diff --git a/src/mongo/platform/bits.h b/src/mongo/platform/bits.h
index 860bfbdccedad..f3f443209024b 100644
--- a/src/mongo/platform/bits.h
+++ b/src/mongo/platform/bits.h
@@ -19,7 +19,7 @@
 
 // figure out if we're on a 64 or 32 bit system
 
-#if defined(__x86_64__) || defined(__amd64__) || defined(_WIN64) || defined(__aarch64__)
+#if defined(__x86_64__) || defined(__amd64__) || defined(_WIN64) || defined(__aarch64__) || defined(__powerpc64__)
 #define MONGO_PLATFORM_64
 #elif defined(__i386__) || defined(_WIN32) || defined(__arm__)
 #define MONGO_PLATFORM_32
diff --git a/src/mongo/util/alignedbuilder.h b/src/mongo/util/alignedbuilder.h
index 600ea1c191409..8f8064628ccc3 100644
--- a/src/mongo/util/alignedbuilder.h
+++ b/src/mongo/util/alignedbuilder.h
@@ -107,7 +107,11 @@ namespace mongo {
         unsigned len() const { return _len; }
 
     private:
+#ifndef __PPC64__
         static const unsigned Alignment = 8192;
+#else
+        static const unsigned Alignment = 65536;
+#endif
 
         /** returns the pre-grow write position */
         inline char* grow(unsigned by) {
diff --git a/src/mongo/util/logfile.cpp b/src/mongo/util/logfile.cpp
index affbba0a9dda5..14ee1aa3d1ca1 100644
--- a/src/mongo/util/logfile.cpp
+++ b/src/mongo/util/logfile.cpp
@@ -38,7 +38,6 @@
 #include "mongo/util/startup_test.h"
 #include "mongo/util/text.h"
 
-
 using namespace mongoutils;
 
 namespace mongo {
@@ -160,6 +159,11 @@ namespace mongo {
 #include <sys/stat.h>
 #include <fcntl.h>
 #include "paths.h"
+#include <sys/ioctl.h>
+
+#ifdef __linux__
+#include <linux/fs.h>
+#endif
 
 namespace mongo {
 
@@ -175,6 +179,7 @@ namespace mongo {
                     ;
 
         _fd = open(name.c_str(), options, S_IRUSR | S_IWUSR);
+        _blkSize = g_minOSPageSizeBytes;
 
 #if defined(O_DIRECT)
         _direct = true;
@@ -183,6 +188,12 @@ namespace mongo {
             options &= ~O_DIRECT;
             _fd = open(name.c_str(), options, S_IRUSR | S_IWUSR);
         }
+#ifdef __linux__
+        _blkSize = ioctl(_fd, BLKBSZGET);
+        if (_blkSize < 0) {
+            _blkSize = g_minOSPageSizeBytes;
+        }
+#endif
 #else
         _direct = false;
 #endif
@@ -238,7 +249,7 @@ namespace mongo {
 
         fassert( 16144, charsToWrite >= 0 );
         fassert( 16142, _fd >= 0 );
-        fassert( 16143, reinterpret_cast<ssize_t>( buf ) % g_minOSPageSizeBytes == 0 );  // aligned
+        fassert( 16143, reinterpret_cast<ssize_t>( buf ) % _blkSize == 0 );  // aligned
 
 #ifdef POSIX_FADV_DONTNEED
         const off_t pos = lseek(_fd, 0, SEEK_CUR); // doesn't actually seek, just get current position
diff --git a/src/mongo/util/logfile.h b/src/mongo/util/logfile.h
index 62b3c2e9c4a4c..ee1fdbf3d5a21 100644
--- a/src/mongo/util/logfile.h
+++ b/src/mongo/util/logfile.h
@@ -67,6 +67,10 @@ namespace mongo {
 #endif
         fd_type _fd;
         bool _direct; // are we using direct I/O
+
+        // Block size, in case of direct I/O we need to test alignment against the page size,
+        // which can be different than 4kB.
+        ssize_t _blkSize;
     };
 
 }