2014-07-22

disadvantages of ndmp

many people favor to avoid NDMP at all. I may write a separate blog on this but here are some reasons:
  • NDMP is not storage agnostic. In general you cannot backup data and restore to another array from another vendor or sometimes even another OS version.
  • NDMP requries admin privileges. No problem for backups of large systems but not nice for restores, especially if a user want's to restore a single file.
  • The majority of the backup software solutions do not index the files of the NDMP files. In TSM for example you can store a Table of Content (TOC) with the backup but if you want to restore a single file you have to load the TOC into a temporary table to work with it. This can be very time consuming.
  • NDMP doesn't really support a incremental forever strategy. That means you have to do a full backup periodically which is a no go with large filesystems at petabyte scale that contain billion of files.
stefanradtke.blogspot.com

zfs write performance

http://www.oracle.com/technetwork/server-storage/solaris10/documentation/wp-oraclezfsconfig-0510-ds-ac2-163550.pdf

Monitor disk space and memory resources.
Keep 20% free space in your Oracle Solaris ZFS storage pools. 
The following command gives the current memory size in bytes that is used as Oracle
Solaris ZFS cache:
# kstat zfs::arcstats:size
Monitor Oracle Solaris ZFS cache sizes with the above command and readjust the
zfs_arc_max parameter when needed. If the vmstat command shows always
large free memory, you can also increase the value of zfs_arc_max.
2. Use Oracle Solaris ZFS quotas and reservations to keep free space in storage
pools.
Oracle Solaris ZFS writing strategies change when the storage volume used goes over
80% of the storage pool capacity. This change can impact the performance of rewriting
data files as Oracle's main activity. Keep more than 20% of free space is suggested for
an OLTP database. Consider setting quotas on the main pool's file systems to guarantee
that 20% free space is available at all time.
For a data warehouse database, keep 20% free space in the storage pool as a general
rule. Periodically copying data files reorganizes the file location on disk and gives better
full scan response time. For a large data warehouse database, we can have a specific rule
for read-only table spaces. When the data loading phase is ended, the table space is set
to read only. We can then copy the data files of the table space in a storage pool dedicated to read-only table spaces, and for this type of usage, we can use more than
80% of the storage pool's capacity.

2014-07-21

Capacity-on-demand for exadata

  • Capacity-on-demand may only be used to decrease the number of active processor cores during initial installation. After initial configuration, the processor core count can only increase on a system, up to the maximum. It is the customer's responsibility to acquire the additional software licenses.
  • Reducing the number of active cores lowers the initial software licensing cost. It does not change the hardware cost.
  • The minimum number of processor cores that must be enabled is half of the physical cores on each processor. For Oracle Exadata Database Machine X4-2 systems, the minimum is 6 per processor (12 per database server). For Oracle Exadata Database Machine X4-8 Full Rack, the minimum is 8 per processor (64 per database server).
  • Additional cores are increased in 2-core increments per server on Oracle Exadata Database Machine X4-2, and in 8-core increments on Oracle Exadata Database Machine X4-8 Full Rack. Database servers in the same system can enable a different number of cores

2014-07-18

x4-8

theregister:

"The new silicon will sit inside Oracle's just-announced Exadata Database Machine X4-8, which has been built for Oracle's "in-memory" database refresh.
This server is "specifically optimized for a new generation of workloads: database as a service (DBaaS) and database in-memory. With up to 12 terabytes (TB) of DRAM memory, the Exadata Database Machine X4-8 can consolidate hundreds of databases and can run massive databases entirely in-memory," Oracle says.
The machine can pack in 12TB of memory per rack, 672TB of disk storage and up to 44TB of PCIe-linked flash as well."

2014-07-15

sobolani

"Copiii care, pe băncile școlii, iau prima oară contact cu „istoria omenirii”, intră în viață convinși că războaiele și revoluțiile, cu atrocitățile lor nemaipomenite, fac parte din firescul însuși al istoriei umanității omului. Noi toți ieșim din școală cu convingerea că marii cuceritori ai lumii, de la Alexandru cel Mare la Gingis Han și Napoleon,  sunt eroi aureolați de faptele lor de vitejie și de măreția geniului lor militar. Ne uităm la istoria cruzimilor noastre ca la un film de aventuri. Nici un profesor nu ne-a spus vreodată că istoria pe care ne-o predă e cu precădere povestea unui lanț de crime sistematizate ca „fapte istorice” și că cele mai multe dintre geniile războinice ale omenirii ar fi astăzi judecate pentru crime contra umanității, și nicidecum admirate și venerate pentru ușurința cu care și-au ucis semenii de dragul gloriei proprii.
Oamenii au avut oricând la îndemână pretexte tribale și zei care să le justifice hăcuirea unor confrați al căror unic păcat era că se născuseră în alt trib. Deocamdată, la capătul câtorva zeci de mii de ani de când avem date despre crâncena noastră aventură pământeană, în duelul dintre supra-gâsca umanoidă și mega-șobolanul sângeros care s-au pitit în genomul nostru, câștig de cauză pare să fi avut ultimul: până în prezent, istoria verigii care suntem noi, oamenii, a fost mai cu seamă istoria marilor ațâțători de uri partinice. Cu părul zbârlit (cât a mai rămas din el pe această treaptă a evoluției), cu ochii ieșiți din orbite și cu o bâtă (sau o bombă) în mână pornim periodic să-i găsim pe „frații noștri” care par să se fi născut numai ca să ne potolească nouă setea de linșaj."
Liiceanu G . Mirosu sobolanilor

2014-07-10

2014-06-25

disable memory balloning

http://dbakevin.blogspot.ro/2014/05/database-memory-exhausted-caused-by.html

Explanation for vmmemctl.sys:
Memory ballooning function is not related to shared/reserved setting in vmware properties.
Memory ballooning is handled through a driver (vmmemctl.sys) that is installed as part of the VMware Tools.
This driver is loaded in the guest OS to interact with the VMkernel and is leveraged to reclaim memory pages when ESX memory resources are in demand and available physical pages cannot meet. requirements.
When memory demands rise on the ESX host, the VMkernel will instruct the balloon driver to "inflate" and consume memory in the running guest OS,
forcing the guest operating system to leverage its own native memory management techniques to handle changing conditions.
Free pages are typically released first, but the guest OS may decide to page some memory out to its pagefile on the virtual disk.
The reclaimed memory is then used by ESX to satisfy memory demands of other running workloads, but will be relinquished back to the guest OS when memory demands decrease by "deflating" the balloon driver.
Balloon driver activity can be viewed either through VirtualCenter performance monitoring graphs or ESXTOP on the local host.



From the explanation, it is clear now that during issue period, memory exhausted on ESX global server, hence it grabs memory from guest OS namely our DB server. 



Below are the steps to check the ballooning from ESX host:
a. Run esxtop.
b. Type m for memory
c. Type f for fields
d. Select the letter J for Memory Ballooning Statistics (MCTL)
e. Look at the MCTLSZ value.
MCTLSZ (MB) displays the amount of guest physical memory reclaimed by the balloon driver.

Below are steps to disable memory balloon:
Disabling ballooning via the vSphere Client
To set the maximum balloon size to zero:
1. Using the vSphere Client, connect to the vCenter Server or the ESXi/ESX host where the virtual machine resides.
2. Log into the ESXi/ESX host as a user with administrative rights.
3. Shut down the virtual machine.
4. Right-click the virtual machine listed on the Inventory panel and click Edit Settings.
5. Click the Options tab, then under Advanced, click General.
6. Click Configuration Parameters.
7. Click Add row and add the parameter sched.mem.maxmemctl in the text box.
8. Click on the row next to it and add 0 in the text box.
9. Click OK to save changes.
To re-enable the balloon driver in a virtual machine:
1. Using the vSphere Client, connect to the vCenter Server or the ESXi/ESX host where the virtual machine resides.
2. Shut down the virtual machine if it is powered on.
3. SSH to the ESXi/ESX host. For more information, see Connecting to an ESX host using an SSH client (1019852).
4. Change directory to the datastore where the virtual machine's configuration file resides.
5. Back up the virtual machine's configuration file.
6. Edit the virtual machine's configuration file (virtual_machine_name.vmx) and remove this entry:
sched.mem.maxmemctl = "0"
7. Save and close the file.
8. Power on the virtual machine.
Note: You cannot remove the entry via the Configuration Parameters UI once it has been added. You must edit the configuration file (.vmx) for the virtual machine to remove the entry.
-------------------------------------------------------
Disabling ballooning via the Windows registry
To disable ballooning on the virtual machine:
Note: This procedure modifies the Windows registry. Before making any registry modifications, ensure that you have a current and valid backup of the registry and the virtual machine. For more information on backing up and restoring the registry, see the Microsoft Knowledge Base article 136393.
1. Log into the guest OS.
2. Click Start > Run, type regedit, and press Enter. The Registry Editor window opens.
3. Navigate to:
\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VMMEMCTL
4. Change the Start key from 2 to 4.
5. Save the setting and restart the guest OS.
-------------------------------------------------------
Disabling ballooning via VMware Tools uninstallation/reinstallation
1. Uninstall VMware Tools from the guest OS.
2. Reinstall VMware Tools using the Custom Settings option, and deselect the Memory Control Drivers.

2014-06-23

happyness

Fericirea=Scop + Relații Sociale + Bunăstare materială + Sănătate