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226<h1> HDFS Quotas Guide</h1>
227<div id="minitoc-area">
228<ul class="minitoc">
229<li>
230<a href="#Name+Quotas">Name Quotas</a>
231</li>
232<li>
233<a href="#Space+Quotas">Space Quotas</a>
234</li>
235<li>
236<a href="#Administrative+Commands">Administrative Commands</a>
237</li>
238<li>
239<a href="#Reporting+Command">Reporting Command</a>
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243
244 
245<p> The Hadoop Distributed File System (HDFS) allows the administrator to set quotas for the number of names used and the
246amount of space used for individual directories. Name quotas and space quotas operate independently, but the administration and
247implementation of the two types of quotas are closely parallel. </p>
248
249
250<a name="N10010"></a><a name="Name+Quotas"></a>
251<h2 class="h3">Name Quotas</h2>
252<div class="section">
253<p> The name quota is a hard limit on the number of file and directory names in the tree rooted at that directory. File and
254directory creations fail if the quota would be exceeded. Quotas stick with renamed directories; the rename operation fails if
255operation would result in a quota violation. The attempt to set a quota will still succeed even if the directory would be in violation of the new
256quota. A newly created directory has no associated quota. The largest quota is <span class="codefrag">Long.Max_Value</span>. A quota of one
257forces a directory to remain empty. (Yes, a directory counts against its own quota!) </p>
258<p> Quotas are persistent with the <span class="codefrag">fsimage</span>. When starting, if the <span class="codefrag">fsimage</span> is immediately in
259violation of a quota (perhaps the <span class="codefrag">fsimage</span> was surreptitiously modified),
260a warning is printed for each of such violations. Setting or removing a quota creates a journal entry. </p>
261</div>
262
263
264<a name="N10029"></a><a name="Space+Quotas"></a>
265<h2 class="h3">Space Quotas</h2>
266<div class="section">
267<p> The space quota is a hard limit on the number of bytes used by files in the tree rooted at that directory. Block
268allocations fail if the quota would not allow a full block to be written. Each replica of a block counts against the quota. Quotas
269stick with renamed directories; the rename operation fails if the operation would result in a quota violation. A newly created directory has no associated quota.
270The largest quota is <span class="codefrag">Long.Max_Value</span>. A quota of zero still permits files to be created, but no blocks can be added to the files.
271Directories don't use host file system space and don't count against the space quota. The host file system space used to save
272the file meta data is not counted against the quota. Quotas are charged at the intended replication factor for the file;
273changing the replication factor for a file will credit or debit quotas. </p>
274<p> Quotas are persistent with the <span class="codefrag">fsimage</span>. When starting, if the <span class="codefrag">fsimage</span> is immediately in
275violation of a quota (perhaps the <span class="codefrag">fsimage</span> was surreptitiously modified), a warning is printed for
276each of such violations. Setting or removing a quota creates a journal entry. </p>
277</div>
278
279
280<a name="N10042"></a><a name="Administrative+Commands"></a>
281<h2 class="h3">Administrative Commands</h2>
282<div class="section">
283<p> Quotas are managed by a set of commands available only to the administrator. </p>
284<ul>
285
286 
287<li> 
288<span class="codefrag">dfsadmin -setQuota &lt;N&gt; &lt;directory&gt;...&lt;directory&gt;</span> 
289<br> Set the name quota to be <span class="codefrag">N</span> for
290each directory. Best effort for each directory, with faults reported if <span class="codefrag">N</span> is not a positive long integer, the
291directory does not exist or it is a file, or the directory would immediately exceed the new quota. </li>
292
293 
294<li> 
295<span class="codefrag">dfsadmin -clrQuota &lt;directory&gt;...&lt;director&gt;</span>
296<br> Remove any name quota for each directory. Best
297effort for each directory, with faults reported if the directory does not exist or it is a file. It is not a fault if the
298directory has no quota. </li>
299
300 
301<li> 
302<span class="codefrag">dfsadmin -setSpaceQuota &lt;N&gt; &lt;directory&gt;...&lt;directory&gt;</span> 
303<br> Set the space quota to be
304N bytes for each directory. This is a hard limit on total size of all the files under the directory tree.
305The space quota takes replication also into account, i.e. one GB of data with replication of 3 consumes 3GB of quota. N can also be specified with a binary prefix for convenience, for e.g. 50g for 50 gigabytes and
3062t for 2 terabytes etc. Best effort for each directory, with faults reported if <span class="codefrag">N</span> is
307neither zero nor a positive integer, the directory does not exist or it is a file, or the directory would immediately exceed
308the new quota. </li>
309
310 
311<li> 
312<span class="codefrag">dfsadmin -clrSpaceQuota &lt;directory&gt;...&lt;director&gt;</span>
313<br> Remove any space quota for each directory. Best
314effort for each directory, with faults reported if the directory does not exist or it is a file. It is not a fault if the
315directory has no quota. </li>
316
317 
318</ul>
319</div>
320
321
322<a name="N10076"></a><a name="Reporting+Command"></a>
323<h2 class="h3">Reporting Command</h2>
324<div class="section">
325<p> An an extension to the <span class="codefrag">count</span> command of the HDFS shell reports quota values and the current count of names and bytes in use. </p>
326<ul>
327       
328       
329<li>
330
331 
332<span class="codefrag">fs -count -q &lt;directory&gt;...&lt;directory&gt;</span>
333<br> With the <span class="codefrag">-q</span> option, also report the name quota
334value set for each directory, the available name quota remaining, the space quota value set, and the available space quota
335remaining. If the directory does not have a quota set, the reported values are <span class="codefrag">none</span> and <span class="codefrag">inf</span>.
336
337 </li>
338
339 
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