Affinity-Based Routing in Zoned Mirrored Disks

Thomasian, Alexander; Han, Chunqi

doi:10.1093/comjnl/bxh085

Cited by 6 publications

(4 citation statements)

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“…Affinity Based Routing (ABR) divides disks to inner and outer disk blocks, which are delineated by a pivot point, which is Logical Block Address -LBA on disk [97]. Numbering LBAs from the outermost disk track, requests with an LBA lower than the pivot point are sent to the disk serving reads on outer tracks and vice-versa.…”

Section: Routing Read Requests In Mirrored Disksmentioning

confidence: 99%

“…With 2s sectors it seems that the pivot point should be at sector s, but in zoned disks this would entail outer data occupying fewer cylinders than inner data blocks and hence shorter seek times and access times [44], but also see Appendix I. Several criteria to determine the pivot point in zoned disks are considered in [97].…”

Section: Routing Read Requests In Mirrored Disksmentioning

confidence: 99%

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Mirrored and hybrid disk arrays and their reliability

Thomasian¹

2018

Cluster Comput

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Basic mirroring (BM) classified as RAID level 1 replicates data on two disks, thus doubling disk access bandwidth for read requests. RAID1/0 is an array of BM pairs with balanced loads due to striping. When a disk fails the read load on its pair is doubled, which results in halving the maximum attainable bandwidth. We review RAID1 organizations which attain a balanced load upon disk failure, but as shown by reliability analysis tend to be less reliable than RAID1/0. Hybrid disk arrays which store XORed instead of replicated data tend to have a higher reliability than mirrored disks, but incur a higher overhead in updating data. Read request response time can be improved by processing them at a higher priority than writes, since they have a direct effect on application response time. Shortest seek distance and affinity based routing both shorten seek time. Anticipatory arm placement places arms optimally to minimize the seek distance. The analysis of RAID1 in normal, degraded, and rebuild mode is provided to quantify RAID1/0 performance. We compare the reliability of mirrored disk organizations against each other and hybrid disks and erasure coded disk arrays. RAID reliabilities can be compared with a shortcut reliability analysis method.

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Section: Routing Read Requests In Mirrored Disksmentioning

confidence: 99%

Section: Routing Read Requests In Mirrored Disksmentioning

confidence: 99%

Mirrored and hybrid disk arrays and their reliability

Thomasian¹

2018

Cluster Comput

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“…Simulation results show that mirrored disk performance is dominated by the local disk scheduling policy and that SQ outperforms IQ. As a further means to improve performance we consider the effect of prioritizing read requests with respect to write requests, an asymmetric data allocation scheme, referred to as a transposed allocation in [26], and the effect of replicating data more than twice. This paper is organized as follows.…”

Section: Mirrored Disk Schedulingmentioning

confidence: 99%

“…The onboard disk cache, whose size is increasing rapidly, may have a significant effect on improving performance in this case. 2 Routing (read) requests to inner and outer disk cylinders is investigated in [26]. This study uses different criteria to determine the pivot point, which delineates outer and inner cylinders.…”

Section: Requests Interpretedmentioning

confidence: 99%

Mirrored disk rouing and scheduling

Thomasian

2006

Cluster Comput

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Disk mirroring or RAID level 1 stores the same data twice, on two independent disks, to ensure that all single disk failures can be tolerated. This high storage overhead is acceptable in view of the drop in storage cost per gigabyte and rapidly increasing disk capacities. Disk access time, on the other hand, is improving at a very slow pace, so that another important advantage of disk mirroring is the doubling of the disk access bandwidth in processing read requests. Efficient routing of read requests to disks and local disk scheduling can be used to improve performance even further. We are primarily concerned with two RAID1 configurations: (i) source-initiated routing with the independent queues-IQ method; (ii) destination-initiated routing with the shared queue-SQ method. Static, dynamic, and affinity-based (AB) routing methods are used to distribute requests with the IQ method. We compare the performance of various IQ and SQ based routing policies using a random number-driven simulation. While there is some improvement in performance with the more sophisticated routing policies, performance is dominated by the local disk scheduling policy. The SQ method allows resource sharing, so that it tends to outperform the IQ based routing, but it requires the scheduler to keep track of the state of the disk drives. As a further means to improve performance, we consider the effect of prioritizing reads with respect to writes, transposed data allocation, and replicating data more than twice. Mirrored disk schedulingMajor advances in magnetic disk technology have resulted in very high areal recording densities. There has been a three order of magnitude increase in disk capacities in the last decade and a dramatic drop in the per gigabyte cost. Due to the increased linear recording density, the transfer time of small blocks of data accessed by online transaction processing-OLTP applications constitutes a small fraction of disk rotation time, so it is negligibly small compared to disk positioning time, i.e., the sum of seek time and rotational latency. The increase in disk RPMs also contributes to this effect, but more importantly to reducing the rotational latency, which for small block transfers is roughly one half of disk rotation time. The improvement in seek time is also very slow due to its mechanical nature. The overall reduction in disk positioning time is below 8% annually [5].The fact that the improvement in disk access time lags far behind the increase in disk capacities is especially important for OLTP applications, which are concerned with random accesses to small data blocks. The performance of certain benchmarks specified by the Transaction Processing Council 1 is determined by the maximum throughput, while transaction response time is below a certain threshold. Transaction response time is affected by the number of disk accesses, which are carried out on its behalf. The database buffer in main memory is effective in eliminating a 1 http://www.tpc.org.Springer

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Mirrored & hybrid arrays

Thomasian¹

2022

Storage Systems

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Affinity-Based Routing in Zoned Mirrored Disks

Cited by 6 publications

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Mirrored and hybrid disk arrays and their reliability

Mirrored and hybrid disk arrays and their reliability

Mirrored disk rouing and scheduling

Mirrored & hybrid arrays

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