After you deploy a Ceph cluster, you will probably need to perform several modifications to it occasionally. These include adding or removing new nodes, disks, or services. This chapter describes how you can achieve these administration tasks. Verify that it has a proper connection to both public and cluster networks, and that time synchronization is correctly configured.
Copy-on-write vs Redirect-on-write Snapshot Copy-on-write vs Redirect-on-write Posted on April 1, by wcurtispreston There are two very different ways to create snapshots: If IT is considering using the snapshot functionality of their storage system, it is essential to understand which type of snapshot it creates and the pros and cons of using either method.
Rather than the more common term volume, this column will use the term protected entity to refer to the entity being protected by a given snapshot.
Their snapshots may be designed to protect other entities, including containers, a NAS share, etc.
You can either just use redirect:write, in which case the file will be opened and immediately closed after the write, or you can bracket the write calls by redirect:open and redirect:close, in which case the file will be kept open . You can instead write the output to a file: xsltproc regardbouddhiste.com regardbouddhiste.com > regardbouddhiste.com Another useful command-line tool is 'xmllint,' which can be used to prettify an XML file. “Like the copy-on-write method, the redirect-on-write method is a quick method for creating a shadow copy, because it copies only changes to the data. The copied blocks in the diff area can be combined with the unchanged data on the original volume to create a complete, up-to-date copy of the data.
What all snapshot types have in common is that they are virtual copies not physical copies. If something happens to the protected entity, then the snapshot will be useless.
For example, if there is a triple disk failure on a RAID 6 volume, snapshots will not help. An object storage system should also protect against a certain number of simultaneous failures. But if it exceeds that number, snapshots will not help.
A snapshot has two primary purposes: In order for the snapshot to protect against media failure, you must replicate or back it up to some other device. In other words, you must make a physical copy.
With a snapshot, nothing significant happens on the collection of hard drives where the protected entity resides. The storage system merely takes note that the way the protected entity looks at that moment means it needs preserving.
The difference between copy-on-write and redirect-on-write snapshots is how they store the previous version of a modified block, and these two methods have serious performance ramifications. Consider a copy-on-write system, which copies any blocks before they are overwritten with new information i.
In other words, if a block in a protected entity is to be modified, the system will copy that block to a separate snapshot area before it is overwritten with the new information. Prior to overwriting a block, its previous value must be read and then written to a different location, followed by the write of the new information.
If a process attempts to read the snapshot at some point in the future, it accesses it through the snapshot system that knows which blocks changed since the snapshot was taken. If a block has not been modified, the snapshot system will read that block from the original protected entity. If it has been modified, the snapshot system knows where the previous version of that block is stored and will read it from there.
This decision process for each block also comes with some computational overhead.
A redirect-on-write system uses pointers to represent all protected entities. If a block needs modification, the storage system merely redirects the pointer for that block to another block and writes the data there i. The snapshot system knows where all of the blocks are that comprise a given snapshot; in other words, it has a list of pointers and knows the location of the blocks those pointers are referring to.
If a process attempts to access a given snapshot, it simply uses these pointers to access those blocks where they originally resided. The fact that some of those blocks were replaced and are now represented by other pointers is irrelevant to the snapshot process. There is zero computational overhead of reading a snapshot in a redirect-on-write system.
Copy-on-write systems can therefore have a big impact on the performance of the protected entity. The more snapshots are created and the longer they are stored, the greater the impact to performance on the protected entity.Nov 01, · My previous question was how to redirect to an external URL from an action in the Seam way (not using FacesContext).
The answer to that was to use regardbouddhiste.comce().redirectToExternalURL(url) if using trunk (it's . “Like the copy-on-write method, the redirect-on-write method is a quick method for creating a shadow copy, because it copies only changes to the data.
The copied blocks in the diff area can be combined with the unchanged data on the original volume to create a complete, up-to-date copy of the data. Hi, folks. I've tried to use docbook2odf for my needs and the only problem for the first time is the following: I'm using it with documents, written in russian language (utf-8, of course).
To configure XSLTProc options, open the Preferences dialog box (Options > Preferences) and go to XML > XSLT/FO/XQuery > XSLT > XSLTProc..
The options of the XSLTProc processor are the same as the ones available in the command line: Enable XInclude processing - If checked, XInclude references will be resolved when XSLTProc is used . You can either just use redirect:write, in which case the file will be opened and immediately closed after the write, or you can bracket the write calls by redirect:open and redirect:close, in which case the file will be kept open .
You can instead write the output to a file: xsltproc regardbouddhiste.com regardbouddhiste.com > regardbouddhiste.com Another useful command-line tool is 'xmllint,' which can be used to prettify an XML file.