolize all the TVC reource and top other tak (uch a pre-migrate and grid replication), the Hydra may introduce a delay in the repone to hot write operation. Thi i called throttling 3. The mot important metric provided are: Average Write Overrun Throttle i the delay introduced becaue the TVC free pace i going to be exhauted by an exceive write activity; Average Copy Throttle, i the delay introduced becaue the TVC i full of uncopied data to be written to other cluter; it applie only to a grid configuration. Both of them are in thouandth of a econd. 5. Logical Mount The Hydra architecture provide the poibility to plit the TVC in up to partition in the future but only one partition i ued at the moment. So the partition ize i normally the ame a the total TVC ize. All the metric decribed in thi chapter refer to partition. Logical mount requet can be claified in the following type: Mount of a cratch virtual volume; Mount of a pecific virtual volume. Mounting a cratch virtual volume normally mean opening a new volume and writing to it. Thi i normally aociated with the fat ready attribute which allow for a very quick mount often performed in le than 1 econd. When a pecific virtual volume i mounted, two different event may occur: the volume could till be in the TVC, or the volume may already have been migrated to phyical tape. In the firt cae you get what i called a cache hit mount while in the econd cae you get a cache mi mount. If you get a cache mi a recall operation i needed; thi mean that a real cartridge ha to be mounted in the tape library and the required virtual volume ha to be read in the TVC. From the performance point of view (mount time) a cache hit i very imilar to a fat ready mount. By contrat a cache mi mount i normally a much longer proce; the time to perform a recall i uually ome minute. The following graph how a comparion of the hourly number of Fat Ready (FRDYMT), Cache Hit (CAHTMT) and Cache Mi (CAMIMT) mount by cluter. 3 High level of throttling can caue a reduction in hot write activity, which may reult in elongated or erratic job run time. Analyzing Hydra Hitorical Statitic

3 1. Virtual Mount by type Grid m o u n t Cluter Cluter FRDYMT CAHTMT CAMIMT Figure 9 You can ee that mot of fat ready mount are performed by Cluter. They are concentrated in the overnight period. A lot of cache mi mount are alo requeted on Cluter while on Cluter1 mot of the mount belong to the cache hit type. The next graph how the mount time fat ready and cache hit mount in the two cluter.,5 AVG Virtual Mount Time Fat Ready and Cache Hit mount Grid 135 e c o n d 1,5 1 Cluter Cluter 1, AVFRMT AVHTMT Figure 1 Analyzing Hydra Hitorical Statitic 3

4 The average mount time i normally le than 1 econd. The highet value i for fat ready mount in Cluter 1 between 9: and 1: in the morning when only fat ready mount have been requeted. In Figure 11 the average mount time for cache mi mount i preented. AVG Virtual Mount Time Cache Mi mount Grid e c o n d 5 3 Cluter Cluter AVMIMT Figure 11 Cluter how very high value in ome hour with a peak of more than 7 econd for all the cache mi mount performed between 9: and 1: in the morning. Cache mi mount time how a ignificant correlation with the number of cache mi mount (ee Figure 9) which eem to be exceive in the peak hour. Cluter 1 i doing le activity o the average cache mi mount time i normally very table at around 1 econd. 5.3 TVC uage The Hydra architecture provide the poibility to plit the TVC in up to partition in the future but only one partition i ued at the moment. So the partition ize i normally the ame a the total TVC ize. All the metric decribed in thi chapter refer to partition. You can ue DFSMS policy management to aign virtual volume to the following preference group: the Preference Group attribute i aigned to virtual volume that are unlikely to be acceed after being created; there i no need to keep them in cache any longer than neceary o the Hydra give them preference to be copied to phyical tape when TVC pace The cale ued in the graph in Figure 9 prevent appreciation of the number of fat ready mount in Cluter 1. Analyzing Hydra Hitorical Statitic

5 i needed (or when the Hydra ha ome idle time); once a virtual volume have been copied to phyical volume it i removed from the TVC; the Preference Group 1 attribute i aigned to volume that are likely to be acceed after being created, for example volume that contain file created a part of the nightly batch run which are likely to be ued a input for the following night batch run; it would be beneficial for them to tay in the TVC for a long a poible; when pace i needed in the cache, the Hydra firt check if there are Preference Group volume that can be removed; if thi i not the cae, it elect Preference Group 1 volume to be removed baed on a leat recently ued algorithm; volume that have been copied to phyical tape (pre migrated) and have been in cache the longet without acce are removed firt. The following metric are provided for each preference group: Virtual Volume in Cache i the number of virtual volume reiding in the TVC partition, including pre-migrated volume; Data Reident in Cache i the total ize of all the virtual volume reiding in the TVC, partition including the pre-migrated volume, in MB. In Figure 1 the Data Reident in Cache value for both Performance Group (PG ) and Performance Group 1 (PG 1) are compared to the total ize of the TVC Partition. You can note that PG i almot irrelevant. 7.. TVC Uage by Preference Group Grid Cluter Cluter 1 M B PG SIZE PG1 SIZE TVC PARTITION SIZE Figure 1 Additional metric provided for each preference group are: Volume Migrated Lat Hour; the number of virtual volume migrated from the cache partition over the pat hour; Hour Average Cache Age; hour rolling average of cache age 5, in minute, of the virtual volume migrated out of the cache partition; 5 Cache age i meaured from when a volume i created or recalled into cache until it ha been migrated from cache. Analyzing Hydra Hitorical Statitic 5

6 Volume Migrated Lat Hour; the number of virtual volume migrated from the cache partition over the pat hour; Hour Average Cache Age; hour rolling average of cache age, in minute, of the virtual volume migrated out of the cache partition; Volume Migrated Lat 35 Day; the number of virtual volume migrated from the cache partition over the pat 35 day; 35 Day Average Cache Age; 35 day rolling average of cache age, in minute, of the virtual volume migrated out of the cache partition. Thee metric can be ueful to undertand if the TVC partition ize i adequate. Preference Group 1 Hour Average Cache Age Grid Cluter Cluter 1 H O U R S Figure 13 The hour rolling average of cache age i le than hour for Preference Group 1 in Cluter ; the TVC ize doen t eem to be ufficient to upport Cluter activity; thi i probably the reaon for the high recall activity highlighted in Figure 9. Other Hydra hitorical tatitic will be dicued in the third part of thi paper. Analyzing Hydra Hitorical Statitic