diff --git a/block.c b/block.c
index e293907..325f727 100644
--- a/block.c
+++ b/block.c
@@ -106,8 +106,8 @@
 size_t bdrv_opt_mem_align(BlockDriverState *bs)
 {
     if (!bs || !bs->drv) {
-        /* 4k should be on the safe side */
-        return 4096;
+        /* page size or 4k (hdd sector size) should be on the safe side */
+        return MAX(4096, getpagesize());
     }
 
     return bs->bl.opt_mem_alignment;
@@ -116,8 +116,8 @@
 size_t bdrv_min_mem_align(BlockDriverState *bs)
 {
     if (!bs || !bs->drv) {
-        /* 4k should be on the safe side */
-        return 4096;
+        /* page size or 4k (hdd sector size) should be on the safe side */
+        return MAX(4096, getpagesize());
     }
 
     return bs->bl.min_mem_alignment;
diff --git a/block/io.c b/block/io.c
index e6c3639..b3ea95c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -205,7 +205,7 @@
         bs->bl.opt_mem_alignment = bs->file->bl.opt_mem_alignment;
     } else {
         bs->bl.min_mem_alignment = 512;
-        bs->bl.opt_mem_alignment = 512;
+        bs->bl.opt_mem_alignment = getpagesize();
     }
 
     if (bs->backing_hd) {
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 7083924..2990e95 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -301,6 +301,7 @@
 {
     BDRVRawState *s = bs->opaque;
     char *buf;
+    size_t max_align = MAX(MAX_BLOCKSIZE, getpagesize());
 
     /* For /dev/sg devices the alignment is not really used.
        With buffered I/O, we don't have any restrictions. */
@@ -330,9 +331,9 @@
     /* If we could not get the sizes so far, we can only guess them */
     if (!s->buf_align) {
         size_t align;
-        buf = qemu_memalign(MAX_BLOCKSIZE, 2 * MAX_BLOCKSIZE);
-        for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
-            if (raw_is_io_aligned(fd, buf + align, MAX_BLOCKSIZE)) {
+        buf = qemu_memalign(max_align, 2 * max_align);
+        for (align = 512; align <= max_align; align <<= 1) {
+            if (raw_is_io_aligned(fd, buf + align, max_align)) {
                 s->buf_align = align;
                 break;
             }
@@ -342,8 +343,8 @@
 
     if (!bs->request_alignment) {
         size_t align;
-        buf = qemu_memalign(s->buf_align, MAX_BLOCKSIZE);
-        for (align = 512; align <= MAX_BLOCKSIZE; align <<= 1) {
+        buf = qemu_memalign(s->buf_align, max_align);
+        for (align = 512; align <= max_align; align <<= 1) {
             if (raw_is_io_aligned(fd, buf, align)) {
                 bs->request_alignment = align;
                 break;
@@ -726,7 +727,7 @@
 
     raw_probe_alignment(bs, s->fd, errp);
     bs->bl.min_mem_alignment = s->buf_align;
-    bs->bl.opt_mem_alignment = s->buf_align;
+    bs->bl.opt_mem_alignment = MAX(s->buf_align, getpagesize());
 }
 
 static int check_for_dasd(int fd)