IBM Hub/Switch 2.10 HPSS Sizing Considerations

Chapter 2 HPSS Planning

HPSS Installation Guide September 2002 105

Release 4.5, Revision 2

This ﬁeld can be used via the COS Hints mechanism to affect COS selection.

Guideline1:This ﬁeld should generally be set to the value of the Transfer Rate ﬁeld in the storage

class that is at the top level in the hierarchy. This should always be the case if the data is being

staged on open.

Guideline 2: If a large percentage of the reads are being done from a lower level in the hierarchy,

considersetting the transfer rate based on the Transfer Rate associated with the storage class at this

lower level.

These ﬁelds can be used via the COS Hints mechanism to affect COS selection.

Guideline: StripeLength and StripeWidth hints are available in the hints mechanism. When

speciﬁedin the hints, StripeLength and StripeWidthfrom the storage class at the top level of each

hierarchy are used in the COS selection algorithm.

Each ﬁle in HPSS is assigned a family designation. A family can be assigned to a ﬁleset, then any

ﬁle created in that ﬁleset will belong to that family. The default family is family zero, which is

interpreted by the system as meaning that the ﬁle is not associated with a family. The family

designation has no effect on the placement of ﬁles on disk, but does control the tape to which the

ﬁle migrates. HPSS will select a tape that has been assigned to the ﬁle’s family when the ﬁle is

migratedto tape. If no tapes have been assigned to the family, or all tapes assigned to the family are

busy,and if other tape assignment criteria are met (e.g. max active tapes per storage class), the tape

storage server will assign a blank tape to the family and the ﬁle will migrate to it.

HPSSplaces no restriction on the values assigned to the File Family IDs, other than zero is reserved

bythe system to indicate that a ﬁle has no family association. A name must be assigned to each ﬁle

family.

Deﬁning multiple ﬁle families may have an impact on system migration performance. MPS may

have to mount a signiﬁcantly larger number of tapes to complete a migration from a disk storage

classif the ﬁles are spread across a large number of ﬁle families, compared to the number of mounts

that would be required if all the ﬁles were in the same family.

2.10 HPSS Sizing Considerations

This section will help deﬁne the amount of storage that is needed for various aspects of HPSS,

including storage for user ﬁles, user directories, and the additional metadata storage needed for

servers to control various operations on ﬁles.