Tenho um desafio para vocês... Vejam o cenário abaixo e gostaria de
saber que conjunto de mudanças vocês implementariam primeiro. Para tomar
esta decisão são necessárias inúmeras outras informações, como politicas,
custo de não executar a mudança, etc. etc. No entanto, imaginando que a
decisão seria tomada apenas em torno do SLA, que changes vocês escolheriam
para implementar primeiro? Eu tenho minhas considerações mas gostaria de ler
a opinião de outros colegas com mais experiência que eu.
(Desculpem o texto estar em inglês...)
[ ]'s
Rodrigo
---
Consider a scenario where a service organization provides support for IT
services subject to SLAs with minimum availability clause. The client
organizations use the services to process "revenue-generating sessions" (an
example of such a service could be an e-commerce site and sessions could be
buying transactions from site visitors, for instance). The provider earns a
fixed fee for each successfully completed session and pays a penalty
whenever the associated SLA is violated. Whenever a service is down but the
associated SLA is not violated, the provider stops collecting fees on that
service since no session can be serviced. If the SLA is violated however,
besides losing the contracted fees, the provider must pay a penalty to the
client at the end of the SLA evaluation period. Figure 1 illustrates this
scenario.
Consider a scenario where a service provider offers three services: a web
auction service; an e-commerce service; and a database service. The auction
service is to be brought down due to two changes to two of its supporting
configuration items: an operating system, whose change (*change C1*) is to
be implemented in 3 hours; and, a Data Base Management System, whose version
upgrade (*change C2*) is expected to last 2 hours. The E-commerce and
database services share a firewall and run on services that are independent
from those affected by the Web Auction Service. The firewall change (*change
C3*) is expected to last 4 hours. Table 1 lists SLA parameters for these
three services at the 10th day of operations. All SLAs are evaluated monthly
(i.e., the evaluation period, T = 30 days). Figure 2 illustrates this
scenario.
*Input*
*WebAuction Service*
*E-commerce service*
*Database service*
Service throughput (session/s)
16
12
13
Fixed fee per successful session
$ 1.5
$ 0.7
$ 0.8
Penalty due to SLA violation
$ 30000.00
$ 15000.00
$ 10000.00
Contracted service Availability**
0.99
0.99
0.99
Service availability measured on day 10**
0.998
0.992
0.9998
Due to staff limitations, the change manager cannot do both *(C1,C2) *and *
C3* simultaneously. He/she must choose which set of changes to implement
first. Notice that there is no possible overlap between *C1 *and *C2*. By
just looking at the numbers in Table, what changes you should do first?
Rodrigo Rebouças
rodrigor.com
[Non-text portions of this message have been removed]
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