Information Technology Reference
In-Depth Information
Assume that
ALLONES
,
ALLTWOS
, etc. are each arrays of 2048 bytes with
the indicated value. Assume that when the program is started, all blocks
in the
tStore
have the value
ALLZEROS
.
Just before the system crashes, what is the value of
b1
and what is the
value of
b2
?
(a) In the program above, just before the system crashes, what is the
value of
b3
and what is the value of
b4
?
(b) Suppose that after the program above runs and crashes at the indi-
cated point. After the system restarts and completes recovery and
all write-backs, what are the values stored in each of blocks 1, 2, 3,
4, and 5 of the
tStore
?
PROBLEM:
[[compareperformanceof1000updatesinplacev.transaction--
fall2011exam]]
5. Go to an on-line site that sells hard disk drives, and find the largest capac-
ity disk you can buy for less than $200. Now, track down the spec sheet
for the disk and, given the disk's specied bit error rate (or unrecoverable
read rate), estimate the probability of encountering an error if you read
every sector on the disk once.
6. Suppose we dene a RAID's access cost as the number disk accesses di-
vided by the number of data blocks read or written. For each of following
configurations and workloads, what is the access cost?
(a) Workload: a series of random 1-block writes
Configuration: mirroring
(b) Workload: a series of random 1-block writes
Configuration: distributed parity
(c) Workload: a series of random 1-block reads
Configuration: mirroring
(d) Workload: a series of random 1-block reads
Configuration: distributed parity
(e) Workload: a series of random 1-block reads
Configuration:
distributed parity with groupsize G and one failed
disk
(f) Workload: a long sequential write
Configuration: mirroring
(g) Workload: a long sequential write
Configuration: distributed parity with a group size of G
